Cationic Copolymer with Amphiphilic Side Chain and Hydrophobic Siloxane/Polycaprolactone Main Chain for Marine Antifouling Coating

Cationic copolymers formulated with different weight percentages of random copolymerized amphiphilic poly(carboxybetaine methacrylate ester)-poly(methyl methacrylate)-polyvinylpyrrolidone (PCBMAE-PMMA-PVP) side chain and polycaprolactone (PCL)/siloxane main chain were developed via a one-pot continuous reaction for the preparation of marine antifouling coatings. By tuning the weight percentage of the side chain and main chain, a 30% quaternization degree can be achieved without obvious gelation of the cationic copolymer. The hydrolyzable PCBMAE in the side chain and degradable PCL in the main chain led to the self-replenishment of the coating. Moreover, the surface hydrophilicity of the developed coatings was greatly improved owing to the creation of a zwitterionic group during PCBMAE hydrolysis. Results on the weight loss rate of the coating revealed that the amphiphilic side chains, more specifically, the PCBMAE moiety rather than PCL moiety in the hydrophobic main chain, dominated the surface renewal speed. Therefore, the fouling-resistance and fouling-release abilities of the developed cationic copolymer-based coatings were largely promoted compared with the control samples, which only had a main chain. Additionally, experimental results demonstrated that a higher content of amphiphilic side chains correlated with less protein adsorption, but a higher content of siloxane showed more advantages in antibacterial ability. The antibacterial rate of the developed coatings against <i>Escherichia coli</i> and <i>Staphylococcus aureus</i> ranged from 83 to 95%. The marine field test manifested that the optimized coatings can stand the marine biofouling for four months in the thriving growth season of marine microorganisms.