Assembling features of calixarene-based amphiphiles and supra-amphiphiles

Han-Wen Tian , Yan-Cen Liu and Dong-Sheng Guo *
College of Chemistry, Key Laboratory of Functional Polymer Materials (Ministry of Education), State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, China. E-mail: dshguo@nankai.edu.cn

Received 29th July 2019 , Accepted 27th September 2019

First published on 27th September 2019


Macrocyclic amphiphiles as an emerging family of artificial amphiphiles have gained considerable attention in recent years on account of their fascinating recognition and assembly properties. Benefiting from a preorganized framework, facile modification and host–guest recognition ability, calixarenes have been widely used to fabricate self-assemblies of both amphiphiles and supra-amphiphiles. In this review, we organized hundreds of reported amphiphilic calixarenes based on their structures and systematically summarized assembling features of calixarene-based amphiphiles and supra-amphiphiles. For amphiphilic calixarenes, the size and conformation of skeletons significantly affect their assembly behaviors, such as lower critical aggregation concentration (CAC) and more diverse morphology than conventional amphiphiles. Besides, we also focus on emerging topics like uniformity, compactness, and kinetic properties of calixarene aggregation. For supra-amphiphiles, the binding affinities of calixarenes endow them with the ability to induce guest assembly. In addition, complexation of guests also improves amphiphilic calixarene aggregation. The obtained assemblies not only possess the advantages of low CAC and compact packing, but also respond to various stimuli. Finally, we pointed out several research topics of calixarene-based amphiphiles and supra-amphiphiles to be further developed in the future, such as the relationship between molecular structures and assembly properties, crosslinking, co-assembly, and utilization of cavities. We hope this review could be a guidance for studying amphiphilic assemblies based on calixarenes and other macrocyclic compounds.


image file: c9qm00489k-p1.tif

Han-Wen Tian

Han-Wen Tian obtained his BS degree from Nankai University in 2016. Then he received his MSc degree in 2019 from Nankai University under the guidance of Prof. Dong-Sheng Guo. Currently he is a PhD candidate at Nankai University. His research interest includes the design and synthesis of calixarene-based amphiphiles and recognition and assembly properties of macrocyclic amphiphiles.

image file: c9qm00489k-p2.tif

Yan-Cen Liu

Yan-Cen Liu obtained her BS and BEng degree from Nankai University and Tianjin University respectively in 2013. She received her MSc degree in 2016 from Nankai University under the guidance of Prof. Dong-Sheng Guo. Currently she is a PhD candidate at Jacobs University Bremen, Germany. Her research interest includes calixarene and cucurbituril based supramolecular chemistry.

image file: c9qm00489k-p3.tif

Dong-Sheng Guo

Dong-Sheng Guo obtained his PhD degree from Nankai University under the guidance of Prof. Yu Liu in 2006. Then he joined Prof. Liu's group as a faculty member at the College of Chemistry, Nankai University. He was promoted as an Associate Professor in 2008, and a full Professor in 2013. Since 2014, he has begun to work independently. The current research interest of his group is in supramolecular biomedical materials based on calixarenes.


1. Introduction

Amphiphiles are molecules that contain both a hydrophobic component and a hydrophilic component connected by covalent bonds.1 Inspired by nature, synthetic amphiphilic molecules enrich the concept of amphiphiles. Based on the number and properties of polar head(s)/hydrophobic tail(s) as well as their manner of connection, amphiphiles are classified as conventional amphiphiles (single head/single tail), bolaamphiphiles, gemini amphiphiles, double and triple chain amphiphiles, catanionic amphiphiles, amphiphilic polymers, etc.2 Owing to their unique structures, amphiphiles can assemble into aggregates such as micelles, vesicles, lyotropic liquid crystals, 2D monolayers and 3D multilayers,1 resulting in important biological functions and various applications in our daily life and industry.3

As an emerging family of artificial amphiphiles, macrocyclic amphiphiles have gained considerable attention in recent years on account of their fascinating recognition and assembly properties.3,4 Just as their name implies, macrocyclic amphiphiles are obtained by introducing hydrophilic groups and lipophilic groups to the preorganized scaffold. They incorporate both bola-type and gemini-type amphiphiles into a single molecule from the viewpoint of structural characteristics. Besides, the unique advantage of macrocyclic amphiphiles is the host–guest recognition. Macrocyclic amphiphiles are deemed as “surfactants with host–guest recognition sites”,5 whose macrocyclic binding sites are distributed on the surface of the amphiphilic assembly. Up to now, cyclodextrin,6 calixarene7 and pillararene8,9 have been the commonly used compounds to construct macrocyclic amphiphiles.

On the other hand, by combining supramolecular chemistry and amphiphiles, supra-amphiphiles have attracted widespread attention of scientists.10 In contrast to amphiphiles based on covalent bonds, supra-amphiphiles refer to amphiphiles constructed on the basis of noncovalent interactions or dynamic covalent bonds, which are very useful in the fabrication of nanomaterials with a high degree of structural complexity. Functional groups can be attached to supra-amphiphiles by employing various noncovalent interactions, greatly avoiding tedious covalent syntheses. Moreover, the dynamic and reversible nature of noncovalent interactions endows the resultant supramolecular architectures with excellent stimuli-responsive features. Due to their unique advantages, supra-amphiphiles are being widely and actively investigated in materials and biomedical sciences nowadays.11,12

Calixarenes are the third generation of macrocyclic compounds composed of phenolic units linked by methylene groups at the o-positions of phenolic hydroxyl groups. Their history dates back to the late nineteenth century, but they did not receive wide attention for a long time until Gutsche and coworkers studied calixarenes as mimic enzymes.13 Calixarenes have several sites for derivation and their sizes can be adjusted. Moreover, chemical modification, especially with water soluble groups, could significantly enhance their binding affinity. Benefiting from these properties, calixarenes have been described as macrocycles which have “(almost) unlimited possibilities”14 and have been widely used to fabricate amphiphiles and supra-amphiphiles. There have been a couple of reviews about calixarene-based amphiphiles and supra-amphiphiles. In 2010, Helttunena and Shahgaldian summarized self-assembly of amphiphilic calixarenes and resorcinarenes in water, and classified aggregates by their morphology.15 Later, Garcia-Rio and coworkers published a review which focuses on a promising series of calixarene, p-sulfonatocalixarene,16 while Klymchenko and coworkers focused on amphiphilic calixarenes as gene delivery vehicles.17 Recently, Guo and coworkers discussed assembly behaviors of calixarene-based amphiphiles and supra-amphiphiles, and focused on their applications in drug delivery and protein recognition.18 Up to now, calixarene-based amphiphiles and supra-amphiphiles have been widely used in many fields such as sensing,19 adsorption and extraction,20,21 catalysis,22 inorganic–organic hybrid materials,23 preparation of chiral materials24 and photoluminescent materials,25 and biomedical applications.18,26–35

In this review, we will summarize calixarene-based amphiphiles and supra-amphiphiles reported up to now and focus our special attention on their assembling features in aqueous solution. The structure of this review will be such that we first summarize and comprehensively list chemical structures of amphiphilic calixarenes, including upper-rim hydrophilic amphiphiles, lower-rim hydrophilic amphiphiles and bola-type amphiphiles, followed by their assembling features. Next we summarize the self-assemblies of calixarene-based supra-amphiphiles and their assembling features, focusing on complexation-induced aggregation (guest-induced aggregation of host, host-induced aggregation of guest, and mutual inducement).

2. Calixarene-based amphiphiles

2.1 Fabricating amphiphilic calixarenes by covalent modification

Calixarenes possess several sites which are easily modified, such as an upper rim, lower rim, and methylene bridge. As a result, more than four hundred amphiphilic calixarenes were obtained by simply modifying hydrophilic or hydrophobic groups on scaffolds. Most works focused on amphiphilic calixarenes in the cone conformation,36 in which hydrophilic and hydrophobic groups are decorated on opposite rims, resulting in upper-rim hydrophilic amphiphiles and lower-rim hydrophilic amphiphiles (Scheme 1). Moreover, the adjustable conformation of calixarenes makes it easy to modify them on the basis of an alternate conformation, or stabilize the alternate conformation after modification. The obtained compounds are bola-type amphiphiles. We comprehensively list these three classes of amphiphilic calixarenes reported up to now in Schemes 2–4 and Tables 1–3 in order to facilitate readers for following this field and further studies.
image file: c9qm00489k-s1.tif
Scheme 1 Schematic illustration of various types of calixarene-based amphiphiles.

image file: c9qm00489k-s2.tif
Scheme 2 Structures of upper-rim hydrophilic amphiphilic calixarenes.

image file: c9qm00489k-s3.tif
Scheme 3 Structures of lower-rim hydrophilic amphiphilic calixarenes.

image file: c9qm00489k-s4.tif
Scheme 4 Structures of bola-type amphiphilic calixarenes.
Table 1 References of upper-rim hydrophilic amphiphilic calixarenes in Scheme 2
Compound Ref. Compound Ref. Compound Ref. Compound Ref.
1 37 48 107 94 122 and 124 140 142 and 143
2 44 49 45, 112 and 113 95 124 141 142 and 143
3 49–59 50 45, 112 and 113 96 124 142 142, 143 and 146
4 62–66 51 117–121 97 122 143 63 and 150
5 79 52 45 98 136 144 63 and 150
6 52–54, 58, 64 and 82–89 53 108 99 136 145 150
7 64 and 95 54 108 and 128 100 139 146 63
8 53, 54, 64 and 106 55 108 101 63 and 140 147 63
9 56, 62, 82, 86, 109 and 110 56 131 102 63 148 168
10 114 57 127 and 132 103 94 149 170
11 114 and 116 58 74, 75, 127, 134 and 135 104 94 150 170
12 114 and 126 59 138 105 136 151 170
13 114 and 126 60 42 and 116 106 136 152 176
14 114 61 42 and 43 107 161 and 162 153 177
15 129 62 46 and 47 108 167 154 25 and 179
16 130 63 60 109 167 155 180 and 181
17 116 64 71–77 110 172 156 180
18 43 65 77 111 174 157 107
19 61, 104, 105 and 137 66 72 and 74–77 112 174 158 46
20 130 67 77 and 100–103 113 172 159 37
21 38–40 68 77 114 172 160 49, 59, 82, 106, 148 and 186
22 45 69 77 115 141 161 79
23 45 70 115 116 141 and 182–184 162 5, 49, 53, 54, 82, 86, 147 and 148
24 42, 45, 67–70 71 76 117 145 and 182 163 5, 37, 86, 106, 147 and 151–154
25 23 72 76 and 77 118 141 164 155
26 90 73 76 and 127 119 183 165 158
27 90 74 72 and 76 120 141 166 49 and 160
28 90 75 63 121 141 167 165 and 166
29 111 76 63 122 145 168 73
30 90 77 133 123 149 169 171
31 38 78 63 124 123 170 173
32 40 79 66 and 95 125 157 171 173
33 40 80 43 126 159 172 37
34 41 81 43 127 163 and 164 173 49
35 41 82 48 128 163 and 164 174 79
36 41 83 61 129 169 175 53 and 54
37 41 84 78 130 169 176 37 and 153
38 41 85 81 131 127 177 144
39 41 86 93 and 94 132 175 178 144
40 41 87 61, 104 and 105 133 175 179 144
41 41 88 108 134 178 180 144
42 41 89 108 135 178 181 144
43 41 90 108 136 178 182 144
44 41 91 122–125 137 185 183 144
45 80 92 124 138 185 184 156
46 91 and 92 93 124 139 185 185 156
47 92 and 96–99            


Table 2 References of lower-rim hydrophilic amphiphilic calixarenes in Scheme 3
Compound Ref. Compound Ref. Compound Ref. Compound Ref. Compound Ref.
186 49, 187 and 188 236 208 286 235 and 236 336 243 386 245
187 37 and 49 237 200 287 235 and 236 337 243 and 244 387 245
188 194 238 200, 204 and 223 288 237 338 244 388 245
189 197 239 204 and 227 289 247 339 244 389 245
190 197 240 200 290 247 340 248 390 245
191 197 241 200 and 223 291 249 341 244 391 245
192 190, 197 and 201 242 200 292 232 and 250 342 244 392 245
193 203 243 191 293 250 343 244 393 245
194 210 244 191 294 251–254 344 244 394 245
195 199 and 212 245 191 295 257 345 245 395 245
196 203 246 191 296 257 346 245 396 245
197 193 247 191 297 49 347 245 397 245
198 92 248 191 298 49 348 245 398 245
199 113 and 198 249 191 299 49 349 245 399 245
200 198 250 191 300 49 350 245 400 245
201 113 251 191 301 49 351 245 401 245
202 45, 198 and 230 252 191 302 246 352 245 402 262
203 45 253 209 303 246 353 245 403 262
204 113 and 198 254 211 304 246 354 245 404 262
205 238 255 213 305 259 355 245 405 262
206 189 256 213 306 246 356 245 406 262
207 189 257 213 307 246 357 245 407 22
208 189 258 213 308 246 358 245    
209 198 259 213 309 263 359 245    
210 102 260 213 310 264 360 245    
211 198 261 194 and 229 311 242 361 244    
212 202 and 203 262 194 and 229 312 246 362 244    
213 207 263 234 313 246 363 244    
214 207 264 234 314 246 364 244    
215 207 265 234 and 241 315 246 365 245    
216 190, 207 and 215–220 266 192 316 246 366 245    
217 190, 207, 215, 216, 219, 221 and 222 267 192 317 246 367 245    
218 190, 207 and 215–219 268 196 318 195 368 245    
219 190, 193, 201, 207, 215, 216, 225 and 226 269 196 319 255 369 256    
220 207 and 216 270 196 320 255 370 258    
221 207 and 216 271 196 321 49 371 258    
222 231 272 206 322 49 372 245    
223 233 273 206 323 244 373 245    
224 231 274 206 324 244 374 245    
225 239 and 240 275 214 325 259 375 245    
226 190 276 214 326 260 and 261 376 245    
227 193 277 214 327 244 377 245    
228 195 278 224 328 244 378 245    
229 199 279 224 329 244 379 245    
230 200 280 228 330 244 380 245    
231 200 281 228 331 248 381 245    
232 200, 204 and 205 282 188 and 232 332 198 382 245    
233 208 283 235–237 333 243 and 244 383 245    
234 208 284 235–237 334 243 384 245    
235 208 285 235 and 236 335 243 385 245    


Table 3 References of bola-type amphiphilic calixarenes in Scheme 4
Compound Ref. Compound Ref. Compound Ref. Compound Ref.
408 40 420 265 432 266 444 267
409 40 421 265 433 266 445 267
410 230 422 268 434 266 446 269
411 230 423 270 435 271 447 269
412 40 424 272 436 271 448 273
413 40 425 272 437 271 449 273
414 40 426 269 and 272 438 271 450 273
415 230 427 268 439 271 451 273
416 274 428 232 440 271 452 242 and 275–277
417 228 429 120 441 271 453 273
418 228 430 247 442 271
419 228 431 247 443 267


As we can see from the schemes, most amphiphilic calixarenes are based on calix[4]arene. Calix[5]arene, calix[6]arene, calix[8]arene, calix[9]arene, and thiacalix[4]arene are also involved. For upper-rim hydrophilic amphiphiles, almost all the common substitutions which are possible for phenols have been carried out at the upper rim. For example, a sulfonate group is widely introduced because of its excellent water-solubility and convenient one-step reaction. A nitro group and a halogen (or benzyl halide) group were also attached to the upper-rim by a one-step reaction. Further derivatization from them results in numerous functional groups such as the phosphate group, guanidinium group, carboxylic group, amino group, azide group and so on. It is noteworthy that carboxylic group and amino group could involve in amide condensation, and the azide group could react with an alkynyl compound. These well-established reactions provide the possibility of decorating calixarene with almost everything, such as cyclodextrin, PEG, saccharide, and cholesterol. On the other hand, the hydrophobic moieties of most upper-rim hydrophilic amphiphiles were introduced by alkyl halides reacting with phenolic hydroxyl at the lower rim. Meanwhile, similar nucleophilic substitution has been applied for PEG chains, resulting in lower-rim hydrophilic amphiphiles. The upper-rim attached hydrophobic chain of most lower-rim hydrophilic amphiphiles were introduced at the cyclic formation step, i.e., using p-alkylphenol as a reactant. Among them, the most popular p-alkylphenol is p-tert-butylphenol. In addition, the alkyl chain can be connected to the methylene, being introduced at the cyclic formation step as well. For bola-type amphiphiles, their conformations were usually controlled by template metal ions, for example, calix[4]arene tends to form alternative conformers in the presence of cesium carbonate. Since all these factors (skeleton, hydrophobic chain length, hydrophilic group, and conformation) affect the hydrophilic–hydrophobic balance, amphiphilic calixarenes with various assembly properties have been obtained by taking advantage of convenient synthesis.

2.2 Assembling features of amphiphilic calixarenes

2.2.1 Low critical aggregation concentration (CAC). When we study the assembly behavior of a specific amphiphile, CAC is a widely used parameter indicating self-assembling ability of amphiphiles. CAC is the concentration at which an amphiphile starts aggregating. Electrical conductivity, surface tension, light scattering and fluorescence intensity are the most commonly used parameters to determine the CAC value. Plots which show the dependence of measured physical properties on concentration of amphiphiles usually show a change of slope around CAC. CAC also relates to temperature and solvent. Under the same conditions, it is generally acknowledged that lower CAC represents stronger assembling ability, because lower CAC means lower monomer concentration in equilibrium between the monomer and assembly.3

Reported CAC values of amphiphilic calixarenes are summarized in Table 4. It is easy to notice that a large proportion of amphiphilic calixarenes have quite low CACs (<1 mM) compared with common surfactants. For example, the CACs of sodium butyl benzene sulfonate, sodium hexyl benzene sulfonate, sodium octyl benzene sulfonate, and sodium dodecyl benzene sulfonate (SDBS) are 100 mM, 30 mM, 14 mM, and 1.5 mM, respectively. The CACs of the corresponding amphiphilic calix[4]arenes 3, 6, 8, and 9 are 3.2 mM, 0.488 mM, 0.085 mM, and 0.02 mM, respectively. As a reference compound, the CAC of the gemini-type SDBS derivate is 0.9 mM. If we consider generalized monomer concentration, the CAC of the gemini-type SDBS derivate is 1.8 mM monomer, which is similar to SDBS, while the CAC of calix[4]arene 9 is 0.08 mM monomer, which is 19 times lower than that of SDBS. The lower CAC of calixarene undoubtedly originates from the cyclic oligomeric structure. From the viewpoint of entropy, amphiphiles in the assemblies have a lower degree of freedom than that in bulky water, so the entropy of amphiphiles (not including water molecules) decreases during the assembly process. The oligomer structure of calixarene leads to much lower entropy loss than the corresponding monomer, resulting in lower CAC as well as a more sensitive response to the structural difference.279

Table 4 CACs of amphiphilic calixarenes
Compound CAC (mM) Conditiona Methodb Ref.
a The condition is 25 °C in pure water if no label. I is the ionic strength. EY is Eosin Y. b ITC: isothermal titration microcalorimetry, DOSY: diffusion-ordered spectroscopy, AFM: atomic force microscopy, NMR: nuclear magnetic resonance. c The nomenclature and values of CAC1, CAC2, and CAC3 were taken from the original literature without any change.
3 2.5 30 °C Conductivity 49
3 3.05 15 °C ITC 53
3 3.20   ITC 53
3 3.40 35 °C ITC 53
3 3.73 45 °C ITC 53
3 4.16 55 °C ITC 53
3 3.18   Conductivity 54
4 (8.98 ± 2.69) × 10−2 10 mM NaCl Fluorescence 65
4 (5.84 ± 4.49) × 10−2 15 mM NaCl Fluorescence 65
4 0.566 50 mM NaCl Fluorescence 66
6 0.54   Fluorescence 84
6 0.32 D2O DOSY 84
6 0.450 15 °C ITC 53
6 0.488   ITC 53
6 0.520 35 °C ITC 53
6 0.600 45 °C ITC 53
6 0.689 55 °C ITC 53
6 0.491   Conductivity 54
6 0.040 10 mM NaCl Fluorescence 64
7 0.020 10 mM NaCl Fluorescence 64
8 0.0700 15 °C ITC 53
8 0.0850   ITC 53
8 0.0940 35 °C ITC 53
8 0.112 45 °C ITC 53
8 0.150 55 °C ITC 53
8 0.0911   Conductivity 54
9 0.02   Fluorescence 109
15 0.0285   AFM 129
21 0.65 pH 10 NaHCO3, I = 0.123 M UV-vis 38
31 0.045 pH 10 NaHCO3, I = 0.123 M UV-vis 38
31 0.035 pH 10 NaHCO3, I = 0.123 M UV-vis 38
34 1 pH 6, 20 °C Surface tension 41
34 1.3 pH 8, 20 °C Surface tension 41
35 1.6 pH 6, 20 °C Surface tension 41
35 1.3 pH 8, 20 °C Surface tension 41
36 1.3 pH 6, 20 °C Surface tension 41
36 1 pH 8, 20 °C Surface tension 41
37 1.2 pH 6, 20 °C Surface tension 41
37 1.1 pH 8, 20 °C Surface tension 41
38 1.3 pH 6, 20 °C Surface tension 41
38 1.2 pH 8, 20 °C Surface tension 41
39 1.2 pH 6, 20 °C Surface tension 41
39 1 pH 8, 20 °C Surface tension 41
40 1.2 pH 6, 20 °C Surface tension 41
40 1.1 pH 8, 20 °C Surface tension 41
41 1.2 pH 6, 20 °C Surface tension 41
41 0.2 pH 8, 20 °C Surface tension 41
42 0.1 pH 6, 20 °C Surface tension 41
42 0.4 pH 8, 20 °C Surface tension 41
43 0.5 pH 6, 20 °C Surface tension 41
43 0.1 pH 8, 20 °C Surface tension 41
44 0.1 pH 6, 20 °C Surface tension 41
44 0.1 pH 8, 20 °C Surface tension 41
46 0.023   Conductivity 91
46 0.056 pH 7 Na+/K+ PB Fluorescence 91
46 0.037 pH 9 Na+ borate Fluorescence 91
46 0.041 pH 7 Na+/K+ PB Fluorescence 91
46 0.0021 pH 9 Na+ borate Fluorescence 91
46 0.073 pH 7 Na+/K+ PB Fluorescence 91
46 0.052 pH 9 Na+ borate Fluorescence 91
46 0.04 pH 7 Na+/K+ PB Fluorescence 91
46 0.043 pH 9 Na+ borate, Fluorescence 91
47 ≤0.04 I = 0.07 M Fluorescence 98
49 0.2 D2O 1H NMR 112
57 0.01 17 °C Surface tension 132
57 0.01 30 °C Fluorescence 132
57 3.8   1H NMR 127
58 (I) 8.7   1H NMR 127
58 (Cl) 0.00879 22–23 °C Surface tension 75
58 (Cl) 9.8 22–23 °C; 30 °C UV-vis, osmolality, surface tension 134
62 0.0052   Fluorescence 46
64 0.37   Fluorescence 72
64 0.067 20 mM Tris, pH 7.4 Fluorescence 72
64 0.081 20 mM Tris, pH 7.4, 150 mM NaCl Fluorescence 72
64 4   UV-vis 73
64 0.12 0.05 mM NaCl UV-vis 73
64 0.367 22–23 °C Surface tension 75
64 0.39   Fluorescence 77
64 0.068 20 mM PB, pH 7.4 Fluorescence 77
64 0.064 20 mM PB, pH 7.4, 150 mM NaCl Fluorescence 77
65 0.026   Fluorescence 77
65 0.0098 20 mM PB, pH 7.4 Fluorescence 77
65 0.0044 20 mM PB, pH 7.4, 150 mM NaCl Fluorescence 77
66 0.048   Fluorescence 72
66 0.0062 20 mM Tris, pH 7.4 Fluorescence 72
66 0.003 20 mM Tris, pH 7.4, 150 mM NaCl Fluorescence 72
66 0.019   Fluorescence 77
66 0.0044 20 mM PB, pH 7.4 Fluorescence 77
66 0.0027 20 mM PB, pH 7.4, 150 mM NaCl Fluorescence 77
66 0.0478 22–23 °C Surface tension 75
67 0.008   Fluorescence 101
69 0.00075   Fluorescence 77
69 0.001 20 mM PB, pH 7.4 Fluorescence 77
72 0.017   Fluorescence 77
72 0.0036 20 mM PB, pH 7.4 Fluorescence 77
72 0.0030 20 mM PB, pH 7.4, 150 mM NaCl Fluorescence 77
72 0.014 20 mM acetate, pH 5 Fluorescence 77
73 1.4   1H NMR 127
74 0.01   Fluorescence 72
74 0.0029 20 mM Tris, pH 7.4 Fluorescence 72
74 0.0018 20 mM Tris, pH 7.4, 150 mM NaCl Fluorescence 72
82 0.33   Fluorescence 48
91 0.11 50 mM NaCl, pH 3.0 Fluorescence 122
91 0.042 50 mM NaCl, pH 8.0 Fluorescence 122
91 0.11 pH 8.0 Tris–HCl, 50 mM NaCl Fluorescence 123
91 0.11 pH 3.0, 50 mM NaCl UV-vis 124
94 0.0040 50 mM NaCl, pH 3.0 Fluorescence 122
97 0.0029 50 mM NaCl, pH 3.0 Fluorescence 122
98 0.0045 MES pH 6.5 Fluorescence 136
98 0.0050 MES pH 6.5 Fluorescence 136
99 0.0028 MES pH 6.5 Fluorescence 136
99 0.0050 MES pH 6.5 Fluorescence 136
101 (4.4 ± 0.2) × 10−3 50 mM NaCl, pH 3.0 Fluorescence 140
101 (1.0 ± 0.1) × 10−3 50 mM NaCl, pH 8.3 Fluorescence 140
101 (1.8 ± 0.2) × 10−3 pH 10, 50 mM NaCl Fluorescence 140
101 0.0044 pH 3.2 63
101 0.0010 pH 7.5 63
101 0.0018 pH 10 63
105 0.0064 MES pH 6.5 Fluorescence 136
105 0.79 MES pH 6.5 Fluorescence 136
106 0.0048 MES pH 6.5 Fluorescence 136
106 0.16 MES pH 6.5 Fluorescence 136
108 (1.8 ± 0.2) × 10−3 150 mM NaCl Fluorescence 167
109 (5.0 ± 1.0) × 10−4 150 mM NaCl Fluorescence 167
124 (D) 0.13 pH 8.0 Tris–HCl, 50 mM NaCl Fluorescence 123
124 (L) 0.10 pH 8.0 Tris–HCl, 50 mM NaCl Fluorescence 123
125 0.00154 50 mM NaCl Fluorescence 157
126 0.025   Fluorescence, surface tension 159
131 0.21 37 °C Relaxivity 278
132 2.3   Relaxivity 175
133 0.12   Relaxivity 175
140 0.019   Fluorescence 142
141 0.015   Fluorescence 142
142 0.013   Fluorescence 146
142 0.013   Fluorescence 142
143 0.00014 50 mM NaCl Fluorescence 150
144 0.00027 50 mM NaCl Fluorescence 150
145 0.0045 50 mM NaCl Fluorescence 150
158 0.0055   Fluorescence 46
160 1 30 °C Conductivity 49
162 0.5 30 °C Surface tension 5
162 0.67 30 °C Conductivity 5
162 0.5 30 °C Fluorescence 5
162 0.636 15 °C ITC 53
162 0.751   ITC 53
162 0.850 35 °C ITC 53
162 0.904 45 °C ITC 53
162 0.957 55 °C ITC 53
162 0.734   Conductivity 54
163 (micelle) 0.6   DLS 154
163 (domain) 1 × 10−4   DLS 154
163 (nanoassociate) 1 × 10−6   DLS 154
164 0.1   UV-vis 155
166 0.1 30 °C Surface tension 49
166 0.16 30 °C Conductivity 49
170 (7.9 ± 0.5) × 10−3   Fluorescence 173
171 (8.0 ± 0.2) × 10−3   Fluorescence 173
173 0.5 30 °C Surface tension 49
173 0.7 30 °C Conductivity 49
175 0.700 15 °C ITC 53
175 0.750   ITC 53
175 0.810 35 °C ITC 53
175 0.894 45 °C ITC 53
175 0.994 55 °C ITC 53
175 0.729   Conductivity 54
186 0.56 30 °C Surface tension 49
186 0.55 30 °C Conductivity 49
223 0.0005   UV-vis 257
230 0.4 10% DMF aqueous Surface tension 200
231 CAC1: 0.95; CAC2: 5.0c 10% DMF aqueous Surface tension 200
232 CAC2: 2.2; CAC3: 80c   Surface tension 200
232 2     205
233 2.2     208
234 2.1     208
236 2.1     208
237 0.1 10% DMF aqueous Surface tension 200
238 CAC1: 0.6; CAC2: 3.8; CAC3: 75c   Surface tension 200
238 6.5   Viscosity 200
238 CAC1: 0.95; CAC2: 6.0; CAC3: 60c 10% DMF aqueous Surface tension 200
238 27 10% DMF aqueous Viscosity 200
239 2.1     204
239 2.7     227
240 CAC1: 0.2; CAC2: 2.0; CAC3: 16c   Surface tension 200
240 78   Viscosity 200
240 CAC1: 0.95; CAC2: 7.6; CAC3: 60c 10% DMF aqueous Surface tension 200
240 CAC2: 36; CAC3: 65c 10% DMF aqueous Viscosity 200
241 CAC1: 0.18; CAC2: 4.5c   Surface tension 200
241 5.5   Viscosity 200
242 CAC1: 0.13; CAC2: 0.9c   Surface tension 200
242 2.5   Viscosity 200
261 0.51   Fluorescence 229
262 0.22   Fluorescence 229
294 0.64 D2O DOSY 252
294 1.15 D2O DOSY 254
296 0.0045   UV-vis 257
298 0.43 30 °C Conductivity 49
299 0.61 30 °C Surface tension 49
299 0.58 30 °C Conductivity 49
300 0.21 30 °C Surface tension 49
300 0.25 30 °C Conductivity 49
305 0.00579   Fluorescence 259
322 0.15 30 °C Surface tension 49
322 0.40 30 °C Conductivity 49
325 0.00305   Fluorescence 259
407 CAC1: 0.19; CAC2: 6.9c   Surface tension 22
416 0.016   Fluorescence 274
432 (91 ± 5) × 10−3 pH 7.4 Tris, pyrene Fluorescence 266
432 (2.0 ± 0.1) × 10−3 pH 7.4 Tris, EY Fluorescence 266
433 (59 ± 3) × 10−3 pH 7.4 Tris, pyrene Fluorescence 266
433 (2.6 ± 0.2) × 10−3 pH 7.4 Tris, EY Fluorescence 266
434 (33 ± 2) × 10−3 pH 7.4 Tris, pyrene Fluorescence 266
434 (2.0 ± 0.1) × 10−3 pH 7.4 Tris, EY Fluorescence 266
443 0.024   Fluorescence 267
444 0.025   Fluorescence 267
445 0.009   Fluorescence 267


