Eco-friendly synthesis of regenerable antimicrobial polymeric resin with N-halamine and quaternary ammonium salt groups

Abstract

An effective macroporous cross-linked antimicrobial polymeric resin containing N-halamine and quaternary ammonium salt moieties was synthesized in an eco-friendly and economical way. Commercially available macroporous crosslinked chloromethylated polystyrene (CMPS) resin reacted with the salt of 5,5-dimethylhydantoin (DMH) and trimethylamine (TMA) in water to produce a polymeric resin containing hydantoinyl and quaternary ammonium salt moieties, poly(p-methylstyrene)-3-(5,5-dimethylhydantoin)-co-trimethyl ammonium chloride (PSHTMA). The hydantoinyl groups in PSHTMA were converted to an antimicrobial N-halamine structure by a facile chlorination reaction in dilute NaOCl solution. The as-synthesized antimicrobial polymeric resin (Cl-PSHTMA) was characterized by FT-IR, X-ray photoelectron spectroscopy, and zeta-potential measurement. The antimicrobial tests showed that the as-synthesized antimicrobial polymeric resin was capable of 7-log inactivation of S. aureus and 8-log inactivation of E. coli within 1 minute contact time. Moreover, the N-halamine moieties in Cl-PSHTMA exhibited excellent regenerability.

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Introduction

Microbial contamination remains one of the most serious problems in several areas, particularly in water purification systems.^1,2 Common disinfectants used in the treatment of water are free halogen, ozone, and chlorine dioxide. However, these soluble disinfectants suffer from some disadvantages such as instability in water and reactivity with organic impurities in water to form undesired byproducts.^3–6 As a result, the development of insoluble polymeric antimicrobial materials as disinfectants is desirable. Recently, extensive research has been reported on antimicrobial polymers including polymeric quaternary ammonium salts (poly-quats),^7,8 polymeric quaternary phosphonium salts,^9–12 polymers containing halogenated sulphonamide groups,^13–16 and N-halamine polymers.^17–26 Among them, polymeric N-halamines are excellent disinfectants for several reasons including super antimicrobial efficacies, broad antimicrobial spectra, regenerabilities, lack of corrosion of surfaces, low toxicities, and relatively low expense.

Worley and co-workers have focused on the development of novel polymeric N-halamines for use in water disinfection since the early 1990s. They first developed water-insoluble N-halogenated polystyrenehydantoins, poly[1,3-dichloro-5-methyl-5-(4-vinylphenyl)hydantoin] (poly1-Cl) and poly[1,3-dibromo-5-methyl-5-(4-vinyl-phenyl)hydantoin] (poly1-Br) by Friedel–Crafts acylation, cyclization, and halogenation.^17–21 It was found that these polymeric N-halamine powders could inactivate numerous species of bacteria, fungi, and even rotavirus in only seconds of contact time in flowing water. However, when these polymeric N-halamine powders were filled in cartridge for disinfection of water, water could not easily pass through it without external pressure. To solve this issue, Worley group developed macroporous cross-linked poly1-Cl and poly1-Br beads which were suitable for the disinfection of drinking water in a cartridge filter.^22,23 Encouragingly, poly1-Br beads have been commercially used for disinfection of drinking water in developing countries such as India, China, and Brazil. However, in its production, large quantities of waste organic solvent and waste water containing high concentrations of cyanide and aluminum ions were produced. Thus, new macroporous cross-linked halogenated methylated polystyrene hydantoin beads (PHY-Cl and PHY-Br) were synthesized by dehydrochlorination between the macroporous crosslinked CMPS resin and DMH and then halogenation of amide nitrogen in the hydantoinyl ring.²⁴ However, this dehydrochlorination can only undergo in few organic solvents such as N,N-dimethylformamide (DMF) and under high temperature due to hydrophobic CMPS and hydrophilic DMH.

In this study, we designed an eco-friendly and economical route to synthesize a macroporous cross-linked antimicrobial polymeric resin containing N-halamine and quaternary ammonium salt moieties, Cl-PSHTMA. The synthetic route for Cl-PSHTMA is shown in Scheme 1. Macroporous crosslinked CMPS resin can react easily with the salt of DMH and TMA in water to produce PSHTMA resin containing hydantoinyl and quaternary ammonium salt moieties. Upon chlorination with sodium hypochlorite solution, PSHTMA was transformed into Cl-PSHTMA. Very interestingly, only water was used as solvent in the whole synthetic process. Also, the mild reaction temperature and short reaction time can save energy and enhance productivity. Apparently, this two-step synthetic reaction could be easily enlarged for industrial application. It is well known that the surfaces of bacterial cells are usually negatively charged. So, antibacterial polymers with positive charges in their surfaces can easily hold the bacteria and then effectively kill them. Moreover, the presence of quaternary ammonium salt moieties in the surface of the resin can enhance its hydrophilicity and swelling capacity in water, which may increase its disinfection efficacy.

