In Situ Probing the Surface Restructuring of Antibiofouling Amphiphilic Polybetaines in Water

Antibiofouling materials have a wide range of applications in biomedical devices and marine coatings. Due to the amphiphilic nature of proteins and organisms, amphiphilic materials have been designed to resist their unspecific adsorption. Surface restructuring behavior of amphiphilic materials in water is believed to play a key role in the antibiofouling mechanisms. In this work, the surface structures of several amphiphilic polybetaine coatings in water have been probed in situ using sum frequency generation (SFG) vibrational spectroscopy. These are novel polybetaines constructed from functionalized polynorbornenes. The polybetaines with oligo(ethylene glycol) (OEG), octyl (C8), or fluorinated (F13) side chains exhibit different surface restructuring behaviors upon contacting water due to their different surface hydrophobicity. The OEG and C8 chains were present and ordered at the water interface, while the F13 chain withdrew from water. The hydrophilic betaine group extended into the water and formed hydrogen bonds with water molecules. The surface restructuring of these materials detected using SFG can be well correlated to their antibiofouling performance, providing an understanding of their antibiofouling mechanisms.