For example, CACs decrease more rapidly with longer alkyl chains of amphiphilic sulfonatocalix[n]arenes (SCnAs) than that of sodium benzene sulfonate surfactants, as Basilio and co-workers proposed. They systematically investigated the relationship between CACs and the hydrophobic chain length of amphiphilic SCnAs 3, 6, and 8 from the viewpoint of thermodynamics by ITC in detail, and obtained their free energy of micellization image file: c9qm00489k-t1.tif.53,54 They proposed that the image file: c9qm00489k-t2.tif is the sum of contributions of each part of the molecule to the total free energy, such as ionic groups and counterions, aromatic rings, oxygen atoms that connect the aromatic rings to the alkyl chains, methylene group of the bridges, methylene groups of the alkyl chains, and terminal methyl groups of the chains. Among these, the free energy of transferring a methyl group from water to the micellar interior image file: c9qm00489k-t3.tif is equal to that of methylene groups image file: c9qm00489k-t4.tif add a constant (which can be represented by image file: c9qm00489k-t12.tif, in which k is a constant). Therefore, the overall contribution of alkyl chains equals the free energy change for transferring one CH2 unit from the aqueous medium to the micellar interior image file: c9qm00489k-t5.tif multiplied by the carbon number of the alkyl chain, while other parts remain constant despite the change in carbon number. So the slope of image file: c9qm00489k-t6.tif against carbon number is image file: c9qm00489k-t7.tif.53,54

Since image file: c9qm00489k-t8.tif is proportional to log CAC, we plotted log 4CAC of four amphiphilic SC4As with 4, 6, 8, 12 carbons and log CAC of the corresponding monomer, versus the number of carbon atoms in the hydrophobic chain (Fig. 1), and the slope of linear fitting is proportional to image file: c9qm00489k-t9.tif. Results show a negative slope which reflects that the hydrophobic interaction contributes more favourably to the micellization process in the presence of longer alkyl chains. More importantly, the slope of calixarenes (−0.27) is lower than the value generally observed for single-chain surfactants (−0.22), which means image file: c9qm00489k-t10.tif decreases more rapidly with longer alkyl chains of amphiphilic SCnAs than that of sodium sulfonate surfactants. This may be due to the existence of intramolecular interactions between the alkyl chains of the free monomers.53


image file: c9qm00489k-f1.tif
Fig. 1 Variation of the CAC with the number of carbons (nC) per alkyl chain for amphiphilic SC4As and alkyl benzene sulfonates.

Similar to the difference between monomers and oligomers, in general, larger size of the skeleton results in a lower degree of entropic cost,279 thus should lead to lower CAC, which is indeed supported by some reported values. For example, Shinkai and co-workers reported that in amphiphilic SCnAs 3, 160, 173, which have 4, 6, and 8 repeat units respectively, the CAC values decrease from 2.5 mM to 1.0 mM and then to 0.7 mM with increasing ring size.49 Zhao and co-workers synthesized amphiphilic calix[6]arene 305 and calix[8]arene 325 by introducing acetoxyls into the hydroxyls of calixarenes.259 They interpreted the decrease in CAC (5.79–3.05 μM) with increasing phenyl groups (6–8) as strengthening of the hydrophobic interactions. However, other examples didn’t show any significant trend. For instance, Xu and coworkers found the CAC of choline-modified calix[5]arene 158 (5.5 μM) is slightly higher than that of the corresponding calix[4]arene, 62 (5.2 μM).46 Shinkai and coworkers reported that the CACs of lower-rim sulfonic group modified 186, 299 and 322 are 0.55 mM, 0.58 mM and 0.40 mM by conductivity at 30 °C, respectively.49 These unexpected phenomena may be explained by the shape of the skeleton and the conformation in bulk solution. As an example of conformation influencing CAC, Basilio and co-workers studied amphiphilic SCnAs 6, 162 and 175. The CAC values increase (from 0.488 to 0.750 mM) with increasing number of monomeric units (from 4 to 8).54 The calix[4]arene derivative, which is preorganized into the cone conformation, is favourable for the formation of globular aggregates. The calix[6]arene and calix[8]arene derivatives do not adopt cone conformations in bulk solution. Further thermodynamic studies show that changing these conformations to the more favourable cone conformer in the aggregates implied an energetic cost that contributed to making the micellization Gibbs free energy image file: c9qm00489k-t11.tif less efficient. The other example related to conformations was reported by Arimori and coworkers.132 CAC of amphiphilic calix[4]arene 412 in a cone conformation is 10 μM whereas in a 1,3-alternate conformation, 412 could not aggregate at a concentration of even up to 10 mM. This difference implies that the conformation of calixarene is a critical factor of CAC.

On the other hand, similar to conventional surfactants, CACs of amphiphilic calixarenes are directly related to their hydrophobic/hydrophilic groups and affected by environments (temperature, pH, ionic strength and solvent).

For example, Rodik and co-workers synthesized a series of choline modified amphiphilic calixarenes 64–66 and 69 bearing various lengths of alkyl chains at the lower rim.77 They found that CACs decreased (390–0.75 μM) with the increase in the chain length (3–16 CH2 units). And we have already discussed before that CACs decrease more rapidly with longer alkyl chains.

Introducing extra interactions such as hydrogen bonds is an efficient way to enhance assembly, decreasing the CAC. Consoli and co-workers synthesized two amphiphilic calix[4]arenes 261 and 262 decorated with nucleotides at the lower rim.229 The CAC of 262 bearing adenine nucleotides (0.22 mM) is lower than that of 261 bearing thymine nucleotides (0.51 mM), which is consistent with the capacity of adenine to establish stronger stacking interactions with respect to thymine nucleobase.

High salt concentration could reduce electrostatic repulsion of like charges at the hydrophilic head group, resulting in a lower CAC value. Rodik and co-workers synthesized amphiphilic calix[4]arenes 64 and 66 bearing cationic choline groups at the upper rim and alkyl chains at the lower rim.72 Their CACs were found to be decreased from pure water (0.37 mM for 64 and 0.048 mM for 66) to 20 mM Tris buffer (0.067 mM for 64 and 0.0062 mM for 66). Mchedlov-Petrossyan and co-workers found that the CAC of 64 decreased (4–0.12 mM) with increasing concentration of NaCl as well.73

Similarly, the pH value could change the protonation states of hydrophilic heads, influencing charge interactions, resulting in a CAC change. Fujii and co-workers synthesized a new amphiphilic calix[4]arene 91 with hydrophilic amino end groups.122 With pH increasing from 3 (below the pKa of amino group) to 8 (above the pKa of amino group), the CAC decreased (from 0.11 to 0.042 mM). Further, they prepared a new calix[4]arene-based lipid 101 containing glutamic acid as the hydrophilic group.63,140 The α-amine and the γ-carboxylic acid groups of the glutamic acid moiety allowed a continuous change in the state of the head group from cationic to zwitterionic and then to anionic with increasing pH. The CAC at pH 7.5 (1.0 μM) was lower than that obtained under other pH conditions (4.4 μM at pH 3.2 and 1.8 μM at pH 10) because the intermolecular electrostatic repulsions are cancelled by the zwitterionic nature.