Scheme 1 Synthesis of Cl-PSHTMA.

Results and discussions

Grafting DMH and TMA onto CMPS to prepare PSHTMA

CMPS resin has been widely used as starting material to synthesize various kinds of resins for water treatment due to its active chloromethylated groups.²⁷ It has been reported that macroporous cross-linked CMPS resin could react with DMH to form a polymeric N-halamine precursor.²⁴ However, the suitable solvent for this reaction is DMF due to the huge difference in the hydrophilicity of CMPS and DMH. In order to avoid the use of organic solvents, lower reaction temperature to save energy, shorten reaction time to increase production efficiency, we adopted a one-pot method to simultaneously graft DMH and TMA onto macroporous cross-linked CMPS resin in water to prepare PSHTMA resin. We think that the attachment of quaternary ammonium salt moieties can enhance the surface hydrophilicity of the resin, which makes DMH easily grafted onto the resin in water.

For evaluation of the effect of reaction temperature on grafting reaction, the molar ratio of DMH and TMA was kept as 1 : 1 (the total moles of DMH and TMA added were equal to the moles of active chloromethylated groups). The grafting reaction was carried out for 8 h at different temperatures in water. The weight gain percentages of PSHTMA resin under different temperatures were shown in Fig. 1. It was found that the weight gain percentages of resin increased with the increase of temperatures from 20 to 60 °C. However, when the temperatures were higher than 60 °C, the weight gain percentages of resin kept almost constant. It is clear that 60 °C is suitable temperature for this grafting reaction.

Fig. 1 Effect of reaction temperature on grafting DMH and TMA onto CMPS. The molar ratio of DMH and TMA was 1 : 1 (the total moles of DMH and TMA added were equal to the moles of active chloromethylated groups in CMPS); solvent: water; reaction time: 8 h.

For evaluation of the effect of reaction time on grafting reaction, the grafting reaction was carried out for different times at 60 °C in water. The weight gain percentages of PSHTMA resin under different reaction times were shown in Fig. 2. As shown in Fig. 2, the weight gain percentages of resin increased dramatically within 1 h (wg% = 29.13% after 1 h), and then tardily to the maximum in the next 3 h. Thus, a reaction time of 4 h was required.

Fig. 2 Effect of reaction time on grafting DMH and TMA onto CMPS. The molar ratio of DMH and TMA was 1 : 1 (the total moles of DMH and TMA added were equal to the moles of active chloromethylated groups in CMPS); solvent: water; reaction temperature: 60 °C.

Although the quaternary ammonium salt structure formed by grafting TMA onto CMPS rein could promote the grafting process of DMH onto CMPS resin, too much consumption of active chloromethylated sites in CMPS resin by TMA molecules would decrease the reaction chance between CMPS resin and DMH molecules. In order to obtain higher DMH loading in the resin, we tried to find the optimal molar ratio of DMH and TMA added during grafting process. The results were shown in Fig. 3. The experiments showed that TMA could react with CMPS resin completely if the moles of TMA added were less than those of active chloromethylated moieties in CMPS. Thus, the weight gain percentages of the resin attributed to TMA could be calculated according to the consumed TMA moles and the weight gain percentages of the resin attributed to DMH should be the difference between the total weight gain percentages of the resin and the weight gain percentages of the resin attributed to TMA. As shown in Fig. 3, when the molar ratio of DMH and TMA added was 2 : 1, the weight gain percentage of resin attributed to DMH reached its maximum (19.62%).

Fig. 3 The total weight gain percentages of the resin and the weight gain percentages of the resin attributed to DMH under different molar ratios of DMH and TMA. Solvent: water; reaction temperature: 60 °C; reaction time: 4 h; the total moles of DMH and TMA added were equal to the moles of active chloromethylated groups in CMPS.

