Core functionalization of semi-crystalline polymeric cylindrical nanoparticles using photo-initiated thiol–ene radical reactions

Functionalisation by radical thiol–ene addition of a cylindrical micelle formed by crystallisation-driven self-assembly is demonstrated.

Instrumentations 1 H Nuclear magnetic resonance ( 1 H NMR) spectra were recorded on a Bruker spectrometer operating at a frequency of 400 MHz in CDCl 3 (unless stated otherwise). The chemical shifts are given in ppm with tetramethylsilane (TMS) as an internal reference.
Size exclusion chromatography (SEC) was performed on an Agilent 1260 Infinity Multi-Detector SEC instrument equipped with refractive index and UV detectors with CHCl 3 and 0.5% triethylamine as eluent at a flow rate of 1 mL/min. SEC data was calibrated by Cirrus GPC software with PS standards.
Differential scanning calorimetry (DSC) analysis was performed using a Mettler Toledo DSC1 star system. Samples were run at a heating or cooling ramp of 10 °C·min -1 in triplicate in series under a nitrogen atmosphere in 40 μL aluminum crucibles. T g and T m of various samples were obtained in the first runs.
The stained transmission electron microscopy (TEM) images were obtained by using a JEOL 2000FX instrument operated at 200 kV. TEM samples were negatively stained by phosphotungstic acid (PTA, Electronic Supplementary Material (ESI) for Polymer Chemistry. This journal is © The Royal Society of Chemistry 2016 S2 2 wt%) or uranyl acetate (UA, 2.5 wt%) on formvar/carbon grids (300 Mesh, Cu, Elektron Technology UK LTD). Typically, formvar/carbon grids were cleaned by air plasma from a glow-discharge system (2 min, 20 mA) which also improved the hydrophilicity of the grids. 20 µL of particle solution (0.25 mg/mL) was added onto the grid and the solution was blotted away after 2 min and then left to airdry. 5 µL of a 2 wt% PTA solution was then added onto the grid to stain the particles and was blotted away after 30 s before air-drying.
TEM images on graphene oxide (GO) support were also obtained using a JEOL 2000FX instrument operated at 200 kV. The GO grids were prepared as follows: lacey carbon grids (400 Mesh, Cu, Elektron Technology UK LTD) were cleaned by air plasma from a glow-discharge system (2 min, 20 mA) to improve the hydrophilicity of the lacey carbon. One drop of GO solution (0.10 -0.15 mg·mL -1 ) was deposited on each grid and left to air-dry totally. Then one drop of the sample solution (20 µL) was added onto a GO grid and after 2 min, the solution was blotted away before drying totally.
The hydrodynamic diameter (D h ) of nanoparticles was determined by dynamic light scattering (DLS). Typically, scattering of a 0.25 mg·mL -1 aqueous nanoparticle solution was measured with a Malvern Zetasizer NanoS instrument equipped with a 4 mW He-Ne 633 nm laser module at 25 °C. Measurements were carried out at a detection angle of 173° (back scattering) and the data was further analyzed by Malvern DTS 6.20 software. D h was calculated by fitting the apparent diffusion coefficient in the Stokes-Einstein equation D h = kT/(3πηD app ), where k is the Boltzmann constant, T is the temperature and η is the viscosity of the solvent. D h only coincides to the real hydrodynamic diameter when the measured sample is a solution of monodispersed spherical particles as D app equals the translational diffusion (D t ). For cylindrical particles, owing to their anisotropy, the rotational diffusion is not negligible and contributes to the D app . Therefore, the D h measured for the cylindrical micelles only has a relative value and provides dispersity information to detect multiple populations.
WAXD was performed on a Panalytical X'Pert Pro MPD equipped with a CuKα 1 hybrid monochromator as the incident beam optics. Generally, ca. 30 mg of self-assembled freeze-dried particles were placed in a 10 mm sample holder, and standard "powder" 2θ -θ diffraction scans were carried out in the angular range from 2θ 10° to 30° at room temperature.
Photo-initiated thiol-ene radical reactions were carried out in a Metalight QX1 light box equipped with 12 × 9 W bulbs with a peak output at 365 nm for 1 h. Typically, samples were placed 10 cm away from the source with the bulbs arranged concentrically around them.

Crystallization-driven self-assembly of PLLA-b-PMAC-b-PTHPA triblock copolymer, 4
The self-assembly of PLLA-b-PMAC-b-PTHPA triblock copolymer, 4, was performed by a solvent evaporation method. Typically, 0.5 mL of THF and 2 mL of water (v THF : v H2O = 20 : 80) were added to 50 mg of polymer inside a vial. Acetic acid (1 eq. to each PTHPA block) was also added to the mixture to facilitate the hydrolysis of THPA. The vial was sealed with a needle inserted through the seal and the mixture was allowed to stir at 55 °C for 30 h before being quenched by cooling in liquid nitrogen and subsequent lyophilization. The freeze-dried nanoparticles were then dissolved directly into 18.2 MΩ·cm water (0.25 mg/mL) for TEM and DLS analysis.

Functionalization of PLLA-b-PMAC-b-PAA triblock copolymers using photo-initiated thiol-ene radical reactions
Firstly, the precursor PLLA-b-PMAC-b-PTHPA triblock copolymer was added to a mixture of 1,4dioxane and H 2 O (2 mL and 0.5 mL respectively) with a further addition of acetic acid (3 eq. to each PTHPA block). The mixture was then sealed in a vial and heated at 65 °C to deprotect the PTHPA block. After 12 h, full deprotection was achieved as confirmed by 1 H NMR spectroscopy analysis. The mixture was precipitated in n-hexane three times and dried in vacuo. Benzyl mercaptan (10 eq. to each allyl group) and 2-benzyl-2-(dimethylamino)-4'-morpholinobutyrophenone UV initiator (0.5 eq. to each allyl group) were then added to PLLA-b-PMAC-b-PAA triblock copolymers (25 mg) in 1,4-dioxane (0.5 mL). The mixture was exposed to UV irradiation for 1 h before being precipitated in n-hexane three times and dried in vacuo. 1 H NMR (400 MHz, d 6 -DMSO, ppm, Figure S7