2.2.2 Diverse morphology. Besides CAC, morphology is another important property of amphiphilic assembly. It is not only an interesting topic in fundamental research, but also related to potential applications. NMR, DOSY, small-angle X-ray scattering (SAXS), and photo correlation spectroscopy (PCS) are methods that could be used to measure the size and shape of aggregates, while transmission electron microscopy (TEM), scanning electron microscopy (SEM), and AFM could provide us with more intuitional pictures. We summarize self-assembling morphologies of all reported amphiphilic calixarenes in aqueous solution in Table 5, which does not include Langmuir–Blodgett films formed at the air–water interface.
Table 5 Morphologies of amphiphilic calixarenes
Compound Morphologya Radiusb (nm) Conditionc Methodd Ref.
a NP: nanoparticle, SLN: solid lipid nanoparticle. b Radii are obtained from papers directly or calculated from diameters. Part of data which is not shown in papers clearly is read from figures which contain these data. Rs is the radius of the shell. Rg is the gyration radius. Rh is the hydrodynamic radius. c The condition is 25 °C in pure water if no label. CA is the corresponding amphiphilic calixarene. d SLS: static light scattering, cryo-TEM: cryogenic transmission electron microscopy, HR TEM: high resolution transmission electron microscopy, NTA: nanoparticle tracking analysis method, PGSE: pulse gradient spin echo, FE-SEM: field-emission scanning electron microscopy, EF-TEM: energy-filtered transmission electron microscopy, OPM: optical polarization microscopy, FFF-MALS: field flow fractionation combined with multi-angle light scattering.
3 Ellipsoidal micelle Minor: 1.15, major: 6.6 (prolate); 3.5 (oblate) D2O DOSY 54
4 Spherical micelle R s: 2.13; Rg: 1.64 ± 0.02 10 mM NaCl SAXS 65
4 Spherical micelle R s: 2.19; Rg: 1.73 ± 0.03 15 mM NaCl SAXS 65
6 Ellipsoidal micelle Major: 4.6 D2O DOSY 84
6 Ellipsoidal micelle Minor: 1.40, major: 8.9 (prolate); 4.6 (oblate) D2O DOSY 54
6 Spherical micelle R s: 2.40; Rg: 1.97 10 mM NaCl SAXS 64
7 Spherical micelle R s: 2.65; Rg: 2.15 10 mM NaCl SAXS 64
8 Ellipsoidal micelle Minor: 1.65, major: 7.8 (prolate); 4.3 (oblate) D2O DOSY 54
8 Spherical micelle R s: 2.10 10 mM NaCl SAXS 64
9 Micelle 6.9   DLS, AFM 109
11 Micelle 2.1–2.8 Various pH DLS 114
12 SLN 85   DLS, AFM 126
12 SLN 78 ± 1 0.1 mM NaCl DLS, AFM 126
12 SLN 81 ± 2 1 mM NaCl DLS, AFM 126
12 SLN 81 ± 1 15 mM NaCl DLS, AFM 126
12 SLN 80 ± 1 145 mM NaCl DLS, AFM 126
12 SLN 66 ± 1 0.1 mM KCl DLS, AFM 126
12 SLN 76 ± 3 1 mM KCl DLS, AFM 126
12 SLN 86 ± 1 5 mM KCl DLS, AFM 126
12 SLN 83 ± 2 140 mM KCl DLS, AFM 126
12 SLN 85 ± 1 145 mM KCl DLS, AFM 126
12 SLN 64 ± 1 0.1 mM CaCl2 DLS, AFM 126
12 SLN 60 ± 1 0.5 mM CaCl2 DLS, AFM 126
12 SLN 59 ± 1 1 mM CaCl2 DLS, AFM 126
12 SLN 105 ± 1 2 mM CaCl2 DLS, AFM 126
12 SLN 371 ± 13 2.5 mM CaCl2 DLS, AFM 126
12 SLN 1206 ± 1179 3 mM CaCl2 DLS, AFM 126
12 SLN 1429 ± 433 4 mM CaCl2 DLS, AFM 126
12 SLN 1560 ± 485 5 mM CaCl2 DLS, AFM 126
12 SLN 815 ± 1393 145 mM CaCl2 DLS, AFM 126
12 SLN 74 ± 2 0.1 mM MgCl2 DLS, AFM 126
12 SLN 64 ± 1 0.5 mM MgCl2 DLS, AFM 126
12 SLN 62 ± 1 1 mM MgCl2 DLS, AFM 126
12 SLN 104 ± 1 2 mM MgCl2 DLS, AFM 126
12 SLN 141 ± 6 2.5 mM MgCl2 DLS, AFM 126
12 SLN 507 ± 25 3 mM MgCl2 DLS, AFM 126
12 SLN 1048 ± 497 5 mM MgCl2 DLS, AFM 126
12 SLN 1247 ± 435 10 mM MgCl2 DLS, AFM 126
12 SLN 1141 ± 647 20 mM MgCl2 DLS, AFM 126
12 SLN 962 ± 1314 30 mM MgCl2 DLS, AFM 126
12 SLN 757 ± 493 145 mM MgCl2 DLS, AFM 126
13 SLN 69   DLS, AFM 126
13 SLN 69 ± 1 0.1 mM NaCl DLS, AFM 126
13 SLN 69 ± 1 1 mM NaCl DLS, AFM 126
13 SLN 68 ± 2 15 mM NaCl DLS, AFM 126
13 SLN 66 ± 2 145 mM NaCl DLS, AFM 126
13 SLN 70 ± 1 0.1 mM KCl DLS, AFM 126
13 SLN 68 ± 1 1 mM KCl DLS, AFM 126
13 SLN 65 ± 1 5 mM KCl DLS, AFM 126
13 SLN 66 ± 1 140 mM KCl DLS, AFM 126
13 SLN 66 ± 2 145 mM KCl DLS, AFM 126
13 SLN 69 ± 3 0.1 mM CaCl2 DLS, AFM 126
13 SLN 58 ± 2 0.5 mM CaCl2 DLS, AFM 126
13 SLN 52 ± 1 1 mM CaCl2 DLS, AFM 126
13 SLN 191 ± 6 2 mM CaCl2 DLS, AFM 126
13 SLN 525 ± 22 2.5 mM CaCl2 DLS, AFM 126
13 SLN 1117 ± 467 3 mM CaCl2 DLS, AFM 126
13 SLN 1345 ± 860 4 mM CaCl2 DLS, AFM 126
13 SLN 1239 ± 1172 CaCl2 5 mM DLS, AFM 126
13 SLN 1567 ± 3019 145 mM CaCl2 DLS, AFM 126
13 SLN 95 ± 65 0.1 mM MgCl2 DLS, AFM 126
13 SLN 64 ± 1 0.5 mM MgCl2 DLS, AFM 126
13 SLN 60 ± 2 1 mM MgCl2 DLS, AFM 126
13 SLN 136 ± 2 2 mM MgCl2 DLS, AFM 126
13 SLN 229 ± 20 2.5 mM MgCl2 DLS, AFM 126
13 SLN 837 ± 30 3 mM MgCl2 DLS, AFM 126
13 SLN 1365 ± 399 5 mM MgCl2 DLS, AFM 126
13 SLN 650 ± 650 10 mM MgCl2 DLS, AFM 126
13 SLN 1425 ± 256 20 mM MgCl2 DLS, AFM 126
13 SLN 848 ± 1237 30 mM MgCl2 DLS, AFM 126
13 SLN 1242 ± 625 145 mM MgCl2 DLS, AFM 126
18 Vesicle 54 ± 3 10 mM PB 7.2, 154 mM NaCl DLS 43
24 Mixture of large or small vesicles, distorted vesicles and rod-like micelles R h: 43; Rg: 58 0.1 M NH3 aqueous SLS, DLS, cryo-TEM 42
24 Liquid crystal 5 N NH3 aqueous OPM 42
24 Mixture of SLNs and lipid layers 100 (SLN)   PCS, AFM 67
25 Spherical aggregate 100–125 pH 3 FE-SEM, EF-TEM 23
25 Necklace-like aggregate 250 pH 7 FE-SEM, EF-TEM 23
26 Nanofiber 750 H2O–EtOH 9[thin space (1/6-em)]:[thin space (1/6-em)]1 DLS, FE-SEM, TEM 90
29 Multilamellar vesicle 84 ± 24   DLS, FE-SEM, TEM 111
34 Micelle pH 6 41
34 Micelle pH 8 41
35 Micelle pH 6 41
35 Micelle pH 8 41
36 Micelle pH 6 41
36 Micelle pH 8 41
37 Micelle pH 6 41
37 Micelle pH 8 41
38 Micelle pH 6 41
38 Micelle pH 8 41
39 Micelle pH 6 41
39 Micelle pH 8 41
40 Micelle pH 6 41
40 Micelle pH 8 41
41 Micelle pH 6 41
41 Micelle pH 8 41
42 Micelle pH 6 41
42 Micelle pH 8 41
43 Micelle pH 6 41
43 Micelle pH 8 41
44 Micelle pH 6 41
44 Micelle pH 8 41
46 Mixture of rod-like and spherical micelles 3.6 (rod-like); 4.2 (spherical) Na+ and K+ PB, pH 7 Cryo-TEM 91
46 Spherical micelle 3.2 Na+ borate, pH 9 Cryo-TEM 91
46 Membrane with a uniform pattern of pores pH 4 Cryo-TEM 91
47 3 pH 7.2 PGSE NMR 97
47 Hollow spherical cage 3.8 27 mM Na+ and K+ Cryo-TEM 97
47 Micelle 4.0–4.5 27 mM K+, pH 7.0 Cryo-TEM 99
47 Micelle 3.2–3.7 27 mM Na+ and K+, pH 7.0 Cryo-TEM 99
49 3.27 D2O DOSY 112
51 SLN 73 ± 3   DLS 117
57 Micellar aggregate 1–2 30 °C DLS 132
58 Vesicle 40–650   DLS, TEM 134
60 Liquid crystal   OPM 42
61 Micelle 2.7 ± 0.3 10 mM PB, pH 7.2, 154 mM NaCl DLS 43
62 Vesicle 75   DLS 46
63 Micelle 2.5 75 mM Na2SO4 DLS 60
64 Micelle ∼2   DLS 71
64 ∼2   DLS, TEM 73
64 Micelle 1.47 20 mM Tris, pH 7.4 DLS 77
65 Micelle 2.74 20 mM Tris, pH 7.4 DLS 77
66 Micelle 3.2   DLS 72
66 Micelle 2.82 20 mM Tris, pH 7.4 DLS 77
67 Micelle 20   DLS 101
67 Micelle 3.69 20 mM Tris, pH 7.4 DLS 77
68 150–200 20 mM Tris, pH 7.4 DLS 77
69 Micelle 4.14 20 mM Tris, pH 7.4 DLS 77
72 Micelle 3.04 20 mM Tris, pH 7.4 DLS 77
72 Micelle 3.28 20 mM acetate, pH 5.0 DLS 77
74 Micelle 3.2   DLS 72
75 Spherical micelle 50 mM NaCl SAXS 63
76 Spherical micelle 50 mM NaCl SAXS 63
77 Spherical micelle 50 mM NaCl SAXS 63
77 Spherical micelle 100 mM NaCl SAXS 63
77 Spherical micelle 200–300 mM NaCl SAXS 63
77 Mixture of various micellar shapes >400 mM NaCl SAXS 63
78 Spherical micelle 50 mM NaCl SAXS 63
79 Spherical micelle 50 mM NaCl SAXS 63
82 Micelle 14 0.33 mM DLS 48
82 Vesicle or aggregate of micelles 70 1 mM DLS 48
86 SLN 95   PCS 93
91 Spherical micelle pH < 6, 50 mM NaCl AFM 122
91 Mixture of rod-like and spherical micelles 3 < pH < 8, 50 mM NaCl AFM 122
91 Connected network pH = 10, 50 mM NaCl AFM 122
91 Cylindrical micelle pH 8.0, 50 mM NaCl AFM 122
91 Spherical micelle 2.05 pH 4.2, 50 mM NaCl SAXS 122
91 Cylindrical micelle 1.68 pH 7.5, 50 mM NaCl SAXS 122
91 Micelle R g: 1.67 SAXS 125
91 Spherical micelle R h: 2.05; Rg: 1.47 ± 0.11 50 mM NaCl, pH 3.0 SAXS 124
92 Spherical micelle R h: 2.10; Rg: 1.58 ± 0.15 50 mM NaCl, pH 3.0 SAXS 124
93 Spherical micelle R h: 2.25; Rg: 1.94 ± 0.17 50 mM NaCl, pH 3.0 SAXS 124
94 Spherical micelle pH < 6, 50 mM NaCl AFM 122
94 Vesicular micelle pH = 8, 50 mM NaCl AFM 122
94 Mixture of rod-like and spherical micelles pH = 6, 50 mM NaCl AFM 122
94 Cylindrical micelle pH 6.3, 50 mM NaCl AFM 122
94 Spherical micelle 2.75 pH 4.3, 50 mM NaCl SAXS 122
94 Cylindrical micelle 2.0 pH 6.3, 50 mM NaCl SAXS 122
94 Plate micelle 1.91 pH 7.8, 50 mM NaCl SAXS 122
94 Spherical micelle R h: 2.75; Rg: 2.52 ± 0.19 50 mM NaCl, pH 3.0 SAXS 124
95 Cylindrical micelle R h: 2.20; Rg: 1.70 ± 0.10 50 mM NaCl, pH 3.0 SAXS 124
96 Cylindrical micelle R h: 2.35; Rg: 1.87 ± 0.13 50 mM NaCl, pH 3.0 SAXS 124
97 Rod-like micelle pH < 6, 50 mM NaCl AFM 122
97 Cylindrical micelle 2.40 pH 4.7, 50 mM NaCl SAXS 122
98 88 ± 6 50 mM MES, pH 6.5 DLS, SLS 136
99 70 ± 27 50 mM MES, pH 6.5 DLS, SLS 136
100 Dot-like micelle 2.25 50 mM NaCl, pH 3.0 SAXS, AFM 139
101 Spherical micelle 2.15 50 mM NaCl, pH 3.0 SAXS 140
101 Spherical micelle 2.35 50 mM NaCl, pH 5.4 SAXS 140
101 Finite cylindrical micelle 1.90 50 mM NaCl, pH 6.2 SAXS 140
101 Infinite cylindrical micelle 1.80 50 mM NaCl, pH 7.4 SAXS 140
101 Infinite cylindrical micelle 1.80 50 mM NaCl, pH 8.3 SAXS 140
101 Finite cylindrical micelle 1.98 50 mM NaCl, pH 9.2 SAXS 140
101 Spherical micelle 2.38 50 mM NaCl, pH 10 SAXS 140
102 Spherical micelle 50 mM NaCl SAXS 63
105 97 ± 2 50 mM MES, pH 6.5 DLS, SLS 136
106 77 ± 9 50 mM MES, pH 6.5 DLS, SLS 136
108 Micelle R g: 1.76 150 mM NaCl DLS, SAXS, AFM 167
109 Micelle R g: 2.46 150 mM NaCl DSL, SAXS, AFM 167
123 10.1 ± 0.8 PBS DLS 149
124 Vesicle 10–30 50 mM NaCl/Tris–HCl, pH 7–8 DLS, TEM 123
125 Cylindrical micelle R h: 2.50 50 mM NaCl, pH 7.0, 25 °C SAXS 157
125 Spherical micelle R h: 2.85; Rg: 2.81 50 mM NaCl, pH 7.0, 40 °C SAXS 157
125 Spherical micelle R h: 2.72; Rg: 2.73 50 mM NaCl, pH 12, 25 °C SAXS 157
125 Spherical micelle R h: 2.58; Rg: 1.80 50 mM NaCl, pH 12, 40 °C SAXS 157
126 Globular micelle R h: 3; Rg: 2.43   DLS, SAXS 159
127 SLN 65   DLS, AFM 163
127 Nanosphere 65 ± 1   DLS, cryo-TEM 164
127 Nanocapsule 60 ± 1   DLS, cryo-TEM 164
128 SLN 95   DLS, AFM 163
128 Nanosphere 95 ± 1   DLS, cryo-TEM 164
128 Nanocapsule 76 ± 1   DLS, cryo-TEM 164
129 Vesicle 25–50   DLS, TEM 169
130 Fiber 25 (radius), several micrometers long   DLS, TEM 169
131 Micelle 2.2   DLS 278
137 Vesicle 100   DLS, TEM, FE-SEM 185
138 Vesicle 18   DLS, TEM, FE-SEM 185
138 Micelle 3 pH 5 DLS, TEM 185
139 Micelle 3   DLS, TEM 185
140 Micelle 2.9   DLS 142
140 Micelle 2.8   TEM 142
140 Irregular NP 7–16   TEM 142
141 Micelle 3.5   DLS 142
141 Micelle 3.6   TEM 142
141 Sole like NP 13–43   TEM 142
141 Solid micelle 3.6   TEM 143
142 Irregular NP 8–50   TEM 146
142 Mixture of micelles and NPs 3 (micelle); 40 (NP)   HR TEM 146
142 Mixture of micelles and NPs 3 (micelle); 25 (NP)   Cryo-TEM 146
142 Micelle 1.8   DLS 146
142 Micelle 1.8   DLS 142
142 Micelle 2.5   TEM, HR TEM, cryo-TEM 142
142 Irregular NP 8–50   TEM, HR TEM, cryo-TEM 142
142 Solid micelle 2.5   TEM 143
143 Micelle R h: 2.90; Rg: 2.26 ± 0.14 50 mM NaCl SAXS 150
144 Micelle R h: 3.60; Rg: 2.63 ± 0.12 50 mM NaCl SAXS 150
145 Micelle R h: 4.10; Rg: 3.75 ± 0.34 50 mM NaCl SAXS 150
147 Spherical micelle 50 mM NaCl SAXS 63
148 118   PCS 168
154 88 10 mM HEPES, pH 8.0 DLS 179
158 Vesicle 40   DLS 46
162 Ellipsoidal micelle Minor: 2.10, major: 3.45   SAXS 147
162 Ellipsoidal micelle Minor: 1.40, major: 6.6 (prolate); 3.7 (oblate) D2O DOSY 54
163 Micelle Minor: 3.25, major: 10.675   SAXS 147
163 Micelle (>0.6 mM) ∼123–190   DLS, NTA 154
163 Domain (100–0.1 μM) ∼70–190   DLS, NTA 154
163 Nanoassociate (10–1 nM) ∼160–195   DLS, NTA 154
164 Vesicle 25–125 pH 7.8 TEM, AFM, DLS 155
164 Vesicle ≤50 pH 7.8, sonicate 1 h AFM 155
164 Vesicle 25 pH 6.5 TEM 155
164 Vesicle 225 pH 8.5 TEM, DLS 155
164 Micelle 1.3 1 mM AgClO4 TEM 155
168 30–100 0.1 mM DLS, TEM 73
168 33–250 0.2 mM DLS, TEM 73
168 40–150; 250–350 0.6 mM DLS, TEM 73
168 50–350 0.8 mM DLS, TEM 73
168 55–400 1.0 mM DLS, TEM 73
168 35–55; 80–200 4.0 mM DLS, TEM 73
168 65–350 6.0 mM DLS, TEM 73
168 75–400 8.0 mM DLS, TEM 73
168 35–60; 150–250 10.0 mM DLS, TEM 73
170 Vesicle 60 ± 15 8 μM Cryo-TEM, DLS 173
170 Vesicle 50, 230 20 μM Cryo-TEM, DLS 173
171 Flattened bilayer 108 7.4 μM Cryo-TEM, DLS 173
171 Flattened bilayer 150 15 μM Cryo-TEM, DLS 173
175 Ellipsoidal micelle Minor: 1.40, major: 7.3 (prolate); 4.0 (oblate) D2O DOSY 54
184 Vesicle 150 ± 50 pH 4.5–12 SLS, DLS 156
184 Micelle 5 pH 3 SLS, DLS 156
185 Vesicle 150 ± 50 pH 4.5–12 SLS, DLS 156
185 Micelle 5 pH 3 SLS, DLS 156
192 SLN 130 PBS PCS 190
193 Mixture of micelles and large aggregates 12; 49; 133 Acetate pH 4.1 DLS, TEM 203
193 Mixture of micelles and large aggregates 8–10 Borate pH 8.6 DLS, TEM 203
196 Mixture of spherical micelles and large aggregates 9–10 HCl pH 1.2; phthalate pH 3; acetate pH 4.1 DLS, TEM 203
196 Mixture of spherical micelles and large aggregates 20–30 Borate pH 8.6 DLS, TEM 203
196 Mixture of spherical micelles, bilayers and cylindrical micelles PB pH 12 DLS, TEM 203
197 SLN 97   PCS 193
198 Mixture of tubular and ribbon-like aggregates 4–10 (radius), 8–100 (length) 1 mM Cryo-TEM 92
198 Fiber Liquid crystalline lamellar phase 30% THF aqueous Cryo-TEM 92
199   AFM 198
200   AFM 198
205 Vesicle 100–250 EtOH TEM, AFM 238
212 Vesicle 34, 125   DLS, TEM 202
212 Fiber 109 MeOH DLS, TEM 202
216 SLN 170 PBS PCS 190
217 SLN 177 PBS PCS 190
218 SLN 175 PBS PCS 190
219 SLN 74 Produced using THF PCS, AFM 225 and 226
219 SLN 74 Produced using EtOH PCS 226
219 SLN 98 Produced using acetone PCS 226
219 SLN 107 Produced using MeOH PCS 226
219 SLN 114 0.2 g L−1 PCS 226
219 SLN 132 0.3 g L−1 PCS 226
219 SLN 136 0.4 g L−1 PCS 226
219 SLN 130 0.5 g L−1 PCS 226
219 SLN 81 3% THF in production PCS 226
219 SLN 86 4% THF in production PCS 226
219 SLN 108 5% THF in production PCS 226
219 SLN 103 6% THF in production PCS 226
219 SLN 103 8% THF in production PCS 226
219 SLN 110 10% THF in production PCS 226
219 SLN 75 0.1 M NaCl PCS 226
219 SLN 80 0.1 M NaI PCS 226
219 SLN 83 0.1 M CH3CO2Na PCS 226
219 SLN 75 0.1 M NaHCO3 PCS 226
219 SLN 73 0.1 M KNO3 PCS 226
219 SLN 93 0.1 M KH2PO4 PCS 226
219 SLN 65   PCS 215
219 SLN 175 PBS PCS 190
219 SLN 75   PCS, AFM 193
219 SLN 69   PCS 225
219 SLN 70 Carbopol 980 aqueous PCS 225
219 SLN 73 Carbopol 2020 aqueous PCS 225
219 SLN 83 Hyaluronic acid aqueous PCS 225
219 SLN 76 Xanthane aqueous PCS 225
223 Vesicle 25–35, 100   TEM 233
223 Lamellar-like vesicle 25–500 MeOH TEM 233
223 Fiber CHCl3 TEM 233
223 Inverted micelle 13 Perfluorohexane TEM 233
223 Circular assembly 50 (radius), 25–30 (height)   AFM 257
224 SLN 74 0.1 M NaH2PO4 PCS 226
224 SLN 73 0.1 M KCl PCS 226
226 SLN 163 PBS PCS 190
227 SLN 92   PCS 193
231 140–200 0.8–7 mM, 10% DMF aqueous DLS 200
232 Micelle R g: 25.6 0.1 mM SAXS 205
232 Micelle R g: 30.5 0.5 mM SAXS 205
232 Micelle R g: 35.2 1.0 mM SAXS 205
232 Micelle 8–6 0.1–10 mM DLS 205
237 62–130 0.09–3 mM, 10% DMF aqueous DLS 200
238 14–8 0.25–16 mM DLS 200
239 Mixture of micelle-like aggregates and layers 4   DLS 227
240 8–4 0.15–16 mM DLS 200
241 9–5 0.15–16 mM DLS 200
242 15–5 0.25–20 mM DLS 200
247 Spherical particle R h: 107.1; Rg: 120.4   DLS, SLS, AFM 191
248 Spherical particle R h: 108.0; Rg: 120.3   DLS, SLS, AFM 191
249 Spherical particle R h: 98.6; Rg: 122.0   DLS, SLS, AFM 191
250 Spherical particle R h: 121.7; Rg: 135.0   DLS, SLS, AFM 191
251 Spherical particle R h: 106.8; Rg: 131.0   DLS, SLS, AFM 191
252 Spherical particle R h: 77.7; Rg: 91.0   DLS, SLS, AFM 191
255 14.3   DLS, TEM 213
256 5.5   DLS, TEM 213
257 79.5   DLS, TEM 213
258 10.3   DLS, TEM 213
259 34.7   DLS, TEM 213
260 17.7   DLS, TEM 213
261 Mixture of grape-like superstructures and nonlinear chains 60–85, 600–900 (length)   SEM, TEM 229
262 Mixture of micelles and large spherical aggregates 100–130; 350   DLS, SEM, TEM 229
278 Sheet-like monolayer 1.3   AFM, TEM 224
278 Bundles of sticks 1.4–16.6 (radius), 500–3500 (length) DMSO–H2O 1[thin space (1/6-em)]:[thin space (1/6-em)]9 AFM, TEM 224
278 Vesicle 25 Acetone–H2O 1[thin space (1/6-em)]:[thin space (1/6-em)]9 AFM, TEM 224
279 Linear or dot-like aggregate   AFM, TEM 224
279 Vesicle 25 DMSO–H2O 1[thin space (1/6-em)]:[thin space (1/6-em)]9 AFM, TEM 224
282 241 ± 30 3 mM DLS 232
282 240 ± 37 0.3 mM DLS 232
282 84 ± 4 30 μM DLS 232
282 131 ± 13 3 μM DLS 232
283 87 ± 11 3 mM DLS 232
283 227 ± 47 0.3 mM DLS 232
283 203 ± 15 30 μM DLS 232
283 415 ± 33 3 μM DLS 232
284 (Br) Particle 90.5 ± 11.5   DLS 237
284 (NO3) Particle 30.7 ± 8.4   DLS 235
284 (NO3) Particle 24 ± 3   DLS 236
286 Particle 7.3 ± 1.3   DLS 235
286 Particle 8 ± 1   DLS 236
287 Particle 1.9 ± 0.4   DLS 235
289 Spherical particle 70.8 5 mM Tris–HCl, pH 7.5, 1 mM (CA) DLS 247
289 Spherical particle 80.8 5 mM Tris–HCl, pH 7.5, 0.8 mM (CA) DLS 247
289 Spherical particle 104.5 5 mM Tris–HCl, pH 7.5, 0.1 mM (CA) DLS 247
289 Spherical particle 194.8 5 mM Tris–HCl, pH 7.5, 10 μM (CA) DLS 247
289 Spherical particle 244.4 5 mM Tris–HCl, pH 7.5, 1 μM (CA) DLS 247
290 Spherical particle 37.7 5 mM Tris–HCl, pH 7.5, 1 mM (CA) DLS 247
290 Spherical particle 72.8 5 mM Tris–HCl, pH 7.5, 0.8 mM (CA) DLS 247
290 Spherical particle 100.6 5 mM Tris–HCl, pH 7.5, 0.1 mM (CA) DLS 247
290 Spherical particle 122.4 5 mM Tris–HCl, pH 7.5, 10 μM (CA) DLS, TEM 247
290 Spherical particle 226.9 5 mM Tris–HCl, pH 7.5, 1 μM (CA) DLS 247
292 211 ± 37 0.3 mM DLS 250
292 168 ± 24 30 μM DLS 250
292 159 ± 102 3 μM DLS 250
292 99 ± 3 0.3 mM (CA), 0.3 mM Ag+ DLS 250
292 174 ± 61 30 μM (CA), 30 μM Ag+ DLS 250
292 218 ± 77 3 μM (CA), 3 μM Ag+ DLS 250
292 166 ± 12 0.3 mM (CA), 0.3 mM Ag+ DLS 250
292 265 ± 135 3 mM DLS 232
292 211 ± 37 0.3 mM DLS 232
292 168 ± 24 30 μM DLS 232
292 159 ± 102 3 μM DLS 232
293 378 ± 47 0.3 mM DLS 250
293 265 ± 135 30 μM DLS 250
293 118 ± 103 3 μM DLS 250
293 195 ± 42 30 μM (CA), 30 μM Ag+ DLS 250
293 189 ± 31 3 μM (CA), 3 μM Ag+ DLS 250
294 Micelle (17.0 ± 1.3)–(24.4 ± 1.4) 2–10 mM, D2O DOSY, AFM 252
294 Mixture of premicelles and large aggregates 100; 300 0.5 mM DOSY, DLS 254
294 Mixture of aggregate 50–100; 25   AFM 254
296 Homogeneous assembly 30–40 (radius), 3–5 (height)   AFM 257
305 Spherical particle 111.2 ± 17.4. PBS pH 7.4 DLS, TEM 259
311 Vesicle H2O–EtOH 1[thin space (1/6-em)]:[thin space (1/6-em)]3 TEM 242
325 Spherical particle 89.8 ± 14.8 PBS pH 7.4 DLS, TEM 259
370 100–110 0.33–10 g L−1 DLS 258
371 R h: 100–300; Rg: 70–140 0.8 mg L−1–1.2 g L−1 DLS 258
402 SLN 108   DLS 262
402 SLN 74 Produced using acetone DLS 262
402 SLN 215 Produced using EtOH DLS 262
402 SLN 106 0.2 g L−1 DLS 262
402 SLN 125 0.3 g L−1 DLS 262
402 SLN 123 0.4 g L−1 DLS 262
402 SLN 139 0.5 g L−1 DLS 262
402 SLN 117 5% glycerol DLS 262
402 SLN 99 10% glycerol DLS 262
402 SLN 114 15% glycerol DLS 262
402 SLN 102 20% glycerol DLS 262
402 SLN 104 25% glycerol DLS 262
403 SLN 72   DLS 262
404 SLN 70   DLS 262
405 SLN 50   DLS 262
406 SLN 41   DLS 262
407 R h: 4.242; Rg: 3.288 ± 0.044 0.5 mM DLS, SAXS 22
407 R h: 3.296; Rg: 2.555 ± 0.128 1 mM DLS, SAXS 22
407 R h: 34.06; Rg: 2.640 ± 0.014 5 mM DLS, SAXS 22
407 R h: 4.074; Rg: 3.158 ± 0.002 10 mM DLS, SAXS 22
407 5; 100   DLS 22
415 Particle 3 ± 0.2; 10 ± 1   DLS 236
420 Tube 15 (radius), 70–300 (length)   SEM 265
421 Tube 106 (radius), 108 (length)   SEM, AFM 265
422 Vesicle 370 ± 28 10 mM Tris, pH 7.4 DLS 268
422 Vesicle 158 ± 3 10 mM Tris, pH 7.4, 65 °C DLS 268
422 Vesicle 268 ± 13 10 mM Tris, pH 7.4, irradiated DLS 268
422 Vesicle 133 ± 5 10 mM Tris, pH 7.4, 65 °C, irradiated DLS 268
427 Vesicle 440 ± 40 10 mM Tris, pH 7.4 DLS 268
427 Vesicle 130 ± 10 10 mM Tris, pH 7.4, 65 °C DLS 268
427 Vesicle 245 ± 40 10 mM Tris, pH 7.4, irradiated DLS 268
427 Vesicle 120 ± 1 10 mM Tris, pH 7.4, 65 °C, irradiated DLS 268
428 150 ± 13 3 mM DLS 232
428 71 ± 16 0.3 mM DLS 232
428 136 ± 38 30 μM DLS 232
428 100 ± 19 3 μM DLS 232
429 SLN 66   DLS, SEM 120
430 Spherical particle 49.9 5 mM Tris–HCl, pH 7.5, 1 mM (CA) DLS 247
430 Spherical particle 52.2 5 mM Tris–HCl, pH 7.5, 0.8 mM (CA) DLS 247
430 Spherical particle 103.7 5 mM Tris–HCl, pH 7.5, 0.1 mM (CA) DLS 247
430 Spherical particle 119.8 5 mM Tris–HCl, pH 7.5, 10 μM (CA) DLS 247
430 Spherical particle 448.0 5 mM Tris–HCl, pH 7.5, 1 μM (CA) DLS 247
431 Spherical particle 46.4 5 mM Tris–HCl, pH 7.5, 1 mM (CA) DLS 247
431 Spherical particle 69.9 5 mM Tris–HCl, pH 7.5, 0.8 mM (CA) DLS 247
431 Spherical particle 212.9 5 mM Tris–HCl, pH 7.5, 0.1 mM (CA) DLS 247
431 Spherical particle 412.3 5 mM Tris–HCl, pH 7.5, 10 μM (CA) DLS 247
431 Spherical particle 502.0 5 mM Tris–HCl, pH 7.5, 1 μM (CA) DLS 247
432 62 ± 9 50 mM Tris, pH 7.4 DLS 266
433 66 ± 2 50 mM Tris, pH 7.4 DLS 266
434 62 ± 1 50 mM Tris, pH 7.4 DLS 266
443 Vesicle 42 ± 2 0.025 mM DLS 267
443 Vesicle 47 ± 1 0.05 mM DLS 267
443 Vesicle 53 ± 1 0.1 mM DLS 267
443 Vesicle 50 ± 2 0.25 mM DLS 267
443 Vesicle 42 ± 1 0.5 mM DLS 267
443 Vesicle 64 ± 2 0.75 mM DLS 267
443 Vesicle 62 ± 2 1.0 mM DLS 267
444 Vesicle 31 ± 1 0.01 mM DLS 267
444 Vesicle 24 ± 1 0.025 mM DLS 267
444 Vesicle 26 ± 1 0.05 mM DLS 267
444 Vesicle 25 ± 1 0.1 mM DLS 267
444 Vesicle 24 ± 1 0.25 mM DLS 267
444 Vesicle 25 ± 1 0.5 mM DLS 267
444 Vesicle 31 ± 1 0.75 mM DLS 267
444 Vesicle 31 ± 1 1.0 mM DLS 267
448 Vesicle 40 H2O–EtOH 1[thin space (1/6-em)]:[thin space (1/6-em)]2 TEM, SEM, AFM, DLS 273
449 Vesicle 70 H2O–EtOH 1[thin space (1/6-em)]:[thin space (1/6-em)]1 TEM, SEM, AFM, DLS 273
449 Vesicle 46 H2O–EtOH 3[thin space (1/6-em)]:[thin space (1/6-em)]1 TEM, SEM, AFM, DLS 273
450 Spherical aggregate 60–90 H2O–EtOH 1[thin space (1/6-em)]:[thin space (1/6-em)]1 TEM, SEM, AFM, DLS 273
450 Tubular aggregate 28 (radius) H2O–EtOH 3[thin space (1/6-em)]:[thin space (1/6-em)]1 TEM, SEM, AFM, DLS 273
451 Spherical aggregate 60–90 H2O–EtOH 1[thin space (1/6-em)]:[thin space (1/6-em)]1 TEM, SEM, AFM, DLS 273
451 Tubular aggregate 28 (radius) H2O–EtOH 3[thin space (1/6-em)]:[thin space (1/6-em)]1 TEM, SEM, AFM, DLS 273
452 Vesicle 145 H2O–EtOH 1[thin space (1/6-em)]:[thin space (1/6-em)]3 TEM, AFM, DLS 242
452 Mixture of vesicles and fibers H2O–EtOH 2[thin space (1/6-em)]:[thin space (1/6-em)]3 SEM, TEM 242
452 Fiber 50–100 (radius), 104 (length) H2O–EtOH 1[thin space (1/6-em)]:[thin space (1/6-em)]1 TEM, SEM, AFM 242
452 Nanotube 30–40 0.5 g L−1 HAuCl4, H2O–EtOH 2[thin space (1/6-em)]:[thin space (1/6-em)]1 TEM 275
452 Nanotube 0.5 g L−1 AgNO3, H2O–EtOH 2[thin space (1/6-em)]:[thin space (1/6-em)]1 TEM 275
453 Tubular aggregate H2O–EtOH 3[thin space (1/6-em)]:[thin space (1/6-em)]1 TEM, SEM, AFM, DLS 273


Compared with corresponding conventional surfactants, self-assemblies of amphiphilic calixarenes show diverse morphologies. For example, sodium dodecyl sulphate (SDS) forms spherical micelles with an average radius of 2.09 nm.280 Its corresponding calixarene, amphiphilic sulfonatocalix[4]arene 9, forms micelles with an average radius of 6.9 nm109 and the hexameric derivative 163 forms aggregates with various sizes (radii from about 70 nm to 195 nm) depending on the concentration.154 For positively charged surfactants, dodecylguanidine hydrochloride forms micelles as well,281 while the amphiphilic guanidinium-modified calix[4]arene 51 is able to form SLN with an average radius of 73 nm.117 Such great differences mainly come from their unique skeletons. It is well known that the critical packing parameter (CPP) proposed by Israelachivili and coworkers is a parameter to estimate the morphology of an amphiphilic assembly.282 Definition of the CPP value is P = VH/(a0lc), where VH is the volume occupied by hydrophobic groups in the assembly core, a0 is cross-sectional area occupied by the hydrophilic group at the assembly–solution interface, and lc is the chain length of the hydrophobic group in the assembly core. However, the CPP is hard to precisely apply in the case of macrocyclic amphiphiles. Various sizes and conformations of skeletons result in complicated, unpredictable, and diverse morphologies.