Chlorination of PSHTMA

The amide groups in the hydantoinyl rings of PSHTMA resin can be transformed to N-halamine functional groups upon exposure to dilute sodium hypochlorite solution. In this study, the effect of chlorination time on the percentage of oxidative chlorine (Cl⁺%) in Cl-PSHTMA resin was tested (the molar ratio of NaOCl and DMH grafted onto resin was 1 : 1). As shown in Fig. 4. The Cl⁺% in Cl-PSHTMA resin increased promptly to 3.23% after the first 15 min, and then to 4.65% after 2 h. Then, with the longer chlorination times, the Cl⁺% in Cl-PSHTMA resin did not increase any more. The results showed that the chlorination of PSHTMA could be finished within 2 h.

Fig. 4 Effect of chlorination time on the percentage of oxidative chlorine (Cl⁺%) in Cl-PSHTMA resin.

Characterization of the as-prepared PSHTMA and Cl-PSHTMA

FT-IR spectra. FTIR spectra were recorded and used to conform the effective grafting of DMH onto macroporous cross-linked CMPS resin. As shown in Fig. 5, for macroporous cross-linked CMPS resin, the bands at 1265 and 674 cm⁻¹ are attributed to symmetric and antisymmetric stretching vibrations of CH₂–Cl.^27,28 For PSHTMA resin, the characteristic peaks of CH₂–Cl became very weak due to the grafting of DMH and TMA onto CMPS, and two new bands at 1771 and 1708 cm⁻¹ are ascribed to the C=O stretching vibrations on the hydantoinyl ring of PSHTMA.²⁹

Fig. 5 FT-IR spectra of CMPS and PSHTMA.

XPS spectra. The chemical changes occurred on resin surfaces after grafting and chlorinating reaction were further explored by X-ray photoelectron spectroscopy (XPS) analysis. The XPS wide scan spectra of CMPS, PSHTMA, and Cl-PSHTMA are shown in Fig. 6. In the case of CMPS, the appearance of a Cl 2p signal at a binding energy of 200 eV verifies the existence of chlorine in CMPS.³⁰ In the case of PSHTMA, the Cl 2p signal became much weak, which is mainly ascribed to the successful grafting reaction between DMH and –CH₂Cl group of CMPS. Also, the appearance of a new N 1s peak appeared at 400 eV indicates that DMH and TMA were successfully grafted onto CMPS. In the case of Cl-PSHTMA, the Cl 2p signal was stronger than that of PSHTMA, indicating that chlorination caused the increase of chlorine content.

Fig. 6 XPS wide scan spectra of CMPS, PSHTMA and Cl-PSHTMA (Cl⁺% = 5.11%).

The N 1s core-level spectra of Cl-PSHTMA, PSHTMA, and CMPS between 395 and 407 eV were shown in Fig. 7. For the N 1s core-level spectrum of CMPS shown in Fig. 7c, no prominent peaks were found as there was no nitrogen element in CMPS resin. The N 1s core-level spectrum of PSHTMA resin can be curve-fitted into three peak components with binding energies (BEs) at about 399.9, 400.7, and 402.6 eV (Fig. 7b). The peak components at about 399.9 and 400.7 eV are attributed to the covalently bonded imide nitrogen (–N<) and amide nitrogen (>NH) in hydantoinyl rings. The peak component at about 402.6 eV is caused by the positively charged nitrogens (N⁺) species in quaternary ammonium salt moieties.^30–33 The N 1s core-level spectrum of Cl-PSHTMA is very similar to that of PSHTMA, indicating that chlorination has no effect on quaternary ammonium salt moieties. Fig. 7d–f showed the Cl 2p core-level spectra of Cl-PSHTMA, PSHTMA, and CMPS resins. For CMPS resin (Fig. 7f), The peak components of the Cl 2p_3/2 and Cl 2p_1/2 doublet at the BEs of about 200.1 and 201.6 eV are attributable to the covalently bonded chlorine in the chloromethylated group (CH₂–Cl).³⁰ For PSHTMA resin (Fig. 7e), an additional peak at 197.3 eV is attributable to anionic chlorine species (Cl⁻) due to the quaternarization between TMA and CMPS,^30,34 and the disappearance of two peaks at about 200.1 and 201.6 eV results from the consumption of active covalent chlorine in CH₂–Cl of CMPS during grafting reaction. For Cl-PSHTMA resin (Fig. 7d), the new peak at about 200.4 eV is attributable to the covalently bonded chlorine on the amide nitrogen of hydantoinyl ring (Cl–N) caused by chlorination.

