In situ generation of amphiphilic coatings based on a self-catalytic zwitterionic precursor and their antifouling performance

Abstract

Amphiphilic coatings, especially those containing zwitterionic groups, are promising as antifouling coatings. Nevertheless, zwitterion based amphiphilic coatings suffer from poor miscibility between hydrophobic and hydrophilic ingredients. Zwitterionic precursors are good candidates to circumvent this issue, but acid or alkaline water must be used in-situ for the zwitterionic group to be self-generated. The in-situ feature restricts its applicability. The objective of this work focuses on developing a new zwitterionic precursor for easy fabrication of zwitterionic groups containing amphiphilic antifouling coatings. This precursor, i.e., triisopropylsilyl 2-methyl-3-((3-(triethoxysilyl)propyl) amino) propanoate (TMAP), was facile synthesized by one step of aza-Michael addition of (3-aminopropyl) triethoxysilane (APS) and triisopropylsilyl methacrylate. Then further blended with hydroxyl-terminated PDMS (HO-PDMS). The curing behavior, morphology, wetting behavior and the antifouling performance both in lab and field were thoroughly examined for coatings with various amounts of TMAP. It was interesting to find that TMAP could not only be hydrolyzed in-situ into a zwitterionic group via a self-catalytic effect during the curing process, but it also efficiently crosslinked the HO-PDMS under ambient conditions. In contrast to APS, TMAP was also more compatible with HO-PDMS and endowed the coating with relatively homogeneous and a smooth surface after prolonged submersion in artificial seawater. The TMAP-based amphiphilic coatings efficiently mitigated the microfouling in both the laboratory assay and the natural field condition in contrast with common silicone elastomer. Notably, excellent resistance for the macrofouler of the mussel was observed for these coatings, especially for 50 wt% TMAP containing coating with zero settlement.