For example, Zhao and coworkers reported fully carboxylic acid modified amphiphilic calix[6]arene 305 and calix[8]arene 325.259 The mean radius of aggregates of 305 (111.2 ± 17.4 nm) is larger than that of 325 (89.8 ± 14.8 nm). Similarly, Xu and coworkers investigated choline modified amphiphilic calix[4]arene 62 and calix[5]arene 158.46 Despite their similar CAC values, the average radius of vesicles of 62 (75 nm) is almost two fold that of 158 (40 nm) (Fig. 2). The explanation of decreasing diameter with a larger skeleton is controversial; it may be related to an enhanced hydrophobic effect, different symmetry, or lower entropy loss. Exceptionally, Basilio and coworkers reported that an ellipsoidal micelle of amphiphilic sulfonatocalix[8]arene 175 has a longer main semiaxis (7.3 nm) than that of calix[6]arene 162 (6.6 nm), which is the result of a more flexible conformation of calix[8]arene.54


image file: c9qm00489k-f2.tif
Fig. 2 AFM images of (a) 278 and (b) 279 in pure water. Reprinted with permission from ref. 224. Copyright 2012 from Science China Press and Springer-Verlag Berlin Heidelberg. AFM images of (c) 94 and (d) 97 in 50 mM NaCl, pH 3. Reprinted with permission from ref. 122. Copyright 2012 from American Chemical Society. DLS data of (e) 62 and (f) 158 in water. Reprinted with permission from ref. 46. Copyright 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. (g) Schematic representation for morphology transitions in self-assembly of 449 and 451 with changes in medium polarity. Reprinted with permission from ref. 273. Copyright 2011 from Royal Society of Chemistry.

Conformation is also an important factor. Stoikov's group reported a series of quaternary ammonium-modified amphiphilic calix[4]arenes which have the same decoration and different conformations (283, 289 and 290 in cone conformation and 428, 430 and 431 in 1,3-alternate conformation).232,247 At a concentration of 0.3 mM, the radius of assembly of 283 (227 nm) is larger than that of 428 (71 nm). At a concentration of 1 mM, the radius of assembly of 289 (70.8 nm) is larger than that of 430 (49.9 nm) while the radius of assembly of 290 (37.7 nm) is smaller than that of 431 (46.4 nm). We assume that conformations of skeletons in assemblies affect the curvature and sizes of assemblies due to different aggregation modes.

Certainly, the length of hydrophobic chains and the structure of hydrophilic head groups could affect the morphologies of aggregates. For instance, increasing the hydrophobic chain from 6 carbons to 9 carbons causes different morphologies of amphiphilic aminocalix[4]arenes 94 and 97 assemblies, which are micelle and cylinder respectively (Fig. 2).122 For a series of amphiphilic calixarenes that show similar aggregation morphologies, some of them present a trend in size. Jebors and coworkers reported several SLNs assembled by acylcalix[9]arenes with different lengths of the carbon chain (402–406). The sizes of their aggregates decrease with increasing carbon atoms (radii decrease from 108 nm to 41 nm).262 Similarly, Burilov and coworkers studied two kinds of amine modified amphiphilic calixarenes with 4 carbons (98 and 105) and 8 carbons (99 and 106) as the hydrophobic chain, respectively.13698 and 99 are completely modified whereas 105 and 106 are partially modified. Aggregates of 98 and 105 show larger radii (88 nm and 97 nm, respectively) than those of 99 and 106 (70 nm and 77 nm, respectively), respectively. In principle, more and longer hydrophobic chains lead to a stronger hydrophobic effect, resulting in more compact packing, which leads to smaller aggregates. However, there are contrary examples such as a series of cyclodextrin modified amphiphilic calixarenes 127 and 128, whose aggregate size increases with increasing carbon chain (radii increase from 65 nm to 95 nm).163,164 This phenomenon may be related to the large volume of cyclodextrin. Besides, the aggregates of bola-type amphiphilic calixarenes 432–434 are of the same size, although they bear 4-carbon chains, 8-carbon chains, and 14-carbon chains, respectively.266 In brief, we just find limited examples of hydrophobic chains affecting the morphology with a certain trend, while in many cases, morphologies vary irregularly with chain length.

Hydrophilic head affecting the aggregation morphology is an even more complicated topic. Factors such as volume, hydration energy, and interactions between hydrophilic head groups may give us a clue, but it is still difficult to predict aggregate morphologies from their structure. Here we just name several examples that may provide some ideas. Stoikov and coworkers235–237,247 synthesized several amphiphilic butylthiacalix[4]arenes with quaternary ammonium, as well as amide (289, 290), ester (287), benzene (284), or phthalimide (286) as hydrophilic groups. The 287 assembly has a significantly smaller radius (1.9 nm) than those of 284 (30.7 nm), 286 (7.3 nm), 289 (>70.8 nm, Tris buffer) and 290 (>37.7 nm, Tris buffer), owing to the small size of the ester. Similar results were reported by Shahgaldian and coworkers on diethylphosphate and phosphate modified calixarene, 192 (130 nm) and 226 (163 nm), respectively.190 On the other hand, Li and coworkers reported cyclodextrin modified calixarene 279 and 278, which possess one and two β-cyclodextrins respectively.224 In pure water, 279 forms small linear or dot like assemblies, whereas 278 shows large sheet like aggregations (Fig. 2). This phenomenon could be explained by hydrogen bonds between cyclodextrins. Besides, Klymchenko's group synthesized amphiphilic calixarenes modified by choline (66) and a N-(2-aminoethyl)-N,N-dimethylammonium group (72).76,77 DLS results showed the micelles of 72 (3.04 nm) are little larger than those of 66 (2.82 nm), probably due to the larger hydration shell of amino groups as compared to hydroxyls. However, there are some examples showing that the morphology is not significantly influenced by different hydrophilic head groups. For example, Burilov and coworkers compared assembly behavior of amphiphilic thiacalix[4]arenes bearing carboxyl (427) and sulfonic (422) groups, respectively; these two compounds show similar shape and size.268 Compounds 212, 196, and 193, reported by Martin and coworkers, which possess amine, aminodiacetate, and phosphate groups, respectively, present similar results.202,203

The morphologies of assemblies are largely related to experimental conditions283 such as concentration. For example, Padnya and coworkers reported a series of quaternary ammonium based thiacalix[4]arenes 289 and 290, whose aggregate sizes increase with decreasing concentration (radii increase from 70.8 nm to 244.4 nm and from 37.7 nm to 226.9 nm, respectively, with concentration decrease from 1 mM to 1 μM).247 The authors assume that this phenomenon can be explained by the existence of two kinds of aggregates, spherical aggregates and elongated self-associates.

On the other hand, properties of solvents may modulate the morphology of amphiphilic calixarene assemblies, mainly by influencing the interactions of hydrophilic head groups. For instance, the polarity of solvent affects hydrogen bonds, resulting in a change in the packing mode of some amphiphiles. Liang and coworkers synthesized amphiphilic calix[6]biscrowns 450 and 451 possessing amide groups, interacting with each other via hydrogen bonds, at the hydrophilic part.273 Their morphologies underwent a clear transition from spherical to tubular aggregates when the solvent polarity, i.e. content of water in water/ethanol solution, is increased (Fig. 2), whereas analogues 448 and 449, without any amide linkage, only showed a size decrease upon the same change in solvent polarity. Similarly, two cyclodextrin modified amphiphilic calix[4]arenes 278 and 279,224 which we have already mentioned before, also present different assembly patterns in different solvents. With decreasing polarity, the morphology of 279 transferred from dots to linear aggregates and then to vesicles; meanwhile, 278 changed from sheet-like to bundle-like aggregations. All these examples show that lower solvent polarity enhances hydrogen bonds between head groups, resulting in larger aggregates.

pH of the solution is a common factor to modulate assembly morphology, by influencing electrostatic interactions and hydrophobicity. For groups whose pKa values are in a regular range, such as amine, carboxyl acid, and pyridine, adjusting the pH could change the number of charges they possess. More like charges at the hydrophilic head cause stronger repulsion, resulting in a larger curvature. For example, Martin and coworkers reported a phosphate modified amphiphilic calix[4]arene 196, whose major assembly morphology is bilayer at pH 4.1 while small micelles at pH 12.203 On the other hand, Houmadi and coworkers reported a sulfonatocalix[6]arene 164 with imidazolyl groups at the upper rim.155 At pH 6.5, the average radius of its assembly is 25 nm, which is much smaller than those at pH 7.8 (25–125 nm) and pH 8.5 (225 nm). This phenomenon could be explained by protonation of imidazolyl group affecting the hydrophilic and hydrophobic balance.

Salt concentration influencing assembly is another interesting topic, and it is also related to further application in biological systems. Houel and coworkers did a systematic study on salt concentration affecting assembly using phosphonate-modified calix[4]arenes 12 and 13.126 In the presence of monovalent cations (Na+, K+), no apparent change in size was observed over a concentration range from 0.1 mM to 145 mM. In contrast, divalent cations could cause a significant size increase as the concentration is increased from 2 mM. The authors assumed that divalent cations have the ability to crosslink the assemblies.

2.2.3 Uniform assembly. Constructing precisely defined aggregates not only represents an enormous interest and challenge for fundamental research, but also has been widely used in fields such as pharmaceuticals, catalysts, sensors, film precursors, and information storage. As reported by Cui and coworkers, monodisperse nanoparticles with a size variation of less than 5% show unique properties and higher performances as compared with the corresponding polydisperse nanoparticles.284 The major advantage of monodisperse particles may be attributed to the uniform properties of individual particles, which makes the property of whole particles strictly controllable.285 However, most of the common surfactants self-assemble into polydisperse assemblies. Thus, lots of effort has been dedicated to developing reliable preparation methods such as freeze–thaw and extrusion; however, a tedious operating procedure is needed. An alternative is appropriate design of amphiphilic building blocks, since the information determining their specific supramolecular assembly architecture must be encoded in their molecular structure. Fortunately, amphiphilic calixarenes are promising candidates due to their unique assembly properties. Many aggregations based on calixarenes presented fantastic monodispersed92,93,111,142,191,202,226,252,259,262,277 and unique aggregation numbers (Naggs). The reported Naggs are listed in Table 6.
Table 6 N aggs of amphiphilic calixarene assemblies
Compound N agg Conditiona Methodb Ref.
a The condition is 25 °C in pure water if no label. b AUC: analytical ultracentrifugation. AF4-MALS: multiangle light scattering coupled with asymmetric field flow fractionation.
4 4 10 mM NaCl SAXS, AF4-MALS, AUC 64 and 65
4 6 15 mM NaCl SAXS, AF4-MALS, AUC 65
6 17 10 mM NaCl SAXS, AF4-MALS, AUC 64
7 24 10 mM NaCl SAXS, AF4-MALS, AUC 64
46 12 pH 7 Cryo-TEM 91
47 7 27 mM Na+ and K+ Cryo-TEM 97
75 8 50 mM NaCl SAXS, AF4-MALS, AUC 63
76 8 50 mM NaCl SAXS, AF4-MALS, AUC 63
77 12 50 mM NaCl SAXS, AF4-MALS, AUC 63
77 12 100 mM NaCl SAXS 63
77 20 200–300 mM NaCl SAXS 63
78 12 50 mM NaCl SAXS, AF4-MALS, AUC 63
79 20 50 mM NaCl SAXS, AF4-MALS, AUC 63
91 6 50 mM NaCl, pH 3.0 SAXS, AF4-MALS, AUC 122 and 124
92 12 50 mM NaCl, pH 3.0 SAXS, AF4-MALS, AUC 124
93 12 50 mM NaCl, pH 3.0 SAXS, AF4-MALS, AUC 124
94 12 50 mM NaCl, pH 3.0 SAXS, AF4-MALS, AUC 122 and 124
100 12 50 mM NaCl, pH 3.0 SAXS, AFM, DLS 139
101 6 pH 3.2 SAXS, AF4-MALS 63
101 12 pH 10 SAXS, AF4-MALS 63
101 6 50 mM NaCl, pH 3.0 SAXS, FFF-MALS 140
101 12 50 mM NaCl, pH 10 SAXS, FFF-MALS 140
102 8 50 mM NaCl SAXS, AF4-MALS 63
125 24 50 mM NaCl, pH 7.0, 40 °C SAXS, AF4-MALS, AUC 157
125 20 50 mM NaCl, pH 12 SAXS, AF4-MALS, AUC 157
125 21 50 mM NaCl, pH 12, 40 °C SAXS, AF4-MALS, AUC 157
143 20 50 mM NaCl SAXS, AF4-MALS 63
143 12 50 mM NaCl SAXS, FFF-MALS 150
144 8 50 mM NaCl SAXS, FFF-MALS 150
145 3–4 50 mM NaCl SAXS, FFF-MALS 150
146 12 50 mM NaCl SAXS, AF4-MALS 63
147 3.6 50 mM NaCl AF4-MALS 63


In 2004, Kellermann and coworkers reported the first completely uniform and structurally precise micelle, whose structure was determined by cryo-TEM and 3D reconstruction techniques.97 The micelle is formed spontaneously by exactly seven 47 molecules (Fig. 3), which is a T-shaped compound and with third generation dendritic heads. Later, they reported another uniform micelle formed by twelve 46 molecules, which is with second generation dendritic heads.91 Compared with molecule 47, the smaller space required by 46 allows denser packing, resulting in a larger Nagg value.


image file: c9qm00489k-f3.tif
Fig. 3 A structurally precise micelle formed by exactly seven 47 molecules is determined by 3D reconstruction techniques. Reprinted with permission from ref. 97. Copyright 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Sakurai group systematically studied assembly behavior of a series of calixarene micelles, whose head groups, including sulfonate group,64,65 primary amine group,63,122,124 quaternary amine group,63 cysteine,139 glutamic acid,140 polyamidoamine,63 mono/disaccharides,63,157 PEG,63,150 and so on, were conjugated with calixarene at the upper rim by a click reaction. Using methods including SAXS, AUC, AF4-MALS and LS, the morphologies and Nagg values of these micelles were determined. They found that these Nagg values coincide with the vertex numbers of regular polyhedral structures when Nagg are less than 30, so they named these small micelles as platonic micelles since the regular polyhedral structures are called platonic solids. They proposed that the formation of platonic micelles is a result of the maximal coverage ratio, which means the ratio of the total area of the caps to the surface area of the sphere (Fig. 4).


image file: c9qm00489k-f4.tif
Fig. 4 Chemical structure of a calix[4]arene-based amphiphile and the schematic illustration of the effect of the size of interfacial area on the Nagg of the micelles composed of the amphiphiles. Reprinted with permission from ref. 65. Copyright 2018 from Royal Society of Chemistry.

It is clear that the equilibrium interfacial area between the hydrophilic and hydrophobic domains (a0) has a significant effect on the Nagg, which was proved by studying a series of amphiphilic calixarenes bearing PEGs with different molecular weights as hygrophilic head groups.150 Experiment results showed that amphiphile containing PEG of 550 g mol−1 forms a dodecamer while that of 1000 g mol−1 forms an octamer, since the former one has smaller a0. Both of the micelles are monodispersed; meanwhile, high molecular weight PEG (2000 g mol−1) leads to polydisperse micelles, because PEG 2000 exhibits a greater affinity for water and higher mobility than PEG 550 and 1000, resulting in a too large a0 to form stable monodisperse micelles.

The a0 value could be easily influenced by the solvent environment. As an example, high salt concentration decreases repulsion among head groups, resulting in smaller a0, thus leading to larger Nagg.63,65 Also, for head groups containing an amine or carboxyl group, pH variation may protonate or deprotonate them, resulting in a change in repulsion interaction among these head groups. Consequently, the a0 value increases with larger repulsion and vice versa, leading to different Nagg, or even a transition of morphology. For instance, amino-modified compounds 87 and 88 form spheres at pH 3.0 while form cylinders at higher pH.122

A more complicated example is the glutamic acid containing 100,140 since it allows a continuous change in the state of its head groups from cationic to zwitterionic and then to anionic with increasing pH, resulting in a morphological transformation from spherical to cylindrical and again to spherical. Their Naggs at pH 3.0 and 10 were determined as 6 and 12 respectively. The molecular modeling results showed that the glutamic acid moieties exhibited folded-back structures with deprotonated carboxylic acid, resulting in a smaller hydrophilic volume than that with the protonated amino groups, causing increased Nagg from pH 3.0 to pH 10. It is also noteworthy that its lc could also change during pH variation, because anions at pH 10 are more far away from the center of the molecule than cations at pH 3.0.

The ionized state change induced by pH change could also influence the hydrogen bond formation. Disaccharides containing 120 provides an interesting example.157 The micellar morphologies are cylindrical at pH 7.0 and micelles with Nagg of 20 at pH 12 (25 °C), due to the cleavage of the hydrogen bonds by deprotonation of the hydroxyl groups in the sugar molecules. Similarly, temperature also affects hydrogen bonds. As a result, compound 120 forms micelles with Nagg of 24 at 40 °C (pH 7), and forms micelles with Nagg of 12 at 40 °C (pH 12).

As we mentioned before, lc is also important to the Nagg of aggregates. According to packing parameter theory, Nagg is proportional to lc2, whose trend is consistent with experimental results of a series of quaternary amine group bearing calixarenes.63 As the number of carbons in the alkyl chain increases from 3 to 7, Nagg increases discretely from 8 to 12, and then to 20. However, a series of amine group bearing calixarenes show a different behavior.124 Their platonic micelles bearing butyl, heptyl, and hexyl chains remain at 12-mer. This phenomenon and discrete Nagg may indicate that the coverage ratio defined by the Tammes problem is more suitable than packing parameter theory in the case of investigating small micelles.

To test the universality of the platonic micelles, Sakurai's group also studied assembly behavior of a series of amphiphilic SC4As 4, 6–8.64,65Naggs of these micelles increase from 4 to 17 to 24 and then to cylindrical structures with increasing alkyl chain length from pentyl to hexyl to heptyl and then to octyl, respectively. Although the values of 17 and 24 do not agree with the vertex numbers of regular polyhedra, but they match the local maxima in the Thomson problem considering the Coulomb potential for the calculation of the best packing on a sphere with multiple identical spherical caps.

2.2.4 Compact packing. Compactness of assemblies is another crucial factor for the performances of various applications, for example, construction of a reliable drug delivery system180 or an efficient light harvesting material.46 However, compared with CAC and morphology, such a significant assembly property did not attract much attention, and there is no unified definition of compactness up to now. In general, the microviscosity of assemblies presents their compactness, which could be measured by fluorescence polarization (P). The shape of the IR or NMR peak reflects the environment surrounding a bond or nucleus, and is also used as a measure of compactness.

Due to their preorganized structures, amphiphilic calixarene assemblies show different compactness from that of the corresponding monomers. Shinkai and co-workers investigated the microviscosity of a series of amphiphilic calixarenes above their CACs by measuring P.49P values of a series of sulfonic group modified amphiphilic calixarenes 162, 299, 300, and 322 (0.033–0.106) are higher than those of SDS (0.020) and hexadecyltrimethylammonium chloride (0.016), which means more compact packing of calixarene micelles than conventional surfactant micelles.

Cho and co-workers reported that alanine-modified calix[4]arene 25 self-assembles into a hollow necklace-like structure at neutral pH.23 IR spectra showed strong hydrogen bonding between the carbonyl groups and the highly organized, closely packed hydrocarbon chains exhibiting sharp IR bands.

As an assembly property, compactness is also influenced by pH and salt concentration, which modulate head group interactions. For example, Becherer and co-workers reported that carboxylic group modified calix[4]arene 46 micelles are clearly smaller at pH 9 than those at neutral pH, which can be concluded that denser packing of the micelles occurs under basic conditions in comparison with the aggregates obtained at neutral pH.91 The required smaller space of head groups allows denser packing.

Xu and co-workers demonstrated choline-modified calixarene (62 and 158) based molecular light-harvesting platforms, whose spectrum tunability is affected by assembly compactness.46 When they increased the ionic strength of solvent, the ionic heads packed closer resulted in more compact aggregation, which led to higher energy-transfer efficiency and acceptor emission.

Although there have been only limited examples related to the compactness until now, we believe more and more systematic investigations will come up soon, since it is necessary for developing materials with better performance and reliability.

2.2.5 Slow kinetics. All four properties we mentioned above are related to thermodynamics, while kinetics, which is an interesting fundamental research topic as well as important basis of material preparation, is also essential. Due to the development of instruments and characterization methods, such as 2D exchange spectroscopy (2D EXSY), stop-flow, and time-resolved spectroscopy, kinetics of amphiphilic aggregation was investigated in detail. Originating from their multivalent feature, some amphiphilic calixarenes meet the higher energy barrier of assembly–bulky water exchange compared to conventional amphiphiles, resulting in slower kinetics.

As Basilio and co-workers reported, in contrast to conventional surfactants, the exchange rate of amphiphilic SC4A 6 between solution and micelle is slow on the NMR time scale.84 The rate constants were determined by 2D EXSY experiments and these constants were found to be several orders of magnitude lower than those of conventional surfactants and comparable to those of other amphiphilic calixarenes and gemini surfactants. The explanation for this result presumably lies in the fact that the sole barrier felt by the amphiphile entering the micelle arises from long-range electrostatic repulsions due to the micellar charge. As 6 is a preorganized surfactant with four negative charges at the upper rim, this could increase the activation barrier and consequently slow down the rate constant for the association.

Takahashi and co-workers observed that quaternary ammonium modified 77 micelles transit from a dodecamer to an icosamer induced by a rapid increase in the NaCl concentration (cNaCl), using a stopped-flow device and time-resolved SAXS.133 The Nagg remained at 12 during the first 60 s after the increase in cNaCl, and then abruptly increased to 20 (Fig. 5). They speculated that the following kinetic process might take place: (1) the micelles with Nagg = 12 become metastable after the cNaCl increases to 290 mM. (2) Within the micelles, fluctuation of 77 takes place, providing sufficient space for the insertion of other 77 molecules in a process that might be very slow. (3) Once one 77 has been inserted into the metastable micelle, Nagg rapidly increases to 20.


image file: c9qm00489k-f5.tif
Fig. 5 Time evolution of Nagg (blue circles) and the radius of gyration 〈S2z1/2 (red triangles). The solid curve for Nagg represents the fitted model curve. Reprinted with permission from ref. 133. Copyright 2017 from Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Similar examples of amphiphilic calixarenes forming meta-stable “kinetic trap” states were reported, with more diverse morphologies.286 For example, Strobel and co-workers reported that carboxylatocalix[4]arene 24 self-assembles into vesicles and long thin features that could possibly be rod-like micelles in dilute solution according to light scattering and cryo-TEM experiments.42 Houmadi and co-workers reported that 164 self-assembles into vesicles in freshly prepared solution.155 Vesicles of similar size and shape but with larger membrane shells were observed by TEM in 1 day old solutions, whereas giant vesicles appear after 1 week.

Despite scant examples, we have enough reason to predict a prosperous development of amphiphilic calixarene assembly kinetics. In general, highly kinetic systems at or close to equilibrium show uniform aggregate shapes and sizes, whereas systems with slow kinetics exhibit rather broad shape and size distributions.42 Consequently, kinetics is critical for preparation procedures of amphiphilic calixarene assemblies. The tailored preparation process is needed for fabricating well-designed assemblies according to their kinetics features. Moreover, the slow assembling kinetics of amphiphilic calixarenes can be applied in extensive fields, such as controlled release in drug delivery systems and dissipative self-assembly systems.

3. Calixarene-based supra-amphiphiles

Amphiphilic macrocycles possess cavities, which endow them with binding affinity to various guests. Taking this advantage, guests could modulate the aggregation behavior of amphiphilic macrocycles. By host–guest interactions as well, non-amphiphilic macrocycles own the ability to influence the aggregate properties of some surfactants. The concept of “supra-amphiphiles” proposed by Zhang and co-workers covers those behaviors, describing amphiphiles constructed on the basis of non-covalent interactions or dynamic covalent bonds.10,287–292

Specific to water soluble calixarenes, they interact with guests including dyes, drugs, and biomacromolecules by hydrophobic interactions, π–π interactions, electrostatic interactions and so on. Furthermore, their unique skeletons provide multivalent interaction sites. As a result, these guests efficiently affect the aggregation of amphiphilic calixarenes, and the aggregation behavior of these guests could be modulated by calixarenes conveniently. Based on the amphiphilicity of the host and guest molecules, the assembling features of calixarene-based supra-amphiphiles can be divided into guest-induced aggregation of host, host-induced aggregation of guest and mutual inducement (Scheme 5).


image file: c9qm00489k-s5.tif
Scheme 5 Schematic illustration of various types of calixarene-based supra-amphiphiles.