Fig. 7 N 1s core-level spectra of (a) Cl-PSHTMA (Cl⁺% = 5.11%), (b) PSHTMA, (c) CMPS and Cl 2p core-level spectra of (d) Cl-PSHTMA (Cl⁺% = 5.11%), (e) PSHTMA, (f) CMPS.

Zeta potentials. To further elucidate the immobilization of TMA onto CMPS, zeta-potential analyses of the resins were performed in water. As shown in Fig. 8, the zeta potential of CMPS resin showed a negative value (−26.8 mV). In the case of PSHTMA resin, the zeta-potential value was 55.7 mV, indicating that quaternary ammonium salt structure was formed after grafting TMA onto CMPS. The zeta-potential value of Cl-PSHTMA was 51.3 mV, suggesting that chlorination did not damage the quaternary ammonium salt structure.

Fig. 8 The zeta potential of (a) CMPS, (b) PSHTMA, and (c) Cl-PSHTMA (Cl⁺% = 5.11%).

Surface area, particle size and pore volume

The Brunauer–Emmett–Teller (BET) surface areas and pore volumes of CMPS and PSHTMA were determined from the N₂ adsorption–desorption isotherms, whereas their pore size distributions of the adsorbents were measured by the Barrett–Joyner–Halenda model. As shown in Fig. 9, these two isotherms had the characteristic feature of the type IV isotherm with almost the same inflection points and hysteresis loops,³⁵ indicating that the pore shapes of CMPS and PSHTMA resins were similar. It means that the pores in CMPS resin had not been destroyed significantly during the grafting reaction. Also, abrupt increases in nitrogen volumes adsorbed at higher P/P₀ suggested a quite large contribution in mesopore and macropore range in both CMPS and PSHTMA resins. By comparing the isotherm of CMPS with that of PSHTMA, we found that the nitrogen volumes adsorbed by PSHTMA were smaller than those adsorbed by CMPS, indicating a lower porosity for PSHTMA resin. Meanwhile, analysis of the low-pressure nitrogen adsorption data indicated that the pore size distributions within these two resins were strongly biased towards sub-nanometer. The porous structure parameters of CMPS and PSHTMA resins were listed in Table 1. The small decreases of surface area, pore size, and pore volume could be ascribed to the successful grafting of DMH and TMA onto the inner surface of the resin.

Fig. 9 Nitrogen adsorption–desorption isotherms and pore size distribution curves of CMPS and PSHTMA resins.

Table 1 Surface area, pore size and pore volume of CMPS, and PSHTMA resins

	Surface area (m^2 g^−1)	Pore size (nm)	Pore volume (cm^3 g^−1)
CMPS	35.71 ± 1.28	4.61 ± 0.19	0.08 ± 0.004
PSHTMA	25.37 ± 1.06	4.47 ± 0.17	0.06 ± 0.004

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Antimicrobial efficacies of the as-prepared Cl-PSHTMA

The antimicrobial efficacies of the as-prepared Cl-PSHTMA resin were tested by challenging with Gram-positive Staphylococcus aureus ATCC 6538P (S. aureus) and Gram-negative Escherichia coli O157:H7 ATCC 11229 (E. coli O157:H7). The testing results for CMPS as the first control, PSHTMA as the second control, and Cl-PSHTMA were summarized in Table 2. As can be seen from Table 2, Cl-PSHTMA resin provided a 7.26 log reduction of S. aureus and a 8.26 log reduction of E. coli O157:H7 in a contact time of less than or equal to 1 min. The super powerful antimicrobial efficacies of Cl-PSHTMA resin are probably due to synergistic enhancement of quaternary ammonium salt and N-halamine functional groups. For CMPS resin, the log reductions of S. aureus and E. coli O157:H7 are 0.18 and 0.28 with a contact time of 1 min, 0.17 and 0.15 with a contact time of 5 min, 0.23 and 0.24 with a contact time of 10 min, respectively. For PSHTMA resin, the log reductions of S. aureus and E. coli O157:H7 are 0.45 and 0.07 with a contact time of 1 min, 0.44 and 0.27 with a contact time of 5 min, 0.52 and 0.09 with a contact time of 10 min, respectively. These small log reductions are possibly due to the adsorption of bacteria on the surface of the resins.^22,24

Table 2 Antimicrobial efficacies against S. aureus and E. coli O157:H7 for CMPS, PSHTMA, and Cl-PSHTMA

