Comparison of zwitterions in amphiphilic PDMS-based surface-modifying polymers for marine fouling-release coatings

Zwitterion-containing polymers can be used as the hydrophilic block in amphiphilic copolymers due to their strong electrostatic interaction with water. Polyethylene glycol (PEG) is commonly used as the hydrophilic block, but PEG experiences rapid autoxidation which limits its lifetime. Alternatively, zwitterions are protein-resistant and have an ultra-low fouling surface that can bind water molecules stronger than PEG. In this study, the successful synthesis of block copolymers of hydrophobic poly(dimethyl siloxane) (PDMS) and four different hydrophilic zwitterionic monomers was carried out. The monomers were also successfully homo-polymerized. The eight polymers based on sulfobetaine methacrylate (SBMA), sulfobetaine methacrylamide (SBMAm), methacrylate phosphocholine (MPC), or carboxybetaine methacrylate (CBMA) were incorporated as a surface-modifying additive into a polyurethane (PU) coating system to investigate the fouling resistance and fouling-release properties of the surfaces. The goal of this study was to determine which zwitterion copolymerized with PDMS produces the best-performing surface for FR purposes. Antifouling (AF) and fouling-release properties were examined through laboratory assays of three common marine fouling organisms: bacteria, algae, and barnacles. Detailed surface characterization was also conducted to investigate the heterogeneity of the surfaces. It was determined that the coatings containing the zwitterionic polymers improved the FR/AF properties compared to the control. The SBMA and CBMA zwitterionic polymers appeared to improve properties the most. For example, the incorporation of the PDMS-SBMA triblock copolymer reduced the barnacle adhesion from 0.58 to 0.19 MPa.

Graphical Abstract