Chemical structures of host and guest molecules which have been used to construct supra-amphiphiles are summarized in Schemes 6, 7 and Tables 7, 8.


image file: c9qm00489k-s6.tif
Scheme 6 Structures of hydrophilic host molecules which have been used to construct supra-amphiphiles.

image file: c9qm00489k-s7.tif
Scheme 7 Structures of guest molecules which have been used to construct supra-amphiphiles.
Table 7 References of host molecules which have been used to construct supra-amphiphiles in Scheme 6
Compound Ref. Compound Ref. Compound Ref.
454 293–308 457 293, 296 and 307 460 309
455 298, 309 and 310 458 311–315 461 316
456 293, 296 and 317–319 459 303 and 320 462 321


Table 8 References of guest molecules which have been used to construct supra-amphiphiles in Scheme 7
Compound Ref. Compound Ref. Compound Ref. Compound Ref.
G1 322 G14 305 G27 306 G40 252
G2 322 G15 302 G28 293 G41 317
G3 322 G16 320 G29 295 G42 307 and 317–319
G4 322 G17 300 G30 296 G43 317
G5 316 G18 300 G31 55 G44 310
G6 138 G19 300 G32 162 G45 88
G7 57 G20 304 G33 162 G46 161
G8 311 G21 298 G34 173 G47 161
G9 312 G22 303 G35 297 G48 301
G10 311–315 G23 308 G36 162 G49 161
G11 294 and 319 G24 319 G37 162 G50 266
G12 311 G25 319 G38 309 G51 211
G13 299 G26 319 G39 309


3.1 Guest-induced aggregation of host

3.1.1 Guest-decreased CAC. A series of typical host molecules whose aggregation could be induced by guests is amphiphilic SCnAs owing to their good water solubility and binding affinity (Table 9). The interaction with cationic guests reduces electrostatic repulsion between their sulfonic groups, resulting in a smaller CAC. For instance, Hu and coworkers reported the aggregation of amphiphilic calix[4]arene 3 induced by diquat (G31).55 In the absence of G31, the CAC value of 3 is 3.18 mM, while it decreases about 12 times (0.25 mM) in the presence of G31. Later, Fernandez-Abad and coworkers reported that DSMI (G7) could also decrease the CAC of 3 to 1.4 mM.57 Moreover, it is also reported that the CAC of analogue 6 decreases in the presence of G45.88
Table 9 Morphologies of guest-induced host assemblies and CACs of corresponding hosts
Host Guest Morphology Radius (nm) CAC Quantity (host[thin space (1/6-em)]:[thin space (1/6-em)]guest) Conditiona Method Ref.
a The condition is 25 °C in pure water if no label.
3 3.18 mM   55
3 G31 0.25 mM 1[thin space (1/6-em)]:[thin space (1/6-em)]1   Fluorescence 55
3 G7 1.4 mM 3 mM (guest)   Conductivity 57
6 Micelle 330 μM   Fluorescence 88
6 G45 Mult-lamellar sphere 81 35 μM 50 μM (guest)   DLS, TEM 88
62 Micelle 2.7 0.9 mM   ITC, DLS 138
62 G6 Vesicle 247 0.02 mM 1[thin space (1/6-em)]:[thin space (1/6-em)]1   UV-vis, DLS, SEM, TEM, AFM 138
111 Micelle 20–100 1.2 mM pH 3.0 CD, DLS, AFM, TEM, SEM 161
111 G46 Branched fiber 103–104 (length) 1[thin space (1/6-em)]:[thin space (1/6-em)]4 pH 3.0 AFM, TEM, SEM 161
111 G49 Twisted fiber 103–3 × 103 (length) 1[thin space (1/6-em)]:[thin space (1/6-em)]4 pH 3.0 AFM, TEM, SEM 161
111 G47 Network 1[thin space (1/6-em)]:[thin space (1/6-em)]4 pH 3.0 AFM, TEM, SEM 161
111 G32 Rod-like fiber 1[thin space (1/6-em)]:[thin space (1/6-em)]1 pH 3.0 AFM, SEM 162
111 G33 Rod-like fiber 1[thin space (1/6-em)]:[thin space (1/6-em)]1 pH 3.0 AFM, SEM 162
111 G36 Network 2 × 103–5 × 103 (length) 1[thin space (1/6-em)]:[thin space (1/6-em)]1 pH 3.0 AFM, SEM 162
111 G37 Network 1[thin space (1/6-em)]:[thin space (1/6-em)]1 pH 3.0 AFM, SEM 162
142 Mixture of micelles and NPs 2.5; 40 13 μM   DLS, HR TEM 322
142 G4 Mixture of hollow micelles and hollow rod-like micelles 6 1[thin space (1/6-em)]:[thin space (1/6-em)]1   DLS, HR TEM, cryo-TEM 322
142 G3 Mixture of micelles and NPs 5 1[thin space (1/6-em)]:[thin space (1/6-em)]1   DLS, HR TEM, cryo-TEM 322
143 G1 Hollow micelle 5–10 1[thin space (1/6-em)]:[thin space (1/6-em)]1   DLS, HR TEM, cryo-TEM 322
143 G2 Linear micelle 3.8 (radius), 50–400 (length) 1[thin space (1/6-em)]:[thin space (1/6-em)]1   DLS, HR TEM, cryo-TEM 322
170 Vesicle 60 ± 15 7.9 ± 0.5 μM   Fluorescence, DLS 173
170 G34 Mixture of micelles, vesicles and super-aggregates <10; >25; 50–100 7.2 ± 0.3 μM 1[thin space (1/6-em)]:[thin space (1/6-em)]1   Fluorescence, DLS, cryo-TEM, TEM 173
254 G51 Vesicle 40–155   10[thin space (1/6-em)]:[thin space (1/6-em)]1 Dioxane[thin space (1/6-em)]:[thin space (1/6-em)]water 5[thin space (1/6-em)]:[thin space (1/6-em)]1 TEM, DLS 211
254 G51 Vesicle 85   5[thin space (1/6-em)]:[thin space (1/6-em)]1 Dioxane[thin space (1/6-em)]:[thin space (1/6-em)]water 5[thin space (1/6-em)]:[thin space (1/6-em)]1 TEM, DLS 211
254 G51 Spherical micelle 65   1[thin space (1/6-em)]:[thin space (1/6-em)]1 Dioxane[thin space (1/6-em)]:[thin space (1/6-em)]water 5[thin space (1/6-em)]:[thin space (1/6-em)]1 TEM, DLS 211
254 G51 Micelle ∼150   1[thin space (1/6-em)]:[thin space (1/6-em)]5 Dioxane[thin space (1/6-em)]:[thin space (1/6-em)]water 5[thin space (1/6-em)]:[thin space (1/6-em)]1 TEM, DLS 211
254 G51 Mixture of network aggregates and spherical micelles ∼200   1[thin space (1/6-em)]:[thin space (1/6-em)]10 Dioxane[thin space (1/6-em)]:[thin space (1/6-em)]water 5[thin space (1/6-em)]:[thin space (1/6-em)]1 TEM, DLS 211
432 62 ± 9 91 ± 5 μM 50 mM Tris pH 7.4 Fluorescence 266
432 G50 45 ± 3 2.0 ± 0.1 μM 10[thin space (1/6-em)]:[thin space (1/6-em)]1 50 mM Tris pH 7.4 Fluorescence, DLS 266
433 66 ± 2 59 ± 3 μM 50 mM Tris pH 7.4 Fluorescence 266
433 G50 53 ± 2 2.6 ± 0.2 μM 10[thin space (1/6-em)]:[thin space (1/6-em)]1 50 mM Tris pH 7.4 Fluorescence, DLS 266
434 G50 58 ± 4 2.0 ± 0.1 μM 10[thin space (1/6-em)]:[thin space (1/6-em)]1 50 mM Tris pH 7.4 Fluorescence, DLS 266
434 62 ± 1 33 ± 2 μM 50 mM Tris pH 7.4 Fluorescence 266
294 Micelle 2.44 0.64 mM D2O DOSY, AFM 252
294 G40 Micelle 0.35 mM 1[thin space (1/6-em)]:[thin space (1/6-em)]1 D2O DOSY 252


Aggregation of calixarenes bearing sulfonic groups at the lower rim could also be induced by cationic guests. Gattuso and coworkers synthesized an amphiphilic calix[5]arene 294, and DOSY results showed that its CAC was 0.64 mM.252 In the presence of G40, its CAC decreases to 0.35 mM.251,252 The inclusion of guests into the cavity of 294 is clearly proved by DOSY results, while some guests involved in the assembly are located outside the cavity. It is noteworthy that the CAC values of guests also decrease upon addition of 294.

Following the same principle, anionic guest induced cationic calixarene aggregation was also reported by Wang and coworkers.138 The CAC value of a quaternary ammonium-modified calix[4]arene 59 decreases by 45 times in the presence of ATP (G6). Similarly, Burilov and coworkers synthesized several ammonium modified amphiphilic thiacalix[4]arenes (432–434) and studied their aggregation behavior in the absence and presence of Eosin Y (G50).266 CAC values of all these thiacalix[4]arenes, no matter the length of the hydrophobic chain, showed a significant decrease (at least 15 folds) with addition of G50.

3.1.2 Guest-regulated morphology. Besides decreasing CAC, guest promoted amphiphilic calixarene assembly also presents a transfer of morphology. Since the electrostatic repulsion is reduced by guests, the amphiphilic calixarenes tend to form larger aggregates.

For example, 6 forms small micelles in the absence of a guest, while forms aggregates with 81 nm average radius in the presence of G45, which was proved by DLS, TEM, and significant Tyndall effect.88 Similar results were reported in the study of 59 in the presence of G6 (Fig. 6).138


image file: c9qm00489k-f6.tif
Fig. 6 (a) Schematic illustration of gel generation from gelator 107 induced by basic amino acids. Reprinted with permission from ref. 161. Copyright 2011 from Royal Society of Chemistry. (b) Schematic illustration of the self-assembly of 59 with ATP (G6) and its phosphatase-response. Reprinted with permission from ref. 138. Copyright 2013 from Royal Society of Chemistry.

Moreover, guest induced larger aggregates could further form hydrogels. Liu's group reported several hydrogels constructed by proline modified calix[4]arene 107, in the presence of different guests.161,162107 itself forms spherical aggregates with a wide size dispersion. However, upon mixing with G32, G33, G36, G37, G46, G47, and G49, the morphology of 107 changed to fibers, resulting in a binary hydrogel. AFM, SEM, and TEM results showed that the fiber shapes differed with guests. For example, the fibers of the 107G46 are composed of long and branched fibers, while 107G49 are shorter and twisted. And a denser network with stacks of rod-like nanofibers was observed in 107G47 (Fig. 6).

3.2 Host-induced aggregation of guests

As we mentioned before, when a cationic surfactant G45 is used to promote aggregation of an anionic amphiphilic calixarene 6, the CAC value of G45 decreases as well. This mutually inducing phenomenon further provides us the idea that hydrophilic calixarenes should also have the ability to enhance aggregation of amphiphiles. In fact, calixarene-induced aggregation (CIA) was first reported in 2001,321 and has become more popular since 2009. The most typical hosts are SCnAs, which are capable of binding hundreds of guests with impressive affinity and promoting self-assembly of about 30 molecules in aqueous media. The concept of CIA was proposed in 2012, which means an appropriate concentration of SCnAs could lower some amphiphilic molecules’ CAC, enhance aggregate stability and compactness, and regulate the degree of order in the aggregates. This strategy could be applied to aromatic fluorescent dyes, surfactants, drugs, and biomacromolecules. Some of them have been summarized in previous reviews by García-Río16 and our group.3,323 Herein, instead of listing all the results in this field, we focus on the properties of CIA assembly with assistance of some typical works.

From the viewpoint of intermolecular interactions, the hydrophobic interaction is the main driving force of conventional surfactant micelle formation, while electrostatic repulsion of its head group is unfavorable for assembly. SCnAs possessing multivalent negative charges could lower the potential energy of electrostatic repulsion efficiently. As a result, in the presence of SCnAs, surfactants tend to show lower CAC, more regular arrangement, and more compact packing (Table 10).

Table 10 Morphologies of host-induced guest assemblies and CACs of corresponding guests
Host Guest Morphology Radius (nm) CAC Quantity (host[thin space (1/6-em)]:[thin space (1/6-em)]guest) Conditiona Method Ref.
a The condition is 25 °C in pure water if no label.
461 G5 Vesicle 150–300 74 μM 1[thin space (1/6-em)]:[thin space (1/6-em)]3 pH 6.8 Surface tension, DLS, TEM 316
461 G5 Vesicle 220–310 1[thin space (1/6-em)]:[thin space (1/6-em)]3 pH 4–11 DLS 316
G8 Micelle 340 μM   Surface tension 311
458 G8 Micelle 23 μM 1 mM (host)   Surface tension 311
G9 Micelle 310 mM   Surface tension 311
458 G9 Micelle 25 mM 1 mM (host)   Surface tension 311
G10 Micelle 0.9 14 mM   Surface tension, fluorescence, DLS 311
458 G10 Micelle 3.0 0.20 mM 5[thin space (1/6-em)]:[thin space (1/6-em)]1   Surface tension, fluorescence, DLS 311
458 G10 Micelle 3.3 0.20 mM 5[thin space (1/6-em)]:[thin space (1/6-em)]2   Surface tension, fluorescence, DLS 311
458 G10 Micelle 3.5 0.20 mM 1[thin space (1/6-em)]:[thin space (1/6-em)]1   Surface tension, fluorescence, DLS 311
458 G10 Micelle 6.1 0.20 mM 1[thin space (1/6-em)]:[thin space (1/6-em)]10   Surface tension, fluorescence, DLS 311
458 G10 Micelle 3.0 0.20 mM 1[thin space (1/6-em)]:[thin space (1/6-em)]20   Surface tension, fluorescence, DLS 311
458 G10 Micelle 1.6 0.20 mM 1[thin space (1/6-em)]:[thin space (1/6-em)]40   Surface tension, fluorescence, DLS 311
458 G10 Micelle 1.1 0.20 mM 1[thin space (1/6-em)]:[thin space (1/6-em)]80   Surface tension, fluorescence, DLS 311
454 G11 Vesicle, small NP 250–2500 50 mM, 1[thin space (1/6-em)]:[thin space (1/6-em)]2.5   Nomarski light microscopy 294
454 G11 Vesicle 57.2 ± 0.4 2 mM, 1[thin space (1/6-em)]:[thin space (1/6-em)]2.5   DLS, TEM 294
456 G11 Spherical and ellipsoid NP 46 1[thin space (1/6-em)]:[thin space (1/6-em)]6–7   DLS 319
456 G11 Supramolecular micelle 3.4 ± 0.3 1[thin space (1/6-em)]:[thin space (1/6-em)]4 15 mM NaCl, 10 °C DLS 319
456 G11 Supramolecular micelle 20 μM 1[thin space (1/6-em)]:[thin space (1/6-em)]2, 3 50 mM NaCl Fluorescence 319
G12 14 mM   Surface tension, conductivity 313
458 G12 Micelle 0.16 mM 0.1 mM (host)   Surface tension, conductivity 313
458 G12 Micelle 0.16 mM 0.5 mM (host)   Surface tension, conductivity 313
458 G12 0.3 mM 0.5 μM (host)   Surface tension 315
458 G12 0.4 mM 1 μM (host)   Surface tension 315
458 G12 20 mM 0.2 μM (host)   Fluorescence 315
458 G12 0.3 mM 2 μM (host)   Fluorescence 315
458 G12 0.2 mM 0.5 mM (host)   Fluorescence 315
G13 Micelle   2.5 mM   299
454 G13 16 μM 0.02 mM (host)   UV-vis 299
454 G13 31 μM 0.05 mM (host)   UV-vis 299
454 G13 31 μM 0.08 mM (host)   UV-vis 299
454 G13 Vesicle 97 1[thin space (1/6-em)]:[thin space (1/6-em)]10   UV-vis, DLS, TEM, SEM, cryo-TEM, HR TEM 299
G14 Micelle 4.3 ± 0.7 (162 ± 8) μM 35 °C Surface tension, NMR, light microscopy, cryo-TEM 305
454 G14 Micelle 30 ± 2 (93 ± 2) mM 1[thin space (1/6-em)]:[thin space (1/6-em)]250 35 °C Surface tension, NMR, light microscopy, cryo-TEM 305
454 G14 Micelle (13 ± 1) mM 1[thin space (1/6-em)]:[thin space (1/6-em)]100 35 °C Surface tension, NMR, light microscopy, cryo-TEM 305
454 G14 Micelle 29 ± 3 (6.5 ± 0.8) mM 1[thin space (1/6-em)]:[thin space (1/6-em)]70 35 °C Surface tension, NMR, light microscopy, cryo-TEM 305
454 G14 Mixture of bilayer-based tubules and vesicles 12 ± 1 1[thin space (1/6-em)]:[thin space (1/6-em)]25 35 °C Surface tension, NMR, light microscopy, cryo-TEM 305
454 G14 Mixture of bilayer-based tubules and vesicles 6.0 ± 0.2 1[thin space (1/6-em)]:[thin space (1/6-em)]15 35 °C Surface tension, NMR, light microscopy, cryo-TEM 305
G15 6.0 mM   Fluorescence, surface tension 302
454 G15 70 μM 20 μM (host)   Fluorescence, surface tension 302
454 G15 80 μM 50 μM (host)   Fluorescence, surface tension 302
454 G15 100 μM 80 μM (host)   Fluorescence, surface tension 302
454 G15 Spherical aggregate 196 4[thin space (1/6-em)]:[thin space (1/6-em)]15   DLS, TEM, SEM 302
459 G16 Platelet-like micelle 300 (length); 100 (width); 20 (height) 1.2[thin space (1/6-em)]:[thin space (1/6-em)]2 25 °C TEM, AFM 320
459 G16 Cross-linked NP 1.2[thin space (1/6-em)]:[thin space (1/6-em)]2 37 °C DLS, TEM 320
G17 1 mM   300
454 G17 2.5 μM 0.02 mM (host)   UV-vis 300
454 G17 5.3 μM 0.04 mM (host)   UV-vis 300
454 G17 7.3 μM 0.06 mM (host)   UV-vis 300
454 G17 Vesicle 66.2 2[thin space (1/6-em)]:[thin space (1/6-em)]5   DLS, TEM, SEM, AFM 300
G18 1 mM   300
454 G18 3.1 μM 0.02 mM (host)   UV-vis 300
454 G18 3.2 μM 0.04 mM (host)   UV-vis 300
454 G18 3.7 μM 0.06 mM (host)   UV-vis 300
454 G18 Vesicle 62.3 2[thin space (1/6-em)]:[thin space (1/6-em)]5   DLS, TEM, SEM, AFM 300
G19 1 mM   300
454 G19 3.7 μM 0.02 mM (host)   UV-vis 300
454 G19 5.0 μM 0.04 mM (host)   UV-vis 300
454 G19 6.6 μM 0.06 mM (host)   UV-vis 300
454 G19 Vesicle 49.0 2[thin space (1/6-em)]:[thin space (1/6-em)]5   DLS, TEM, SEM, AFM 300
G20 0.14 mM   Conductivity 304
454 G20 0.125 mM 50 μM (host)   UV-vis 304
454 G20 Multilamellar sphere R h: 141, Rg: 108 1[thin space (1/6-em)]:[thin space (1/6-em)]4   DLS, SLS, TEM 304
454 G21 Mixtures of fibers and something larger 96   DLS 298
454 G21 Mixture of fibers and columnar stacks 100   DLS, TEM, SEM, AFM 298
G22 Spherical aggregate 55 0.14 mM   Surface tension, DLS, TEM, AFM 303
454 G22 7.0 μM 1[thin space (1/6-em)]:[thin space (1/6-em)]2   Surface tension 303
454 G22 Multilamellar spherical aggregate 30 1[thin space (1/6-em)]:[thin space (1/6-em)]2   DLS, TEM, AFM 303
459 G22 Spherical and linear aggregate 60 1[thin space (1/6-em)]:[thin space (1/6-em)]4   DLS, TEM, AFM 303
G23 240 90 μM   DLS 308
454 G23 72 0.8 μM 1[thin space (1/6-em)]:[thin space (1/6-em)]1   DLS 308
456 G24 Spherical and oblate lamellar NP 15–48 1[thin space (1/6-em)]:[thin space (1/6-em)]2–7   DLS 319
456 G24 Supramolecular micelle 2.4 ± 0.2 1[thin space (1/6-em)]:[thin space (1/6-em)]3 50 mM NaCl, 15 °C DLS 319
456 G24 Supramolecular micelle 16 μM 1[thin space (1/6-em)]:[thin space (1/6-em)]2 50 mM NaCl Fluorescence 319
456 G25 Spherical lamellar NP 20–39 1[thin space (1/6-em)]:[thin space (1/6-em)]2–6   DLS 319
456 G26 Spherical NP 25–41 1[thin space (1/6-em)]:[thin space (1/6-em)]2–6   DLS 319
454 G27 0.078 mM 0.05 mM   UV-vis 306
454 G27 0.062 mM 0.02 mM   UV-vis 306
454 G27 0.103 mM 0.08 mM   UV-vis 306
454 G27 Spherical NP 133.36 2[thin space (1/6-em)]:[thin space (1/6-em)]5   DLS, TEM 306
G35 20 mM   297
454 G35 0.02 mM 0.02 mM (host)   UV-vis 297
454 G35 0.04 mM 0.05 mM (host)   UV-vis 297
454 G35 0.07 mM 0.08 mM (host)   UV-vis 297
454 G35 Vesicle 181 1[thin space (1/6-em)]:[thin space (1/6-em)]2   DLS, TEM, SEM 297
460 G38 Fiber-like 104 (length) 1[thin space (1/6-em)]:[thin space (1/6-em)]5 0.1 M PB, pH 7.2 AFM, SEM 309
460 G39 Flake-like 1.5–1.7 (height) 1[thin space (1/6-em)]:[thin space (1/6-em)]2 0.1 M PB, pH 7.2 AFM, SEM 309
455 G39 NP 0.8–0.9 1[thin space (1/6-em)]:[thin space (1/6-em)]1 0.1 M PB, pH 7.2 AFM 309
456 G41 NP 65 ± 10 1[thin space (1/6-em)]:[thin space (1/6-em)]2   DLS 317
456 G41 NP 88 ± 28 1[thin space (1/6-em)]:[thin space (1/6-em)]5   DLS 317
456 G41 NP 80–190 1[thin space (1/6-em)]:[thin space (1/6-em)]3–120   DLS 317
456 G42 NP 80 ± 30 1[thin space (1/6-em)]:[thin space (1/6-em)]1   DLS 317
456 G42 NP 75–150 1[thin space (1/6-em)]:[thin space (1/6-em)]1–200   DLS 317
456 G42 Lamellar spherical aggregate 65–100 1[thin space (1/6-em)]:[thin space (1/6-em)]2   DLS, cryo-TEM, SANS 317
456 G42 Multilayered spherical aggregate 35–75 1[thin space (1/6-em)]:[thin space (1/6-em)]20   DLS, cryo-TEM, SANS 317
G42 Micelle 2.3 ± 0.2 20 mM NaCl DLS 318
456 G42 NP 33–100 1[thin space (1/6-em)]:[thin space (1/6-em)]6 0–110 mM NaCl DLS 318
456 G42 NP 33–119 1[thin space (1/6-em)]:[thin space (1/6-em)]5 0–110 mM NaCl DLS 318
456 G42 NP 25–87 1[thin space (1/6-em)]:[thin space (1/6-em)]4 0–40 mM NaCl DLS 318
456 G42 Supramolecular micelle 3.0 ± 0.2 1[thin space (1/6-em)]:[thin space (1/6-em)]4 40–53 mM NaCl DLS 318
456 G42 NP 28–69 1[thin space (1/6-em)]:[thin space (1/6-em)]3 0–25 mM NaCl DLS 318
456 G42 Supramolecular micelle 3.0 ± 0.2 1[thin space (1/6-em)]:[thin space (1/6-em)]3 25–33 mM NaCl DLS 318
456 G42 NP 33–94 1[thin space (1/6-em)]:[thin space (1/6-em)]2 0–15 mM NaCl DLS 318
456 G42 Supramolecular micelle 3.0 ± 0.2 1[thin space (1/6-em)]:[thin space (1/6-em)]2 15–17 mM NaCl DLS 318
456 G42 Supramolecular micelle – NP 3–250 1[thin space (1/6-em)]:[thin space (1/6-em)]2 15 mM NaCl, 27–33 °C DLS 318
456 G42 Supramolecular micelle – NP 3–250 1[thin space (1/6-em)]:[thin space (1/6-em)]2 50 mM NaCl, 33–38 °C DLS 318
456 G42 NP 80 1[thin space (1/6-em)]:[thin space (1/6-em)]3 15 mM NaCl, 20 °C DLS 318
456 G42 Supramolecular micelle 3 1[thin space (1/6-em)]:[thin space (1/6-em)]3 15 mM NaCl, 25 °C DLS 318
456 G42 NP 185 1[thin space (1/6-em)]:[thin space (1/6-em)]3 15 mM NaCl, 30 °C DLS 318
456 G42 NP 36 ± 10 1[thin space (1/6-em)]:[thin space (1/6-em)]4   Cryo-TEM 318
456 G42 Supramolecular micelle <8 1[thin space (1/6-em)]:[thin space (1/6-em)]4 53 mM NaCl Cryo-TEM 318
G42 Micelle 720 μM 50 mM NaCl Fluorescence 318
456 G42 15 μM 1[thin space (1/6-em)]:[thin space (1/6-em)]2 50 mM NaCl Fluorescence 318
456 G42 15 μM 1[thin space (1/6-em)]:[thin space (1/6-em)]1 50 mM NaCl Fluorescence 318
456 G42 15 μM 1[thin space (1/6-em)]:[thin space (1/6-em)]3 50 mM NaCl Fluorescence 318
456 G42 15 μM 1[thin space (1/6-em)]:[thin space (1/6-em)]3.6 50 mM NaCl Fluorescence 318
454 G42 NP 100 1[thin space (1/6-em)]:[thin space (1/6-em)]2 0–0.08 mM NaCl DLS, cryo-TEM 307
454 G42 NP 100 1[thin space (1/6-em)]:[thin space (1/6-em)]4 0–0.07 mM NaCl DLS, cryo-TEM 307
457 G42 NP 23–45 1[thin space (1/6-em)]:[thin space (1/6-em)]2–9   DLS 307
457 G42 NP 45 1[thin space (1/6-em)]:[thin space (1/6-em)]6.8–8.8 0–50 mM NaCl DLS 307
457 G42 Supramolecular micelle – NP 2.5–350 1[thin space (1/6-em)]:[thin space (1/6-em)]4.9 30 mM NaCl, 45–55 °C DLS 307
457 G42 Supramolecular micelle – NP 2.5–320 1[thin space (1/6-em)]:[thin space (1/6-em)]4.9 50 mM NaCl, 50–55 °C DLS 307
457 G42 NP – supramolecular micelle 45–2.5 1[thin space (1/6-em)]:[thin space (1/6-em)]5.8 0–50 mM NaCl DLS 307
457 G42 NP – supramolecular micelle 38–2.5 1[thin space (1/6-em)]:[thin space (1/6-em)]3.9 0–50 mM NaCl DLS 307
457 G42 15 μM 1[thin space (1/6-em)]:[thin space (1/6-em)]2.0 50 mM NaCl Fluorescence 307
457 G42 12 μM 1[thin space (1/6-em)]:[thin space (1/6-em)]5.9 50 mM NaCl Fluorescence 307
456 G43 NP 55 ± 13 1[thin space (1/6-em)]:[thin space (1/6-em)]1   DLS 317
456 G43 NP 60–90 1[thin space (1/6-em)]:[thin space (1/6-em)]1–200   DLS 317
G44 0.27 mM   Fluorescence 310
455 G44 0.07 mM 0.02 mM (host)   Fluorescence 310
455 G44 0.09 mM 0.05 mM (host)   Fluorescence 310
455 G44 0.08 mM 0.08 mM (host)   Fluorescence 310
455 G44 Vesicle 49.4 1[thin space (1/6-em)]:[thin space (1/6-em)]4   DLS, TEM, SEM 310