	Contact time (min)	log reduction of S. aureus^a	log reduction of E. coli O157:H7^b
a The concentration of the bacteria was 1.80 × 10^7 CFU mL^−1.b The concentration of the bacteria was 1.82 × 10^8 CFU mL^−1.c The first control sample.d The second control sample.e A Cl^+ loading of 5.04%.
CMPS^c	1	0.18	0.38
	5	0.17	0.15
	10	0.23	0.24
PSHTMA^d	1	0.45	0.07
	5	0.44	0.27
	10	0.52	0.09
Cl-PSHTMA^e	1	7.26	8.26
	5	7.26	8.26
	10	7.26	8.26

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Regenerability of the as-prepared Cl-PSHTMA resin

For regenerability evaluation of Cl-PSHTMA resin, 5.00 g of Cl-PSHTMA resin containing 5.11 wt% of Cl⁺ was first treated with 150 mL of 0.03 N Na₂S₂O₃ to quench the oxidative chlorine and then rechlorinated with 13.57 g of 10% NaClO solution at ice-bath temperature. After 10 cycles of the quenching-rechlorination treatment, the Cl⁺% of Cl-PSHTMA resin was almost the same as the original value, indicating that the antimicrobial N-halamine functional groups of Cl-PSHTMA resin had excellent regenerability by a simple rechlorination (see Fig. 10).

Fig. 10 Regenerability of Cl-PSHTMA.

Experiment

Chemicals and reagents

The macroporous crosslinked chloromethylated polystyrene resin (CMPS, cross-linked with 5.60% DVB, 21.00% chlorine, diameter: 0.5–0.8 mm) was purchased from Suqing Group (Jiangyin, Jiangsu, China). 5,5-Dimethylhydantoin was purchased from Shanghai Yinghan Chemical Co., Ltd. The bacteria employed were Staphylococcus aureus ATCC 6538P and Escherichia coli O157:H7 ATCC 11229 (Shanghai Institute of Materia Medica of the Chinese Academy of Sciences). The Trypticase soy agar used was from Sinopharm Chemical Reagent. Co., Ltd. Sodium carbonate was purchased from Jiangsu Qiangsheng Chemical Co., Ltd. Other chemicals and solvents were purchased from Aladdin Chemical Company.

Instruments

The IR spectra were carried out on Mattson PK-60000 infrared spectrometer (KBr pellets). The surface of polymeric resins was analyzed using X-ray photoelectron spectroscopy (XPS) on a Perkin Elmer PHI 5000 ESCT System. Specific surface area (BET) data were obtained using Nova 4000e Surface Area and Pore Size Analyzer. The zeta-potential was measured by a Zetasizer Nano ZS90.

Preparation of poly(p-methylstyrene)-3-(5,5-dimethylhydantoin)-co-trimethyl ammonium chloride (PSHTMA)

PSHTMA was prepared by a one-pot method. For example, 1.4208 g of DMH (0.0111 mol) and 1.1766 g of Na₂CO₃ (0.0111 mol) were added to 30 mL of deionized water in a 250 mL flask and stirred until completely dissolved. Then 2.8200 g of CMPS was added to the solution above. The mixture was stirred slowly at 60 °C while 1.1013 g of 30% trimethylamine solution (0.0056 mol) was added dropwise. After 4 h, the produced PSHTMA resin was removed by filtration and washed with tap water for 6 times and then deionized water once. After dried in a vacuum oven at 80 °C for 2 h, 3.6719 g of PSHTMA resin was obtained. The diameter of PSHTMA resin is 0.8–1.5 mm. According to the weight gain of the resin attributed to DMH, the conversion rate of DMH was calculated to be 54.05% and the relative ratio (n/m) was calculated to be ∼1 : 1. The weight gain percentage (wg%) of the resin could be calculated using the following equations:

wg% = (W₂ − W₁)/W₁ × 100% (1)

where W₁ and W₂ are the weights in grams of CMPS and the produced PSHTMA, respectively.

Chlorination and titration

2.00 g of PSHTMA resin were suspended in 20 mL of deionized water. To the stirred suspension were added dropwise 3.42 g of 10% sodium hypochlorite solution at 0–5 °C over a period of 2 h (the molar ratio of NaOCl and DMH grafted onto resin was 2 : 1). Meanwhile, the pH was adjusted to 7 by the addition of 0.5 N HCl solution. The chlorinated resin (Cl-PSHTMA) was then filtered, rinsed with tap water, and then thoroughly rinsed with deionized water to remove free chlorine, and then dried at 45 °C for 2 h. The diameter of Cl-PSHTMA resin is 0.8–1.5 mm. Regeneration of the antimicrobial function of the sample resin was performed under the same conditions.

