Synergy effect of bactericidal and antifouling with structure reversion and hydrolysis of cationic amphiphilic copolymer PHMA-b-PCBMAE to zwitterionic copolymer

In this study, cationic amphiphilic copolymers of poly(hexadecyl methacrylate)-b-poly(carboxybetaine meth-acrylate ester) (PHMA-b-PCBMAE) with hydrophobic unit of 100 were synthesized, which can be self-assembled as core-shell nanoparticles with PCBMAE as core and PHMA as shell in chloroform. In response to the change of solvent polarity from chloroform to methanol, the reversion ability of core-shell structure occurred to cationic amphiphilic polymers of PHMA100-b-PCBMAE40, PHMA100-b-PCBMAE50, PHMA100-b-PCBMAE75 and PHMA100- b-PCBMAE100 in an ascending order, which was verified by 1H NMR results. Coatings embedded with the cationic copolymers with PHMA:PCBMAE block ratios of 100:75 and 100:100 showed remarkably decreased water contact angle and protein adsorption amount due to the resulted zwitterionic copolymers upon hydrolysis in aqueous solution. Moreover, dynamic recording of the bactericidal activity against E. coli and S. aureus showed that it took similar to 18 h for the copolymers PHMA100-b-PCBMAE75 and PHMA100-b-PCBMAE100 to take effect in bacteria killing and foulant repelling, and the bacteria left on the coating surfaces were <1.0 % in 24 h. The bactericidal results were in good accord with the trend of the nanoparticle reversion ability, indicating that higher PCBMAE contents of the cationic diblock copolymer facilitated core-shell reversion and subsequent hy-drolysis to zwitterionic copolymer. Moreover, the regenerable surfaces of the coating furtherly ensured the sustainable bactericidal and antifouling activities.

Automated summary

Cationic amphiphilic copolymers were synthesized and self-assembled into core-shell nanoparticles in chloroform. The polarity change of the solvent caused the reversion of the core-shell structure, resulting in zwitterionic copolymers. Coatings embedded with these copolymers showed reduced water contact angle and protein adsorption. The copolymers exhibited bactericidal activity, with less than 1.0% bacteria left on the coating surfaces after 24 hours.