3.2.1 Host-decreased CAC. A representative example of CIA is SC4A (454) inducing myristoylcholine (G13) aggregation. In this work, the CAC value of G13 decreased significantly by a factor of ca. 100 with addition of an appropriate amount of 454. Similar results were reported on various guests such as gemini surfactants G17G19,300 1-pyrenemethylaminium (G44),310 1-methyl-3-tetradecylimidazolium (G41),317 cationic serine-based surfactant G14305 and so on. In general, the CAC value depends on the ratio of guest and SCnA, and the appropriate ratio was often determined by transmittance measurements. If the SCnA concentration is much less than that of the surfactant, there is no enough opposite charges to reduce electrostatic repulsion efficiently. On the other hand, too much SCnA concentration provides excess cavities to include surfactants, resulting in disassembling. However, García-Río and coworkers reported that sulfonatocalix[6]arene hexamethyl ether (458) concentration hardly effected the CAC value of the mixed system, while micelle concentration was highly dependent on 458 concentration. This phenomenon may be explained as the weak binding affinity of 458, which has a flexible conformation without hydrogen bonds at the lower rim since methylation of lower-rim hydroxyls results in loss of hydrogen bonds, leading to a flexible conformation of 458.
3.2.2 Host-regulated morphology. Following the same principle as guest induced amphiphilic calixarene aggregation, SCnAs reduced electrostatic repulsion of surfactants also leads to a larger size aggregation with a smaller curvature. Many examples of arrangement transfer from small micelles to vesicles were reported, with a significant Tyndall effect. For instance, the aggregation of 454 and an asymmetric viologen G35 was studied by DLS, TEM, and SEM.297 The DLS result showed that the average diameter of the aggregates was 362 nm, with a narrow size distribution. TEM and SEM images showed the hollow spherical morphology, indicating convincingly the vesicular structure. Moreover, the thickness of the bilayer membrane obtained was about 7 nm, which was almost equal to the total height of lengths of two G35 and two 454.

Harangozo and coworkers reported a nanoparticle consisting of G42 and SC6A (456).307 Small angle neutron scattering (SANS) and cryo-TEM results indicated that the diameter of the multilayered nanoparticles was around 160 nm. Interestingly, they found that the nanoparticles have a tendency to transform into supramolecular micelles (around 6 nm diameter) in the presence of NaCl (Fig. 7c), which may be due to additional ions interfering the hydrate structure around the hydrophobic chains and the cross-sectional area of this supra-amphiphile.


image file: c9qm00489k-f7.tif
Fig. 7 (a) Schematic illustration of the complex-induced aggregation of BPTA-PBI (G21) by 454 and 455. Reprinted with permission from ref. 298. Copyright 2012 from Royal Society of Chemistry. (b) Schematic representation of the construction of a supramolecular binary vesicle based on the host–guest complexation of 454 with G35. Reprinted with permission from ref. 297. Copyright 2011 from American Chemical Society. (c) Illustration of 454 induced G42 formation of nanoparticles and supramolecular micelles. Reprinted with permission from ref. 307. Copyright 2016 from American Chemical Society.

Besides the size of assemblies, SCnA could also modulate their shape. Guo and coworkers studied the morphology of the SC5A 455 and G21 aggregates.298 The TEM image of free G21 showed some irregular arrangement without a specific topological structure, while nano-rod structures with an average length of 220 nm appeared in the presence of 455. These rods are considered to be composed of bundles of fibers, resulting from the hierarchical assembly of calixarenes (Fig. 7).

3.2.3 Host-enhanced packing compactness. Direct evidence of enhancing the packing compactness is the XRD results of G21. As reported by Guo and coworkers, free G21 shows a π–π stacking distance of 3.54 Å, while the results are 3.42 and 3.39 Å in the presence of 454 and 455, respectively (Fig. 7a).298

However, measuring XRD is not suitable for every assembly. So the García-Río group and the Biczok group took hydrophobicity of assembly as a parameter for compactness comparison. They assumed that a more hydrophobic assembly means more compactness.

Basilio and coworkers measured the hydrophobicity of dodecyltrimethylammonium bromide (G10) assembly by measuring the hydrolysis rate of two kinetic probes.314 Hydrolysis rates at different surfactant concentrations were plotted and fitted, from which the binding constant of the kinetic probe between the micelles and the bulk water (KSm) was obtained. The KSm value of G10 in the absence of 458 is smaller than that in the presence of 458, which means the addition of 458 leads to stronger hydrophobicity of aggregates.

Biczok and coworkers investigated the polarity of interfacial layers by using a fluorescent probe, from whose maximum fluorescence emission wavelength, the local polarity around the probe can be determined.307 The polarity results were in the order 456G42 supramolecular micelle <457G42 supramolecular micelle <G42 micelle, which indicated more compact stacking of micelles.

3.3 Mutual inducement

In addition to the aforementioned two complexation-induced aggregation strategies, mutual inducement involves a larger range of host and guest molecules to fabricate supra-amphiphiles. For example, amphiphilic hosts and amphiphilic guests generate new supra-amphiphiles with different CACs and morphologies.251,304,324 Hydrophilic hosts and hydrophobic drugs form supra-amphiphiles which can be applied in medical diagnosis and treatment.325,326 Hydrophilic hosts and polymers, especially biomacromolecules like protein, DNA, and chitosan, are able to mutually induce aggregation.77,205,227,304,327–330 Supra-amphiphiles consisting of various kinds of host and guest molecules not only enrich the supra-amphiphile concept but also promise potential applications such as drug delivery and gene transfection.

4. Conclusion and outlook

In this review, we systematically summarized the assembling features of calixarene-based amphiphiles and supra-amphiphiles. Hundreds of amphiphilic calixarenes were fabricated by facile covalent modification, including upper-rim hydrophilic amphiphiles, lower-rim hydrophilic amphiphiles and bola-type amphiphiles. Compared with conventional amphiphiles, amphiphilic calixarenes usually show lower CACs and more diverse morphologies. Moreover, amphiphilic calixarenes are able to form uniform assemblies with precise Naggs. The assemblies of amphiphilic calixarenes pack more compactly than those of common surfactants and their assembling kinetics is much slower. The preorganized framework of calixarenes is the most important factor to influence these unique assembly properties. In general, a larger number of repeat units lead to higher assembling tendency when the conformation is fixed, and the cone conformation is more beneficial to aggregation than the alternative conformation.

On the other hand, benefiting from their cavities, aggregation of amphiphilic calixarenes could be induced by various guests. Similarly, hydrophilic calixarenes possess the ability to enhance the assembly of amphiphilic guests. These induced aggregation phenomena are due to additional attractive interactions decreasing the repulsion of head groups of amphiphiles. Construction of such supra-amphiphiles avoids tedious synthesis, and the obtained assemblies also bear the properties of low CAC, regular morphology, and compact packing.

With prosperous development, there are still some promising objectives and challenges for the development of this area. First, the fundamental studies of assembly behaviors, such as the relationship between molecular structures and assembly properties, compactness and kinetics, need to be systematical investigated urgently. Up to now, hundreds of amphiphilic calixarenes as well as their CACs and morphologies have been reported, but there is no appropriate rule to describe how these properties depend on structures, which is extremely important to rational design of amphiphilic calixarenes with superior performance. On the other hand, compactness and kinetics behavior are featured properties of amphiphilic calixarenes, but only demonstrated in limited works. More attention is needed in the future because they are not only the important fundamental topics, but also related to further applications. For example, compact vesicles provide reliable platforms for capsuling cargo and constructing fluorescence materials with high efficiency,46,180 while the kinetics feature is critical for preparation procedures of these materials.

Second, crosslinking represents a convenient avenue to obtain assemblies with better stability. For instance, Shulov and coworkers proposed a new platform for bioimaging by cyanine 3 and cyanine 5 corona crosslinked calixarene micelles.60 The obtained protein-sized nanoparticles present excellent stability in various environments, showing a high fluorescence signal to noise ratio without dye leakage. Crosslinking can also be employed on the basis of supra-amphiphiles. Peng and coworkers constructed a novel supramolecular crosslinked vesicle by post-modification of a dynamic SC4A-(dodecyloxybenzyl)tripropargylammonium vesicle with the “click” reaction.331 The obtained vesicle is stable enough in diverse and complex surroundings and can be disrupted with specific chemical stimuli to realize controlled release. These pioneering works demonstrate the advantages of the crosslinking strategy, which may inspire more fascinating applications in the future.

Third, by combining amphiphilic calixarenes with various kinds of other amphiphiles, such as conventional surfactants, phospholipids or macrocyclic amphiphiles, the obtained co-assemblies exhibit different assembly behaviors. Co-assembled amphiphiles may introduce attractive interactions between hydrophilic head groups of amphiphilic calixarenes, leading to lower CACs and various morphologies.66 Moreover, calixarene conformations may be regulated by co-assembling, resulting in better binding affinity.86 Besides, co-assembly of different amphiphilic macrocycles enables heteromultivalent recognition.179

Last but not least, although the cavities of calixarenes are well utilized in supra-amphiphiles, they have not attracted much attention in calixarene amphiphilic assemblies up to now. Actually, binding and assembling abilities complement each other and influence each other. As we mentioned above, aggregation enhances the binding ability by regulating the calixarene conformation.86 Furthermore, by utilizing the host–guest recognition cavity of calixarenes on the assembly surface, the morphology of the assembly can be controlled by guests, non-covalent modification of specific functional groups can be performed, and multidimensional and hierarchical self-assemblies can be achieved.

In summary, aiming on these objectives and challenges will lead to a deep understanding of the assembling features of amphiphiles and supra-amphiphiles based on calixarenes, and also enrich their construction motifs and strategies, which are essential to develop functional materials based on calixarenes. Moreover, although this review focused on calixarenes, the conclusions are also transferable to other macrocyclic amphiphiles and supra-amphiphiles.

Conflicts of interest

There are no conflicts to declare.

Acknowledgements

This work was supported by the NSFC (51873090 and 21672112), the Fundamental Research Funds for the Central Universities and the Innovation Project of Hebei Province (19241303D), which are gratefully acknowledged.