The oxidative chlorine loading of the as-prepared Cl-PSHTMA resin was determined by a modified iodometric/thiosulfate titration procedure. About 0.04 g of the chlorinated resin powder was suspended in 45 mL of ethanol. After addition of 0.20 g of KI and 5 mL 0.04 N sulfuric acid solution, the solution was titrated with 0.01 N of sodium thiosulfate solution until the yellow color disappeared at the end point. The percentage of Cl⁺ in the chlorinated resin could then be calculated using the following equations:

Cl⁺% = [N × V × 35.45/(2 × W)] × 100% (2)

where N and V are the normality (equiv. L⁻¹) and volume (L), respectively, of the Na₂S₂O₃ consumed in the titration, and W is the weight in grams of the chlorinated samples.

Assessment of antimicrobial efficacy

The Cl-PSHTMA resin prepared as described above with a chlorine loading of about 5.04% was tested for antimicrobial efficacy against Staphylococcus aureus ATCC 6538P and Escherichia coli O157:H7 ATCC 11229. 0.75 g of chlorinated resin (Cl-PSHTMA) was added to 75 mL of bacterial suspension containing 10⁷ to 10⁸ CFU mL⁻¹ buffered at pH = 7 in a 250 mL conical flask. After concussion with 200 r min⁻¹ at 37 °C for 1, 5, and 10 min, 0.5 mL of the various bacterial suspensions were placed in sterile test tubes, each containing 4.0 mL of sterile phosphate buffer and 0.5 mL of sterile 0.1 N sodium thiosulfate to quench any oxidative free chlorine which might have been present, and vortexed for several seconds. The mixed bacterial suspensions were serially diluted, and 100 μL of each dilution was placed onto a nutrient agar plate. The same procedure was applied to both CMPS and PSHTMA resins as controls. Viable bacterial colonies on the agar plates were counted after incubation at 37 °C for 24 h. Bacterial reduction is reported according to the following equation:

log reduction of bacteria = log(N₁/N₂) (3)

where N₁ is the number of bacteria counted from the original bacterial suspension, and N₂ is the number of bacteria counted from each sample.

Regenerability testing

Cl-PSHTMA resin was tested for its regenerability. 5.00 g of Cl-PSHTMA resin containing an oxidative chlorine loading of 5.11% was subjected to 150 mL of 0.03 N Na₂S₂O₃ solution for 1 h to quench the oxidative chlorine completely, and then regenerated by exposure to 13.57 g of 10% sodium hypochlorite for 2 h after rinsing with distilled water to remove the adsorbed Na₂S₂O₃. After each cycle, the Cl⁺% of the sample was measured for the evaluation of regenerability.

Conclusions

In summary, we have developed an eco-friendly and economical technique to synthesize a high-efficacy macroporous cross-linked antimicrobial polymeric resin containing both N-halamine and quaternary ammonium salt moieties. Very interesting, all starting materials, macroporous crosslinked CMPS, DMH, TMA, and NaOCl solution can be produced at industrial scales of thousands of tons; the used solvent is “green” water; the reaction temperature is mild and reaction time is short. More importantly, this technique can be easily scaled up without the use of specific equipments and the production cost is low. The as-prepared Cl-PSHTMA resin exhibited excellent antimicrobial efficacies against S. aureus and E. coli O157:H7. The existence of quaternary ammonium salt groups improves the surface hydrophilicity of Cl-PSHTMA resin, which may increase utilization efficiency of oxidative halogens bonded to amide nitrogens of hydantionyl rings during disinfection of water. Cl-PSHTMA resin can be reused many times due to its excellent regenerability. With the high antimicrobial efficacy and the excellent regenerability, the as-prepared Cl-PSHTMA resin is expected to have potential commercial applications in the water disinfection.

Acknowledgements

The authors would like to acknowledge the financial support from Shanghai Pujiang Talent Project (11PJ1407600), the Research and Innovation Project of Municipal Education Commission of Shanghai (12YZ085), and the Shanghai Natural Science Foundation (10ZR1407700). This work is supported by PCSIRT (RT1269), the Program of Shanghai Normal University (DZL124).

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Footnote

† Electronic supplementary information (ESI) available. See DOI: 10.1039/c3ra47147k

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