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 methacrylate 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 ∼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 hydrolysis to zwitterionic copolymer. Moreover, the regenerable surfaces of the coating furtherly ensured the sustainable bactericidal and antifouling activities.