Notes and references

  1. Y. Chang, Y. Jiao, H. E. Symons, J. F. Xu, C. F. J. Faul and X. Zhang, Chem. Soc. Rev., 2019, 48, 989–1003 RSC.
  2. A. Sorrenti, O. Illa and R. M. Ortuno, Chem. Soc. Rev., 2013, 42, 8200–8219 RSC.
  3. Y.-C. Liu, H.-W. Sun and D.-S. Guo, Curr. Org. Chem., 2018, 22, 2127–2149 CrossRef CAS.
  4. Y. Yao, R.-B. Zhao, Y.-J. Shi, Y. Cai, J. Chen, S.-Y. Sun, W. Zhang and R.-K. Tang, Chem. Commun., 2018, 54, 8068–8071 RSC.
  5. S. Shinkai, S. Mori, H. Koreishi, T. Tsubaki and O. Manabe, J. Am. Chem. Soc., 1986, 108, 2409–2416 CrossRef CAS.
  6. G. Varan, C. Varan, N. Erdogar, A. A. Hincal and E. Bilensoy, Int. J. Pharm., 2017, 531, 457–469 CrossRef CAS PubMed.
  7. J. Gao and D.-S. Guo, Sci. Sin.: Chim., 2019, 49, 811–820 Search PubMed.
  8. H. Zhang, Z. Liu and Y. Zhao, Chem. Soc. Rev., 2018, 47, 5491–5528 RSC.
  9. S.-Y. Sun, M. Geng, L. Huang, Y.-M. Chen, M.-P. Cen, D. Lu, A.-W. Wang, Y. Wang, Y.-J. Shi and Y. Yao, Chem. Commun., 2018, 54, 13006–13009 RSC.
  10. X. Zhang and C. Wang, Chem. Soc. Rev., 2011, 40, 94–101 RSC.
  11. G.-C. Yu, K.-C. Jie and F.-H. Huang, Chem. Rev., 2015, 115, 7240–7303 CrossRef CAS.
  12. D.-Y. Xia, Y. Li, K.-C. Jie, B.-B. Shi and Y. Yao, Org. Lett., 2016, 18, 2910–2913 CrossRef CAS.
  13. C. D. Gutsche, Acc. Chem. Res., 1983, 16, 161–170 CrossRef CAS.
  14. V. Bohmer, Angew. Chem., Int. Ed. Engl., 1995, 34, 713–745 CrossRef.
  15. K. Helttunen and P. Shahgaldian, New J. Chem., 2010, 34, 2704–2714 RSC.
  16. N. Basilio, V. Francisco and L. Garcia-Rio, Int. J. Mol. Sci., 2013, 14, 3140–3157 CrossRef CAS.
  17. R. V. Rodik, A. S. Klymchenko, Y. Mely and V. I. Kalchenko, J. Inclusion Phenom. Macrocyclic Chem., 2014, 80, 189–200 CrossRef CAS.
  18. J. Wang, X. Ding and X. Guo, Adv. Colloid Interface Sci., 2019, 269, 187–202 CrossRef CAS.
  19. S. Kolusheva, O. Molt, M. Herm, T. Schrader and R. Jelinek, J. Am. Chem. Soc., 2005, 127, 10000–10001 CrossRef CAS.
  20. T. Sun, L.-R. Qi, W.-W. Li, Y. Li, X.-M. Shuai, Z.-Q. Cai, H.-P. Chen, X.-G. Qiao and L.-F. Ma, J. Chromatogr. A, 2019, 1601, 310–318 CrossRef CAS PubMed.
  21. V. I. Kalchenko, Theor. Exp. Chem., 2018, 54, 74–84 CrossRef CAS.
  22. A. B. Mirgorodskaya, E. I. Yackevich, Y. R. Kudryashova, R. R. Kashapov, S. E. Solovieva, A. T. Gubaidullin, I. S. Antipin, L. Y. Zakharova and A. I. Konovalov, Colloids Surf., B, 2014, 117, 497–504 CrossRef CAS PubMed.
  23. E. J. Cho, J. K. Kang, W. S. Han and J. H. Jung, Langmuir, 2008, 24, 5229–5232 CrossRef CAS.
  24. J. Luo and Y.-S. Zheng, Prog. Chem., 2018, 30, 601–615 Search PubMed.
  25. Z. Xu, D. Gonzalez-Abradelo, J. Li, C. A. Strassert, B. J. Ravoo and D.-S. Guo, Mater. Chem. Front., 2017, 1, 1847–1852 RSC.
  26. Z. Zheng, W.-C. Geng, Z. Xu and D.-S. Guo, Isr. J. Chem., 2019, 59, 1–16 CrossRef.
  27. W.-C. Geng, Q. Huang, Z. Xu, R. Wang and D.-S. Guo, Theranostics, 2019, 9, 3094–3106 CrossRef CAS.
  28. E. S. Espanol and M. M. Villamil, Biomolecules, 2019, 9 DOI:10.3390/biom9030090.
  29. J. Gao and D.-S. Guo, Sci. Sin.: Chim., 2018, 48, 949–956 Search PubMed.
  30. J. L. J. Blanco, J. M. Benito, C. O. Mellet and J. M. G. Fernandez, J. Drug Delivery Sci. Technol., 2017, 42, 18–37 CrossRef.
  31. S. Karakurt, T. F. Kellici, T. Mavromoustakos, A. G. Tzakos and M. Yilmaz, Curr. Org. Chem., 2016, 20, 1043–1057 CrossRef CAS.
  32. Y. Zhou, H. Li and Y.-W. Yang, Chin. Chem. Lett., 2015, 26, 825–828 CrossRef CAS.
  33. X. Ma and Y. Zhao, Chem. Rev., 2015, 115, 7794–7839 CrossRef CAS.
  34. M. Giuliani, I. Morbioli, F. Sansone and A. Casnati, Chem. Commun., 2015, 51, 14140–14159 RSC.
  35. M.-F. Ma, P.-Y. Xing, S.-Y. Li, X.-X. Chu, B. Wang and A.-Y. Hao, Prog. Chem., 2014, 26, 1317–1328 CAS.
  36. K.-C. Jie, Y.-J. Zhou, Y. Yao and F.-H. Huang, Chem. Soc. Rev., 2015, 44, 3568–3587 RSC.
  37. S. Sayin and M. Yilmaz, Tetrahedron, 2016, 72, 6528–6535 CrossRef CAS.
  38. J. J. Michels, J. Huskens, J. F. J. Engbersen and D. N. Reinhoudt, Langmuir, 2000, 16, 4864–4870 CrossRef CAS.
  39. M. Moradi, L. G. Tulli, J. Nowakowski, M. Baljozovic, T. A. Jung and P. Shahgaldian, Angew. Chem., Int. Ed., 2017, 56, 14395–14399 CrossRef CAS.
  40. Z.-F. Xiao, W.-P. Yang, F.-Y. Yan, L.-B. Ji, W. Li and W. Wang, CrystEngComm, 2019, 21, 439–448 RSC.
  41. K. Suwinska, O. Shkurenko, C. Mbemba, A. Leydier, S. Jebors, A. W. Coleman, R. Matar and P. Falson, New J. Chem., 2008, 32, 1988–1998 RSC.
  42. M. Strobel, K. Kita-Tokarczyk, A. Taubert, C. Vebert, P. A. Heiney, M. Chami and W. Meier, Adv. Funct. Mater., 2006, 16, 252–259 CrossRef CAS.
  43. P. K. Eggers, T. Becker, M. K. Melvin, R. A. Boulos, E. James, N. Morellini, A. R. Harvey, S. A. Dunlop, M. Fitzgerald, K. A. Stubbs and C. L. Raston, RSC Adv., 2012, 2, 6250–6257 RSC.
  44. Q. Zhao, Y. Chen, S. H. Li and Y. Liu, Chem. Commun., 2018, 54, 200–203 RSC.
  45. S. E. Sestito, F. A. Facchini, I. Morbioli, J. M. Billod, S. Martin-Santamaria, A. Casnati, F. Sansone and F. Peri, J. Med. Chem., 2017, 60, 4882–4892 CrossRef CAS.
  46. Z. Xu, S. Peng, Y.-Y. Wang, J.-K. Zhang, A. I. Lazar and D.-S. Guo, Adv. Mater., 2016, 28, 7666–7671 CrossRef CAS.
  47. K. I. Assaf, A. Hennig, S. Peng, D.-S. Guo, D. Gabel and W. M. Nau, Chem. Commun., 2017, 53, 4616–4619 RSC.
  48. V. A. Burilov, G. A. Fatikhova, D. A. Mironova, S. E. Solovieva and I. S. Antipin, Macroheterocycles, 2015, 8, 409–414 CrossRef CAS.
  49. S. Shinkai, T. Arimura, K. Araki and H. Kawabata, J. Chem. Soc., Perkin Trans. 1, 1989, 2039–2045 RSC.
  50. J. Cui, V. D. Uzunova, D.-S. Guo, K. Wang, W. M. Nau and Y. Liu, Eur. J. Org. Chem., 2010, 1704–1710 CrossRef CAS.
  51. X.-P. Ding, D.-B. Tang, T. Li, S.-F. Wang and Y.-Y. Zhou, Spectrochim. Acta, Part A, 2011, 81, 44–47 CrossRef CAS.
  52. N. Basilio, V. Francisco and L. Garcia-Rio, J. Org. Chem., 2012, 77, 10764–10772 CrossRef CAS.
  53. N. Basilio and L. Garcia-Rio, ChemPhysChem, 2012, 13, 2368–2376 CrossRef CAS.
  54. N. Basilio, L. Garcia-Rio and M. Martin-Pastor, Langmuir, 2012, 28, 2404–2414 CrossRef CAS.
  55. X.-Y. Hu, S. Peng, D.-S. Guo, F. Ding and Y. Liu, Supramol. Chem., 2015, 27, 336–345 CrossRef CAS.
  56. Y.-C. Pan, H.-W. Tian, S. Peng, X.-Y. Hu and D.-S. Guo, Chin. Chem. Lett., 2017, 28, 787–792 CrossRef CAS.
  57. S. Fernandez-Abad, M. Pessego, N. Basilio and L. Garcia-Rio, Chem. – Eur. J., 2016, 22, 6466–6470 CrossRef CAS.
  58. Y.-X. Wang, Y.-M. Zhang, Y.-L. Wang and Y. Liu, Chem. Mater., 2015, 27, 2848–2854 CrossRef CAS.
  59. M. Esmaielzade Rostami, B. Gorji and R. Zadmard, Tetrahedron Lett., 2018, 59, 2393–2398 CrossRef CAS.
  60. I. Shulov, R. V. Rodik, Y. Arntz, A. Reisch, V. I. Kalchenko and A. S. Klymchenko, Angew. Chem., Int. Ed., 2016, 55, 15884–15888 CrossRef CAS.
  61. S. Kolusheva, R. Zadmard, T. Schrader and R. Jelinek, J. Am. Chem. Soc., 2006, 128, 13592–13598 CrossRef CAS PubMed.
  62. S. Peng, A. Barba-Bon, Y.-C. Pan, W. M. Nau, D.-S. Guo and A. Hennig, Angew. Chem., Int. Ed., 2017, 56, 1–5 CrossRef.
  63. S. Fujii, S. Yamada, S. Matsumoto, G. Kubo, K. Yoshida, E. Tabata, R. Miyake, Y. Sanada, I. Akiba, T. Okobira, N. Yagi, E. Mylonas, N. Ohta, H. Sekiguchi and K. Sakurai, Sci. Rep., 2017, 7, 44494 CrossRef CAS.
  64. S. Fujii, J. H. Lee, R. Takahashi and K. Sakurai, Langmuir, 2018, 34, 5072–5078 CrossRef CAS.
  65. S. Fujii, R. Takahashi, J. H. Lee and K. Sakurai, Soft Matter, 2018, 14, 875–878 RSC.
  66. J. H. Lee, S. Fujii, R. Takahashi and K. Sakurai, Chem. Commun., 2019, 55, 1303–1305 RSC.
  67. D. Elend, U. Pieles and P. Shahgaldian, Chimia, 2010, 64, 45–48 CrossRef CAS.
  68. N. Moridi, O. Danylyuk, K. Suwinska and P. Shahgaldian, J. Colloid Interface Sci., 2012, 377, 450–455 CrossRef CAS.
  69. L. G. Tulli, N. Moridi, W. Wang, K. Helttunen, M. Neuburger, D. Vaknin, W. Meier and P. Shahgaldian, Chem. Commun., 2014, 50, 3938–3940 RSC.
  70. L. G. Tulli, W. Wang, W. R. Lindemann, I. Kuzmenko, W. Meier, D. Vaknin and P. Shahgaldian, Langmuir, 2015, 31, 2351–2359 CrossRef CAS.
  71. N. O. Mchedlov-Petrossyan, L. N. Vilkova, N. A. Vodolazkaya, A. G. Yakubovskaya, R. V. Rodik, V. I. Boyko and V. I. Kalchenko, Sensors, 2006, 6, 962–977 CrossRef CAS.
  72. R. V. Rodik, A. S. Klymchenko, N. Jain, S. I. Miroshnichenko, L. Richert, V. I. Kalchenko and Y. Mely, Chem. – Eur. J., 2011, 17, 5526–5538 CrossRef CAS.
  73. N. O. McHedlov-Petrossyan, N. A. Vodolazkaya, R. V. Rodik, L. N. Bogdanova, T. A. Cheipesh, O. Y. Soboleva, A. P. Kryshtal, L. V. Kutuzova and V. I. Kalchenko, J. Phys. Chem. C, 2012, 116, 10245–10259 CrossRef CAS.
  74. E. V. Ukhatskaya, S. V. Kurkov, M. A. Hjalmarsdottir, V. A. Karginov, S. E. Matthews, R. V. Rodik, V. I. Kalchenko and T. Loftsson, Int. J. Pharm., 2013, 458, 25–30 CrossRef CAS.
  75. E. V. Ukhatskaya, S. V. Kurkov, R. V. Rodik, V. I. Kalchenko, S. E. Matthews, P. Jansook and T. Loftsson, J. Inclusion Phenom. Macrocyclic Chem., 2013, 79, 473–483 CrossRef.
  76. I. O. Melezhyk, R. V. Rodik, N. V. Iavorska, A. S. Klymchenko, Y. Mely, V. V. Shepelevych, L. M. Skivka and V. I. Kalchenko, Anti-Infect. Agents, 2015, 13, 87–94 CrossRef CAS.
  77. R. V. Rodik, A.-S. Anthony, V. I. Kalchenko, Y. Mély and A. S. Klymchenko, New J. Chem., 2015, 39, 1654–1664 RSC.
  78. C. Weeden, K. J. Hartlieb and L. Y. Lim, J. Pharm. Pharmacol., 2012, 64, 1403–1411 CrossRef CAS.
  79. T. Arimura, H. Kawabata, T. Matsuda, T. Muramatsu, H. Satoh, K. Fujio, O. Manabe and S. Shinkai, J. Org. Chem., 1991, 56, 301–306 CrossRef CAS.
  80. D. Hardy, R. M. Bill, A. Jawhari and A. J. Rothnie, Biochem. Soc. Trans., 2016, 44, 838–844 CrossRef CAS.
  81. T. Sun, L.-R. Qi, W.-W. Li, Y. Li, X.-M. Shuai, Z.-Q. Cai, H.-P. Chen, X.-G. Qiao and L.-F. Ma, J. Chromatogr. A, 2019, 1601, 310–318 CrossRef CAS.
  82. H.-Y. Tian, H.-J. Li, Y.-J. Chen, D. Wang and C.-J. Li, Ind. Eng. Chem. Res., 2002, 41, 4523–4527 CrossRef CAS.
  83. T. Jin, F. Fujii, H. Sakata, M. Tamura and M. Kinjo, Chem. Commun., 2005, 4300–4302 RSC.
  84. N. Basilio, L. Garcia-Rio and M. Martin-Pastor, J. Phys. Chem. B, 2010, 114, 4816–4820 CrossRef CAS.
  85. M.-X. Chen, T. Li, S. Peng and D. Tao, New J. Chem., 2016, 40, 9923–9929 RSC.
  86. H.-W. Tian, Y.-C. Pan and D.-S. Guo, Supramol. Chem., 2017, 30, 562–567 CrossRef.
  87. A. Fraix, D. Afonso, G. M. L. Consoli and S. Sortino, Photochem. Photobiol. Sci., 2019, 18, 2216–2224 RSC.
  88. X.-Y. Hu, Y. Chen and Y. Liu, Chin. Chem. Lett., 2015, 26, 862–866 CrossRef CAS.
  89. Y.-X. Wang, D.-S. Guo, Y.-C. Duan, Y.-J. Wang and Y. Liu, Sci. Rep., 2015, 5, 9019 CrossRef CAS.
  90. S. Song, J.-H. Wang, H.-T. Feng, Z.-H. Zhu and Y.-S. Zheng, RSC Adv., 2014, 4, 24909–24913 RSC.
  91. M. S. Becherer, B. Schade, C. Bottcher and A. Hirsch, Chem. – Eur. J., 2009, 15, 1637–1648 CrossRef CAS.
  92. F. Rodler, B. Schade, C. M. Jager, S. Backes, F. Hampel, C. Bottcher, T. Clark and A. Hirsch, J. Am. Chem. Soc., 2015, 137, 3308–3317 CrossRef CAS.
  93. P. Shahgaldian, M. A. Sclotti and U. Pieles, Langmuir, 2008, 24, 8522–8526 CrossRef CAS PubMed.
  94. L. G. Tulli, W.-J. Wang, V. Rullaud, W. R. Lindemann, I. Kuzmenko, D. Vaknin and P. Shahgaldian, RSC Adv., 2016, 6, 9278–9285 RSC.
  95. J. H. Lee, S. Fujii, R. Takahashi and K. Sakurai, Langmuir, 2018, 34, 12109–12115 CrossRef CAS.
  96. M. Fricke, D. Volkmer, C. E. Krill, M. Kellermann and A. Hirsch, Cryst. Growth Des., 2006, 6, 1120–1123 CrossRef CAS.
  97. M. Kellermann, W. Bauer, A. Hirsch, B. Schade, K. Ludwig and C. Bottcher, Angew. Chem., Int. Ed., 2004, 43, 2959–2962 CrossRef CAS PubMed.
  98. C. Yihwa, M. Kellermann, M. Becherer, A. Hirsch and C. Bohne, Photochem. Photobiol. Sci., 2007, 6, 525–531 RSC.
  99. C. M. Jager, A. Hirsch, B. Schade, C. Bottcher and T. Clark, Chem. – Eur. J., 2009, 15, 8586–8592 CrossRef.
  100. I. Di Bari, A. Fraix, R. Picciotto, A. R. Blanco, S. Petralia, S. Conoci, G. Granata, G. M. L. Consoli and S. Sortino, RSC Adv., 2016, 6, 105573 RSC.
  101. I. Di Bari, R. Picciotto, G. Granata, A. R. Blanco, G. M. Consoli and S. Sortino, Org. Biomol. Chem., 2016, 14, 8047–8052 RSC.
  102. G. Granata, I. Paterniti, C. Geraci, F. Cunsolo, E. Esposito, M. Cordaro, A. R. Blanco, S. Cuzzocrea and G. M. L. Consoli, Mol. Pharmaceutics, 2017, 14, 1610–1622 CrossRef CAS.
  103. I. Di Bari, G. Granata, G. M. L. Consoli and S. Sortino, New J. Chem., 2018, 18096–18101 RSC.
  104. S. Friedman, S. Kolusheva, R. Volinsky, L. Zeiri, T. Schrader and R. Jelinek, Anal. Chem., 2008, 80, 7804–7811 CrossRef CAS.
  105. R. Zadmard and T. Schrader, J. Am. Chem. Soc., 2005, 127, 904–915 CrossRef CAS.
  106. Y.-L. Liu, L. Liu, Y.-L. Wang, Y.-C. Han, D. Wong and Y.-J. Chen, Green Chem., 2008, 10, 635–640 RSC.
  107. Z. Zheng, W.-C. Geng, J. Gao, Y.-J. Mu and D.-S. Guo, Org. Chem. Front., 2018, 5, 2685–2691 RSC.
  108. L. Gallego-Yerga, M. Lomazzi, V. Franceschi, F. Sansone, C. Ortiz Mellet, G. Donofrio, A. Casnati and J. M. Garcia Fernandez, Org. Biomol. Chem., 2015, 13, 1708–1723 RSC.
  109. K.-P. Wang, Y. Chen and Y. Liu, Chem. Commun., 2015, 51, 1647–1649 RSC.
  110. X.-M. Chen, Y. Chen, Q. Yu, B.-H. Gu and Y. Liu, Angew. Chem., Int. Ed., 2018, 57, 12519–12523 CrossRef CAS.
  111. G. Granata, G. M. L. Consoli, R. Lo Nigro, G. Malandrino and C. Geraci, Supramol. Chem., 2016, 28, 377–383 CrossRef CAS.
  112. F. Sansone, M. Dudic, G. Donofrio, C. Rivetti, L. Baldini, A. Casnati, S. Cellai and R. Ungaro, J. Am. Chem. Soc., 2006, 128, 14528–14536 CrossRef CAS.
  113. T. Takeuchi, V. Bagnacani, F. Sansone and S. Matile, ChemBioChem, 2009, 10, 2793–2799 CrossRef CAS.
  114. A. D. Martin, E. Houlihan, N. Morellini, P. K. Eggers, E. James, K. A. Stubbs, A. R. Harvey, M. Fitzgerald, C. L. Raston and S. A. Dunlop, ChemPlusChem, 2012, 77, 308–313 CrossRef CAS.
  115. G. M. L. Consoli, G. Granata, R. Picciotto, A. R. Blanco, C. Geraci, A. Marino and A. Nostro, MedChemComm, 2018, 9, 160–164 RSC.
  116. E. James, P. K. Eggers, A. R. Harvey, S. A. Dunlop, M. Fitzgerald, K. A. Stubbs and C. L. Raston, Org. Biomol. Chem., 2013, 11, 6108–6112 RSC.
  117. V. Rullaud, M. Siragusa, A. Cumbo, D. Gygax and P. Shahgaldian, Chem. Commun., 2012, 48, 12186–12188 RSC.
  118. N. Moridi, C. Wackerlin, V. Rullaud, R. Schelldorfer, T. A. Jung and P. Shahgaldian, Chem. Commun., 2013, 49, 367–369 RSC.
  119. V. Rullaud, N. Moridi and P. Shahgaldian, Langmuir, 2014, 30, 8675–8679 CrossRef CAS.
  120. A. Galukhin, A. Erokhin, I. Imatdinov and Y. Osin, RSC Adv., 2015, 5, 33351–33355 RSC.
  121. W.-C. Geng, Y.-C. Liu, Y.-Y. Wang, Z. Xu, Z. Zheng, C.-B. Yang and D.-S. Guo, Chem. Commun., 2016, 53, 392–395 RSC.
  122. S. Fujii, Y. Sanada, T. Nishimura, I. Akiba, K. Sakurai, N. Yagi and E. Mylonas, Langmuir, 2012, 28, 3092–3101 CrossRef CAS.
  123. S. Sakamoto, S. Fujii, K. Yoshida and K. Sakurai, Langmuir, 2016, 32, 12434–12441 CrossRef CAS.
  124. M. Araki, S. Fujii, J. H. Lee, R. Takahashi and K. Sakurai, Soft Matter, 2019, 3515–3519 RSC.
  125. E. Mylonas, N. Yagi, S. Fujii, K. Ikesue, T. Ueda, H. Moriyama, Y. Sanada, K. Uezu, K. Sakurai and T. Okobira, Sci. Rep., 2019, 9, 1982 CrossRef.
  126. E. Houel, A. Lazar, E. Da Silva, A. W. Coleman, A. Solovyov, S. Cherenok and V. I. Kalchenko, Langmuir, 2002, 18, 1374–1379 CrossRef CAS.
  127. M. Rehm, M. Frank and J. Schatz, Tetrahedron Lett., 2009, 50, 93–96 CrossRef CAS.
  128. J. Gasparello, A. Manicardi, A. Casnati, R. Corradini, R. Gambari, A. Finotti and F. Sansone, Sci. Rep., 2019, 9, 3036 CrossRef.
  129. A. D. Martin, R. A. Boulos, K. A. Stubbs and C. L. Raston, Chem. Commun., 2011, 47, 7329–7331 RSC.
  130. J. Mo, L. Wang, X. Huang, B. Lu, C. Zou, L. Wei, J. Chu, P. K. Eggers, S. Chen, C. L. Raston, J. Wu, L. Y. Lim and W. Zhao, Nanoscale, 2017, 9, 13142–13152 RSC.
  131. K. Samanta, D. S. Ranade, A. Upadhyay, P. P. Kulkarni and C. P. Rao, ACS Appl. Mater. Interfaces, 2017, 9, 5109–5117 CrossRef CAS.
  132. S. Arimori, T. Nagasaki and S. Shinkai, J. Chem. Soc., Perkin Trans. 1, 1993, 887–889 RSC.
  133. R. Takahashi, S. Matsumoto, S. Fujii, T. Narayanan and K. Sakurai, Angew. Chem., Int. Ed., 2017, 56, 6734–6738 CrossRef CAS.
  134. E. V. Ukhatskaya, S. V. Kurkov, S. E. Matthews, A. El Fagui, C. Amiel, F. Dalmas and T. Loftsson, Int. J. Pharm., 2010, 402, 10–19 CrossRef CAS.
  135. E. V. Ukhatskaya, S. V. Kurkov, S. E. Matthews and T. Loftsson, J. Inclusion Phenom. Macrocyclic Chem., 2013, 79, 47–55 CrossRef.
  136. V. A. Burilov, G. A. Fatikhova, M. N. Dokuchaeva, R. I. Nugmanov, D. A. Mironova, P. V. Dorovatovskii, V. N. Khrustalev, S. E. Solovieva and I. S. Antipin, Beilstein J. Org. Chem., 2018, 14, 1980–1993 CrossRef CAS.
  137. R. Zadmard, M. Arendt and T. Schrader, J. Am. Chem. Soc., 2004, 126, 7752–7753 CrossRef CAS.
  138. Y.-X. Wang, D.-S. Guo, Y. Cao and Y. Liu, RSC Adv., 2013, 3, 8058–8063 RSC.
  139. S. Fujii, K. Sakurai, T. Okobira, N. Ohta and A. Takahara, Langmuir, 2013, 29, 13666–13675 CrossRef CAS.
  140. S. Fujii, R. Takahashi and K. Sakurai, Langmuir, 2017, 33, 4019–4027 CrossRef CAS.
  141. E.-H. Ryu, J. Yan, Z. Zhong and Y. Zhao, J. Org. Chem., 2006, 71, 7205–7213 CrossRef CAS.
  142. K. Khan, H. Huang and Y.-S. Zheng, Curr. Org. Chem., 2012, 16, 2745–2751 CrossRef CAS.
  143. K. Khan, S. L. Badshah, N. Ahmad, H. U. Rashid and Y. Mabkhot, Molecules, 2017, 22, 783 CrossRef.
  144. T. Mecca, G. M. Messina, G. Marletta and F. Cunsolo, Chem. Commun., 2013, 49, 2530–2532 RSC.
  145. E.-H. Ryu and Y. Zhao, Org. Lett., 2004, 6, 3187–3189 CrossRef CAS.
  146. H. Huang, D.-M. Li, W. Wang, Y.-C. Chen, K. Khan, S. Song and Y.-S. Zheng, Org. Biomol. Chem., 2012, 10, 729–735 RSC.
  147. H. Matsuoka, M. Tsurumi and N. Ise, Phys. Rev. B: Condens. Matter Mater. Phys., 1988, 38, 6279–6286 CrossRef CAS.
  148. H.-Y. Tian, Y.-J. Chen, D. Wang, C. C. Zeng and C. J. Li, Tetrahedron Lett., 2000, 41, 2529–2532 CrossRef CAS.
  149. S. Avvakumova, P. Fezzardi, L. Pandolfi, M. Colombo, F. Sansone, A. Casnati and D. Prosperi, Chem. Commun., 2014, 50, 11029–11032 RSC.
  150. K. Yoshida, S. Fujii, R. Takahashi, S. Matsumoto and K. Sakurai, Langmuir, 2017, 33, 9122–9128 CrossRef CAS.
  151. S. Shinkai, H. Koreishi, H. Mori, T. Sone and O. Manabe, Chem. Lett., 1985, 1033–1036 CrossRef CAS.
  152. L.-T. Zhang, L. A. Godinez, T.-B. Lu, G. W. Gokel and A. E. Kaifer, Angew. Chem., Int. Ed. Engl., 1995, 34, 235–237 CrossRef CAS.
  153. Y.-J. Zhang and W.-X. Cao, New J. Chem., 2001, 25, 483–486 RSC.
  154. I. S. Ryzhkina, Y. V. Kiseleva, L. I. Murtazina, S. E. Solovieva, N. G. Manin and A. I. Konovalov, Macroheterocycles, 2017, 10, 190–195 CrossRef CAS.
  155. S. Houmadi, D. Coquiere, L. Legrand, M. C. Faure, M. Goldmann, O. Reinaud and S. Remita, Langmuir, 2007, 23, 4849–4855 CrossRef CAS.
  156. N. Micali, V. Villari, G. M. Consoli, F. Cunsolo and C. Geraci, Phys. Rev. E: Stat., Nonlinear, Soft Matter Phys., 2006, 73, 051904 CrossRef PubMed.
  157. R. Miyake, S. Fujii, J. H. Lee, R. Takahashi and K. Sakurai, J. Colloid Interface Sci., 2019, 535, 8–15 CrossRef CAS.
  158. Y. Tokunaga, H. Sakon, H. Kanefusa, Y. Shimomura and K. Suzuki, ARKIVOC, 2003, 135–143 Search PubMed.
  159. J. Dauvergne, E. M. Desuzinges, C. Faugier, S. Igonet, M. Soulié, E. Grousson, D. Cornut, F. Bonneté, G. Durand, E. Dejean and A. Jawhari, ChemistrySelect, 2019, 4, 5535–5539 Search PubMed.
  160. S. Shinkai, Y. Shirahama, T. Tsubaki and O. Manabe, J. Chem. Soc., Perkin Trans. 1, 1989, 1859–1860 RSC.
  161. J. Zhang, D.-S. Guo, L.-H. Wang, Z. Wang and Y. Liu, Soft Matter, 2011, 7, 1756–1762 RSC.
  162. Z. Wang, D.-S. Guo, J. Zhang and Y. Liu, Acta Chim. Sin., 2012, 70, 1709 CrossRef CAS.
  163. L. Gallego-Yerga, M. Lomazzi, F. Sansone, C. Ortiz Mellet, A. Casnati and J. M. Garcia Fernandez, Chem. Commun., 2014, 50, 7440–7443 RSC.
  164. L. Gallego-Yerga, I. Posadas, C. de la Torre, J. Ruiz-Almansa, F. Sansone, C. Ortiz Mellet, A. Casnati, J. M. Garcia Fernandez and V. Cena, Front. Pharmacol., 2017, 8, 249 CrossRef.
  165. X. Yan, V. Janout, J. T. Hsu and S. L. Regen, J. Am. Chem. Soc., 2003, 125, 8094–8095 CrossRef CAS.
  166. D. H. McCullough, V. Janout, J. W. Li, J. T. Hsu, Q. Truong, E. Wilusz and S. L. Regen, J. Am. Chem. Soc., 2004, 126, 9916–9917 CrossRef CAS.
  167. S. Fujii, K. Nishina, S. Yamada, S. Mochizuki, N. Ohta, A. Takahara and K. Sakurai, Soft Matter, 2014, 10, 8216–8223 RSC.
  168. P. Shahgaldian, A. W. Coleman, S. S. Kuduva and M. J. Zaworotko, Chem. Commun., 2005, 1968–1970 RSC.
  169. J. Bugler, N. A. J. M. Sommerdijk, A. J. W. G. Visser, A. van Hoek, R. J. M. Nolte, J. F. J. Engbersen and D. N. Reinhoudt, J. Am. Chem. Soc., 1999, 121, 28–33 CrossRef.
  170. N. Bono, C. Pennetta, A. Sganappa, E. Giupponi, F. Sansone, A. Volonterio and G. Candiani, Int. J. Pharm., 2018, 549, 436–445 CrossRef CAS.
  171. D. Coquiere, J. Marrot and O. Reinaud, Org. Lett., 2007, 9, 3271–3274 CrossRef CAS.
  172. A. V. Solovyov, S. O. Cherenok, O. I. Kalchenko, L. I. Atamas, Z. I. Kazantseva, I. A. Koshets, I. F. Tsymbal and V. I. Kalchenko, J. Mol. Liq., 2011, 159, 117–123 CrossRef CAS.
  173. R. Bussolati, P. Carrieri, A. Secchi, A. Arduini, A. Credi, M. Semeraro, M. Venturi, S. Silvi, D. Velluto, R. Zappacosta and A. Fontana, Org. Biomol. Chem., 2013, 11, 5944–5953 RSC.
  174. D. Vollhardt, J. Gloede, G. Weidemann and R. Rudert, Langmuir, 2003, 19, 4228–4234 CrossRef CAS.
  175. F. Mayer, S. Tiruvadi Krishnan, D. T. Schuhle, S. V. Eliseeva, S. Petoud, E. Toth and K. Djanashvili, Front. Chem., 2018, 6, 1 CrossRef.
  176. Y. Cakmak, T. Nalbantoglu, T. Durgut and E. U. Akkaya, Tetrahedron Lett., 2014, 55, 538–540 CrossRef CAS.
  177. O. Kasyan, E. R. Healey, A. Drapailo, M. Zaworotko, S. Cecillon, A. W. Coleman and V. Kalchenko, J. Inclusion Phenom. Macrocyclic Chem., 2006, 58, 127–132 CrossRef.
  178. N. Moridi, D. Elend, O. Danylyuk, K. Suwinska and P. Shahgaldian, Langmuir, 2011, 27, 9116–9121 CrossRef CAS.
  179. Z. Xu, S. Jia, W. Wang, Z. Yuan, B. Jan Ravoo and D.-S. Guo, Nat. Chem., 2019, 11, 86–93 CrossRef CAS.
  180. J. Gao, J. Li, W.-C. Geng, F.-Y. Chen, X.-C. Duan, Z. Zheng, D. Ding and D.-S. Guo, J. Am. Chem. Soc., 2018, 140, 4945–4953 CrossRef CAS.
  181. J. Gao, Z. Zheng, L. Shi, S.-Q. Wu, H. Sun and D.-S. Guo, Beilstein J. Org. Chem., 2018, 14, 1840–1845 CrossRef CAS PubMed.
  182. Y. Zhao and E.-H. Ryu, J. Org. Chem., 2005, 70, 7585–7591 CrossRef CAS.
  183. E.-H. Ryu and Y. Zhao, J. Org. Chem., 2006, 71, 9491–9494 CrossRef CAS.
  184. E.-H. Ryu, H. Cho and Y. Zhao, Org. Lett., 2007, 9, 5147–5150 CrossRef CAS.
  185. M. Lee, S.-J. Lee and L.-H. Jiang, J. Am. Chem. Soc., 2004, 126, 12724–12725 CrossRef CAS PubMed.
  186. Y.-Y. Xie, L.-F. Mao and L.-H. Li, J. Chem. Res., 2013, 476–479 CrossRef CAS.
  187. M. Mori, A. Hirayama, H. Tsue and S. Tanaka, Acta Chromatogr., 2007, 19, 73–80 CAS.
  188. L. S. Yakimova, L. H. Gilmanova, V. G. Evtugyn, Y. N. Osin and I. I. Stoikov, J. Nanopart. Res., 2017, 19, 173 CrossRef.
  189. F. Liu, G.-Y. Lu, W.-J. He, M.-H. Liu and L.-G. Zhu, Thin Solid Films, 2004, 468, 244–249 CrossRef CAS.
  190. P. Shahgaldian, E. Da Silva and A. W. Coleman, J. Inclusion Phenom. Macrocyclic Chem., 2003, 46, 175–177 CrossRef CAS.
  191. D. Momekova, D. Budurova, E. Drakalska, S. Shenkov, G. Momekov, B. Trzebicka, N. Lambov, E. Tashev and S. Rangelov, Int. J. Pharm., 2012, 436, 410–417 CrossRef CAS.
  192. G. Sautrey, I. Clarot, E. Rogalska and J.-B. Regnouf-de-Vains, New J. Chem., 2012, 36, 2060 RSC.
  193. J. Gualbert, P. Shahgaldian and A. W. Coleman, Int. J. Pharm., 2003, 257, 69–73 CrossRef CAS.
  194. G. M. L. Consoli, G. Granata, E. Galante, I. Di Silvestro, L. Salafia and C. Geraci, Tetrahedron, 2007, 63, 10758–10763 CrossRef CAS.
  195. J.-H. Yim, J. Kim, D. W. Gidley, R. S. Vallery, H.-G. Peng, D. K. An, B.-K. Choi, Y.-K. Park and J.-K. Jeon, Macromol. Mater. Eng., 2006, 291, 369–376 CrossRef CAS.
  196. G. Sautrey, I. Clarot, A. B. Salem, E. Rogalska and J.-B. Regnouf de Vains, New J. Chem., 2012, 36, 78–85 RSC.
  197. P. Shahgaldian, A. W. Coleman and V. I. Kalchenko, Tetrahedron Lett., 2001, 42, 577–579 CrossRef CAS.
  198. V. Bagnacani, V. Franceschi, L. Fantuzzi, A. Casnati, G. Donofrio, F. Sansone and R. Ungaro, Bioconjugate Chem., 2012, 23, 993–1002 CrossRef CAS.
  199. D. Volkmer, M. Fricke, M. Gleiche and L.-F. Chi, Mater. Sci. Eng., C, 2005, 25, 161–167 CrossRef.
  200. L. Y. Zakharova, Y. R. Kudryashova, N. M. Selivanova, M. A. Voronin, A. R. Ibragimova, S. E. Solovieva, A. T. Gubaidullin, A. I. Litvinov, I. R. Nizameev, M. K. Kadirov, Y. G. Galyametdinov, I. S. Antipin and A. I. Konovalov, J. Membr. Sci., 2010, 364, 90–101 CrossRef CAS.
  201. P. Shahgaldian and A. W. Coleman, Langmuir, 2003, 19, 5261–5265 CrossRef CAS.
  202. O. M. Martin and S. Mecozzi, Supramol. Chem., 2005, 17, 9–15 CrossRef CAS.
  203. O. M. Martin and S. Mecozzi, Tetrahedron, 2007, 63, 5539–5547 CrossRef CAS.
  204. A. B. Mirgorodskaya, E. I. Yatskevich, Y. R. Kudryashova, S. E. Solov’eva, I. S. Antipin, L. Y. Zakharova and A. I. Konovalov, Kinet. Catal., 2011, 52, 529–535 CrossRef CAS.
  205. Y. R. Kudryashova, F. G. Valeeva, L. Y. Zakharova, S. E. Solovieva, I. S. Antipin, A. T. Gubaidullin and A. I. Konovalov, Colloid J., 2012, 74, 67–77 CrossRef CAS.
  206. B. Korchowiec, A. Ben Salem, Y. Corvis, J. B. R. de Vains, J. Korchowiec and E. Rogalska, J. Phys. Chem. B, 2007, 111, 13231–13242 CrossRef CAS.
  207. M. Pojarova, G. S. Ananchenko, K. A. Udachin, F. Perret, A. W. Coleman and J. A. Ripmeester, New J. Chem., 2007, 31, 871–878 RSC.
  208. A. Mustafina, L. Zakharova, J. Elistratova, J. Kudryashova, S. Soloveva, A. Garusov, I. Antipin and A. Konovalov, J. Colloid Interface Sci., 2010, 346, 405–413 CrossRef CAS PubMed.
  209. A. V. Ten’kovstev, A. B. Razina and M. M. Dudkina, Polym. Sci., Ser. B, 2014, 56, 274–281 CrossRef.
  210. D. Volkmer and M. Fricke, Z. Anorg. Allg. Chem., 2003, 629, 2381–2390 CrossRef CAS.
  211. X. Yu, C.-L. Tu, L. He, R.-B. Wang, G.-M. Sun, D.-Y. Yan and X.-Y. Zhu, J. Macromol. Sci., Part A: Pure Appl. Chem., 2009, 46, 360–367 CrossRef CAS.
  212. D. Volkmer, M. Fricke, D. Vollhardt and S. Siegel, J. Chem. Soc., Dalton Trans., 2002, 4547 RSC.
  213. P.-F. Gou, W.-P. Zhu and Z.-Q. Shen, J. Polym. Sci., Part A: Polym. Chem., 2010, 48, 5643–5651 CrossRef CAS.
  214. R. Roy and J. M. Kim, Angew. Chem., Int. Ed., 1999, 38, 369–372 CrossRef CAS.
  215. P. Shahgaldian, M. Cesario, P. Goreloff and A. W. Coleman, Chem. Commun., 2002, 326–327 RSC.
  216. A. Dubes, I. L. Moudrakovski, P. Shahgaldian, A. W. Coleman, C. I. Ratcliffe and J. A. Ripmeester, J. Am. Chem. Soc., 2004, 126, 6236–6237 CrossRef CAS.
  217. A. Dubes, K. A. Udachin, P. Shahgaldian, A. N. Lazar, A. W. Coleman and J. A. Ripmeester, New J. Chem., 2005, 29, 1141 RSC.
  218. G. S. Ananchenko, M. Pojarova, K. A. Udachin, D. M. Leek, A. W. Coleman and J. A. Ripmeester, Chem. Commun., 2006, 386–388 RSC.
  219. G. S. Ananchenko, K. A. Udachin, M. Pojarova, A. Dubes, J. A. Ripmeester, S. Jebors and A. W. Coleman, Cryst. Growth Des., 2006, 6, 2141–2148 CrossRef CAS.
  220. D. N. Polovyanenko, E. G. Bagryanskaya, A. Schnegg, K. Mobius, A. W. Coleman, G. S. Ananchenko, K. A. Udachin and J. A. Ripmeester, Phys. Chem. Chem. Phys., 2008, 10, 5299–5307 RSC.
  221. P. Shahgaldian, A. W. Coleman, B. Rather and M. J. Zaworotko, J. Inclusion Phenom. Macrocyclic Chem., 2005, 52, 241–245 CrossRef CAS.
  222. X.-L. Lou, F. Cheng, P.-F. Cao, Q. Tang, H.-J. Liu and Y. Chen, Chem. – Eur. J., 2009, 15, 11566–11572 CrossRef CAS.
  223. A. I. Litvinov, F. G. Valeeva, L. Y. Zakharova, S. E. Solovieva, I. S. Antipin and M. K. Kadirov, Russ. Chem. Bull., 2013, 62, 1350–1353 CrossRef CAS.
  224. L. Li, H.-Y. Zhang and Y. Liu, Sci. China: Chem., 2012, 55, 1092–1096 CrossRef CAS.
  225. P. Shahgaldian, Eur. J. Pharm. Biopharm., 2003, 55, 107–113 CrossRef CAS.
  226. P. Shahgaldian, E. Da Silva, A. W. Coleman, B. Rather and M. J. Zaworotko, Int. J. Pharm., 2003, 253, 23–38 CrossRef CAS.
  227. L. Zakharova, Y. Kudryashova, A. Ibragimova, E. Vasilieva, F. Valeeva, E. Popova, S. Solovieva, I. Antipin, Y. Ganeeva, T. Yusupova and A. Konovalov, Chem. Eng. J., 2012, 185–186, 285–293 CrossRef CAS.
  228. N. Maulucci, F. De Riccardis, C. B. Botta, A. Casapullo, E. Cressina, M. Fregonese, P. Tecilla and I. Izzo, Chem. Commun., 2005, 1354–1356 RSC.
  229. G. M. L. Consoli, G. Granata, R. Lo Nigro, G. Malandrino and C. Geraci, Langmuir, 2008, 24, 6194–6200 CrossRef CAS.
  230. M. Mourer, R. E. Duval, P. Constant, M. Daffe and J.-B. Regnouf-de-Vains, ChemBioChem, 2019, 20, 911–921 CrossRef CAS PubMed.
  231. X. Guo, L. Zhang, G.-Y. Lu, M.-F. Yin, F. Liu and M.-H. Liu, Chin. Chem. Lett., 2005, 16, 1543–1546 CAS.
  232. L. Yakimova, P. Padnya, D. Tereshina, A. Kunafina, A. Nugmanova, Y. Osin, V. Evtugyn and I. Stoikov, J. Mol. Liq., 2019, 279, 9–17 CrossRef CAS.
  233. O. M. Martin, L. Yu and S. Mecozzi, Chem. Commun., 2005, 4964–4966 RSC.
  234. Z.-S. Wang, G.-Y. Lu, X. Guo and H.-M. Wu, Supramol. Chem., 2003, 15, 327–334 CrossRef CAS.
  235. E. A. Andreyko, P. L. Padnya and I. I. Stoikov, Colloids Surf., A, 2014, 454, 74–83 CrossRef CAS.
  236. E. A. Andreyko, P. L. Padnya and I. I. Stoikov, J. Phys. Org. Chem., 2015, 28, 527–535 CrossRef CAS.
  237. E. A. Andreyko, P. L. Padnya, R. R. Daminova and I. I. Stoikov, RSC Adv., 2014, 4, 3556–3565 RSC.
  238. F. Liu, Y.-H. Wang and G.-Y. Lu, Chem. Lett., 2005, 34, 1450–1451 CrossRef CAS.
  239. A. R. Esker, L.-H. Zhang, C. E. Olsen, K. No and H. Yu, Langmuir, 1999, 15, 1716–1724 CrossRef CAS.
  240. L. H. Zhang, A. R. Esker, K. No and H. Yu, Langmuir, 1999, 15, 1725–1730 CrossRef CAS.
  241. X. Guo, G.-Y. Lu and Y. Li, Thin Solid Films, 2004, 460, 264–268 CrossRef CAS.
  242. B. Guan, M. Jiang, X.-G. Yang, Q. Liang and Y.-Y. Chen, Soft Matter, 2008, 4, 1393 RSC.
  243. S. Jebors, G. S. Ananchenko, A. W. Coleman and J. A. Ripmeester, Tetrahedron Lett., 2007, 48, 5503–5506 CrossRef CAS.
  244. S. Jebors, F. Fache, S. Balme, F. Devoge, M. Monachino, S. Cecillon and A. W. Coleman, Org. Biomol. Chem., 2008, 6, 319–329 RSC.
  245. F. A. Loiseau, A. M. Hill and K. K. Hii, Tetrahedron, 2007, 63, 9947–9959 CrossRef CAS.
  246. S. Jebors, B. Lesniewska, O. Shkurenko, K. Suwinska and A. W. Coleman, J. Inclusion Phenom. Macrocyclic Chem., 2010, 68, 207–217 CrossRef CAS.
  247. P. L. Padnya, E. A. Andreyko, O. A. Mostovaya, I. K. Rizvanov and I. I. Stoikov, Org. Biomol. Chem., 2015, 13, 5894–5904 RSC.
  248. D. Volkmer, M. Fricke, C. Agena and J. Mattay, J. Mater. Chem., 2004, 14, 2249 RSC.
  249. C. Tu, G. Li, Y. Shi, X. Yu, Y. Jiang, Q. Zhu, J. Liang, Y. Gao, D. Yan, J. Sun and X. Zhu, Chem. Commun., 2009, 3211–3213 RSC.
  250. L. S. Yakimova, P. L. Padnya, A. F. Kunafina, A. R. Nugmanova and I. I. Stoikov, Mendeleev Commun., 2019, 29, 86–88 CrossRef CAS.
  251. G. Gattuso, A. Notti, A. Pappalardo, S. Pappalardo, M. F. Parisi and F. Puntoriero, Tetrahedron Lett., 2013, 54, 188–191 CrossRef CAS.
  252. G. Gattuso, A. Notti, S. Pappalardo, M. F. Parisi, I. Pisagatti and S. Patanè, New J. Chem., 2014, 38, 5983–5990 RSC.
  253. G. Arena, A. Pappalardo, S. Pappalardo, G. Gattuso, A. Notti, M. F. Parisi, I. Pisagatti and C. Sgarlata, J. Therm. Anal. Calorim., 2015, 121, 1073–1079 CrossRef CAS.
  254. L. Barbera, G. Gattuso, F. H. Kohnke, A. Notti, S. Pappalardo, M. F. Parisi, I. Pisagatti, S. Patane, N. Micali and V. Villari, Org. Biomol. Chem., 2015, 13, 6468–6473 RSC.
  255. W.-P. Zhu, J. Ling and Z.-Q. Shen, Macromol. Chem. Phys., 2006, 207, 844–849 CrossRef CAS.
  256. A. V. Ten'kovtsev and A. B. Razina, Russ. J. Appl. Chem., 2009, 82, 1615–1619 CrossRef.
  257. I. Pisagatti, L. Barbera, G. Gattuso, S. Patanè, M. F. Parisi and A. Notti, Supramol. Chem., 2018, 30, 658–663 CrossRef CAS.
  258. A. V. Tenkovtsev, M. M. Dudkina, L. I. Scherbinskaya, V. Aseyev and H. Tenhu, Polymer, 2010, 51, 3108–3115 CrossRef CAS.
  259. Z.-M. Zhao, Y. Wang, J. Han, H.-D. Zhu and L. An, Chem. Pharm. Bull., 2015, 63, 180–186 CrossRef CAS PubMed.
  260. G. de Miguel, M. T. Martin-Romero, J. M. Pedrosa, E. Munoz, M. Perez-Morales, T. H. Richardson and L. Camacho, Phys. Chem. Chem. Phys., 2008, 10, 1569–1576 RSC.
  261. G. de Miguel, M. T. Martin-Romero, M. Perez-Morales, E. Munoz and L. Camacho, J. Porphyrins Phthalocyanines, 2009, 13, 597–605 CrossRef CAS.
  262. S. Jebors, A. Leydier, Q. Wu, B. Bertino Ghera, M. Malbouyre and A. W. Coleman, J. Microencapsulation, 2010, 27, 561–571 CrossRef CAS PubMed.
  263. A. M. Gonzalez-Delgado, J. J. Giner-Casares, G. Brezesinski, J. B. Regnouf-de-Vains and L. Camacho, Langmuir, 2012, 28, 12114–12121 CrossRef CAS PubMed.
  264. U. Darbost, M. Giorgi, N. Hucher, I. Jabin and O. Reinaud, Supramol. Chem., 2005, 17, 243–250 CrossRef CAS.
  265. Z. Rafiee, A. Kakanejadifard, R. Hosseinzadeh, M. Nemati and M. Adeli, RSC Adv., 2016, 6, 17470–17473 RSC.
  266. V. A. Burilov, D. A. Mironova, R. R. Ibragimova, R. I. Nugmanov, S. E. Solovieva and I. S. Antipin, Colloids Surf., A, 2017, 515, 41–49 CrossRef CAS.
  267. R. R. Ibragimova, V. A. Burilov, A. R. Aimetdinov, D. A. Mironova, V. G. Evtugyn, Y. N. Osin, S. E. Solovieva and I. S. Antipin, Macroheterocycles, 2016, 9, 433–441 CrossRef CAS.
  268. V. Burilov, A. Valiyakhmetova, D. Mironova, E. Sultanova, V. Evtugyn, Y. Osin, S. Katsyuba, T. Burganov, S. Solovieva and I. Antipin, New J. Chem., 2018, 42, 2942–2951 RSC.
  269. V. A. Burilov, R. I. Nugmanov, R. R. Ibragimova, S. E. Solovieva and I. S. Antipin, Mendeleev Commun., 2015, 25, 177–179 CrossRef CAS.
  270. A. A. Vavilova, V. V. Gorbachuk, D. N. Shurpik, A. V. Gerasimov, L. S. Yakimova, P. L. Padnya and I. I. Stoikov, J. Mol. Liq., 2019, 281, 243–251 CrossRef CAS.
  271. V. A. Burilov, R. R. Ibragimova, B. H. Gafiatullin, R. I. Nugmanov, S. E. Solovieva and I. S. Antipin, Macroheterocycles, 2017, 10, 215–220 CrossRef CAS.
  272. V. A. Burilov, D. A. Mironova, R. R. Ibragimova, S. E. Solovieva, B. König and I. S. Antipin, RSC Adv., 2015, 5, 101177 RSC.
  273. Q. Liang, G.-S. Chen, B. Guan and M. Jiang, J. Mater. Chem., 2011, 21, 13262 RSC.
  274. S. Aleandri, A. Casnati, L. Fantuzzi, G. Mancini, G. Rispoli and F. Sansone, Org. Biomol. Chem., 2013, 11, 4811–4817 RSC.
  275. B. Guan, Q. Liang, Y. Zhu, M.-H. Qiao, J. Zou and M. Jiang, J. Mater. Chem., 2009, 19, 7610–7613 RSC.
  276. Q. Liang, B. Guan and M. Jiang, J. Mater. Chem., 2010, 20, 8236 RSC.
  277. Q. Liang, C. Li, G. Chen and M. Jiang, J. Colloid Interface Sci., 2012, 383, 82–88 CrossRef CAS PubMed.
  278. D. T. Schuhle, J. Schatz, S. Laurent, L. Vander Elst, R. N. Muller, M. C. Stuart and J. A. Peters, Chem. – Eur. J., 2009, 15, 3290–3296 CrossRef PubMed.
  279. J. W. Steed, D. R. Turner and K. J. Wallace, Core concepts in supramolecular chemistry and nanochemistry, Wiley, Chichester, West Succex, England, 2007 Search PubMed.
  280. C. Lau, R. Bitton, H. Bianco-Peled, D. G. Schultz, D. J. Cookson, S. T. Grosser and J. W. Schneider, J. Phys. Chem. B, 2006, 110, 9027–9033 CrossRef CAS PubMed.
  281. M. Miyake, K. Yamada and N. Oyama, Langmuir, 2008, 24, 8527 CrossRef CAS PubMed.
  282. J. N. Israelachvli, D. J. Mitchell and B. W. Ninham, J. Chem. Soc., Faraday Trans. 2, 1976, 72, 1525–1568 RSC.
  283. Q. Liang, B. Guan and M. Jiang, Prog. Chem., 2010, 22, 388–399 CAS.
  284. H.-T. Cui, Y.-M. Feng, W.-Z. Ren, T. Zeng, H.-Y. Lv and Y.-F. Pan, Recent Pat. Nanotechnol., 2009, 3, 32–41 CrossRef CAS PubMed.
  285. N.-M. Hwang, J.-S. Jung and D.-K. Lee, Thermodynamics – Fundamentals and its application in science, InTech, Rijeka, Croatia, 2012 Search PubMed.
  286. E. Mattia and S. Otto, Nat. Nanotechnol., 2015, 10, 111–119 CrossRef CAS PubMed.
  287. C. Wang, Z.-Q. Wang and X. Zhang, Acc. Chem. Res., 2012, 45, 608–618 CrossRef CAS PubMed.
  288. Y. Kang, K. Liu and X. Zhang, Langmuir, 2014, 30, 5989–6001 CrossRef CAS PubMed.
  289. P. Xing, T. Sun and A. Hao, RSC Adv., 2013, 3, 24776–24793 RSC.
  290. C. Wang, Z. Wang and X. Zhang, Small, 2011, 7, 1379–1383 CrossRef CAS PubMed.
  291. Y. Kang, X. Tang, Z. Cai and X. Zhang, Adv. Funct. Mater., 2016, 26, 8920–8931 CrossRef CAS.
  292. X. Zhang, Supramolecular amphiphiles, The Royal Society of Chemistry, London, UK, 2017 Search PubMed.
  293. O. Varga, M. Kubinyi, T. Vidóczy, P. Baranyai, I. Bitter and M. Kállay, J. Photochem. Photobiol., A, 2009, 207, 167–172 CrossRef CAS.
  294. V. Francisco, N. Basilio, L. Garcia-Rio, J. R. Leis, E. F. Maques and C. Vazquez-Vazquez, Chem. Commun., 2010, 46, 6551–6553 RSC.
  295. V. Lau and B. Heyne, Chem. Commun., 2010, 46, 3595–3597 RSC.
  296. M. Megyesi and L. Biczok, J. Phys. Chem. B, 2010, 114, 2814–2819 CrossRef CAS PubMed.
  297. K. Wang, D.-S. Guo, X. Wang and Y. Liu, ACS Nano, 2011, 5, 2880–2894 CrossRef CAS PubMed.
  298. D.-S. Guo, B.-P. Jiang, X. Wang and Y. Liu, Org. Biomol. Chem., 2012, 10, 720–723 RSC.
  299. D.-S. Guo, K. Wang, Y.-X. Wang and Y. Liu, J. Am. Chem. Soc., 2012, 134, 10244–10250 CrossRef CAS PubMed.
  300. Z.-Q. Li, C.-X. Hu, Y.-Q. Cheng, H. Xu, X.-L. Cao, X.-W. Song, H.-Y. Zhang and Y. Liu, Sci. China: Chem., 2012, 55, 2063–2068 CrossRef CAS.
  301. N. Basilio, A. Pineiro, J. P. Da Silva and L. Garcia-Rio, J. Org. Chem., 2013, 78, 9113–9119 CrossRef CAS PubMed.
  302. Y. Cao, Y.-X. Wang, D.-S. Guo and Y. Liu, Sci. China: Chem., 2013, 57, 371–378 CrossRef.
  303. B.-P. Jiang, D.-S. Guo, Y.-C. Liu, K.-P. Wang and Y. Liu, ACS Nano, 2014, 8, 1609–1618 CrossRef CAS.
  304. Z.-B. Qin, D.-S. Guo, X.-N. Gao and Y. Liu, Soft Matter, 2014, 10, 2253–2263 RSC.
  305. C. Costa, V. Francisco, S. G. Silva, M. L. C. do Vale, L. García-Río and E. F. Marques, Colloids Surf., A, 2015, 480, 71–78 CrossRef CAS.
  306. Y.-X. Wang, Y.-M. Zhang and Y. Liu, J. Am. Chem. Soc., 2015, 137, 4543–4549 CrossRef CAS PubMed.
  307. J. G. Harangozo, V. Wintgens, Z. Miskolczy, J. M. Guigner, C. Amiel and L. Biczok, Langmuir, 2016, 32, 10651–10658 CrossRef CAS PubMed.
  308. Y.-C. Liu, Y.-Y. Wang, H.-W. Tian, Y. Liu and D.-S. Guo, Org. Chem. Front., 2016, 3, 53–61 RSC.
  309. D.-S. Guo, K. Chen, H.-Q. Zhang and Y. Liu, Chem. – Asian J., 2009, 4, 436–445 CrossRef CAS PubMed.
  310. K. Wang, D.-S. Guo and Y. Liu, Chem. – Eur. J., 2010, 16, 8006–8011 CrossRef CAS PubMed.
  311. N. Basilio and L. Garcia-Rio, Chem. – Eur. J., 2009, 15, 9315–9319 CrossRef CAS PubMed.
  312. N. Basilio, M. Martin-Pastor and L. Garcia-Rio, Langmuir, 2012, 28, 6561–6568 CrossRef CAS PubMed.
  313. N. Basilio, B. Gomez, L. Garcia-Rio and V. Francisco, Chem. – Eur. J., 2013, 19, 4570–4576 CrossRef CAS.
  314. N. Basilio, D. A. Spudeit, J. Bastos, L. Scorsin, H. D. Fiedler, F. Nome and L. Garcia-Rio, Phys. Chem. Chem. Phys., 2015, 17, 26378–26385 RSC.
  315. N. Basilio, B. Gomez and L. Garcia-Rio, Langmuir, 2017, 33, 13008–13013 CrossRef CAS PubMed.
  316. C. Bize, J. C. Garrigues, M. Blanzat, I. Rico-Lattes, O. Bistri, B. Colasson and O. Reinaud, Chem. Commun., 2010, 46, 586–588 RSC.
  317. V. Wintgens, C. Le Coeur, C. Amiel, J. M. Guigner, J. G. Harangozo, Z. Miskolczy and L. Biczok, Langmuir, 2013, 29, 7682–7688 CrossRef CAS PubMed.
  318. V. Wintgens, Z. Miskolczy, J. M. Guigner, C. Amiel, J. G. Harangozo and L. Biczok, Langmuir, 2015, 31, 6655–6662 CrossRef CAS PubMed.
  319. V. Wintgens, J. G. Harangozo, Z. Miskolczy, J. M. Guigner, C. Amiel and L. Biczok, Langmuir, 2017, 33, 8052–8061 CrossRef CAS PubMed.
  320. X. Yao, X. Wang, T. Jiang, X. Ma and H. Tian, Langmuir, 2015, 31, 13647–13654 CrossRef CAS.
  321. L. Di Costanzo, S. Geremia, L. Randaccio, R. Purrello, R. Lauceri, D. Sciotto, F. G. Gulino and V. Pavone, Angew. Chem., Int. Ed., 2001, 40, 4245–4247 CrossRef CAS.
  322. H. Huang, D.-M. Li, W. Wang, Y.-C. Chen, K. Khan, S. Song and Y.-S. Zheng, Org. Biomol. Chem., 2012, 10, 729–735 RSC.
  323. D.-S. Guo and Y. Liu, Acc. Chem. Res., 2014, 47, 1925–1934 CrossRef CAS PubMed.
  324. I. S. Ryzhkina, Y. V. Kiseleva, L. I. Murtazina, Y. N. Valitova, S. E. Solov'eva, L. M. Pilishkina and A. I. Konovalov, Russ. Chem. Bull., 2010, 59, 1327–1335 CrossRef CAS.
  325. C.-L. Tu, L.-J. Zhu, P.-P. Li, Y. Chen, Y. Su, D.-Y. Yan, X.-Y. Zhu and G.-Y. Zhou, Chem. Commun., 2011, 47, 6063–6065 RSC.
  326. B. C. M. A. Ashwin, C. Saravanan, M. Senthilkumaran, R. Sumathi, P. Suresh and P. M. Mareeswaran, Supramol. Chem., 2017, 30, 32–41 CrossRef.
  327. R. V. Rodik, A. S. Klymchenko, N. Jain, S. I. Miroshnichenko, L. Richert, V. I. Kalchenko and Y. Mely, Chem. – Eur. J., 2011, 17, 5526–5538 CrossRef CAS.
  328. S. Peng, K. Wang, D.-S. Guo and Y. Liu, Soft Matter, 2015, 11, 290–296 RSC.
  329. J. G. Harangozó, V. Wintgens, Z. Miskolczy, C. Amiel and L. Biczók, Colloid Polym. Sci., 2016, 294, 1807–1814 CrossRef.
  330. K. Wang, D.-S. Guo, M.-Y. Zhao and Y. Liu, Chem. – Eur. J., 2016, 22, 1475–1483 CrossRef CAS.
  331. S. Peng, J. Gao, Y. Liu and D.-S. Guo, Chem. Commun., 2015, 51, 16557–16560 RSC.

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