Preparation and Low Fouling Property of Amphiphilic Fluorinated Block Copolymers (PEGMA-co-MMA)-b-PC6SMA

ABSTRACT

Compared with traditional biocide-based marine antifouling paints, novel environmentally benign antifouling coatings are designed mainly on surface physico-chemical and bulk materials properties. In particular, advances in nanotechnology and polymer science, and the development of novel surface designs 'bioinspired' by nature, are expected to have a significant impact on the development of a new generation of environmentally friendly marine coatings. Therefore, understanding the correlation between the structure and the properties of the surface of a material and the tuning of appropriate chemical-physical properties at a molecular level may contribute to the development of novel materials for anti-biofouling application.

Among the many environmentally benign coatings, currently in vogue are amphiphilic nanostructured coatings, which incorporate some of the benefits of both hydrophobic and hydrophilic functionalities. Such coatings are designed to create a dynamic surface with local variations in surface chemistry, topography and mechanical properties, i.e., a surface with a compositional, topological, and morphological complexity. In general, the heterogeneous surfaces are created through thermodynamically driven phase segregation, for example, of mutually incompatible block copolymers, followed by cross-linking in situ.

Amphiphilic polymer coatings design may be based on blends of immiscible polymers or contrasting chemistries of block copolymers, which would readily lead to the formation of dynamic surfaces through phase segregation, driven by the chemical incompatibility of the different components. As we all know, fluorinated polymers imbue typical characteristics such as low surface energy, high chemical and thermal resistance and distinct self-assembly behavior. While hydrophilic poly(ethylene glycol) (PEG), which possesses a low polymer¨Cwater interfacial energy, demonstrates excellent resistance to protein adsorption and cell adhesion. Furthermore, poly(ethylene glycol) (PEG) can potentially  possess other desirable properties such as water affinity, low toxicity, high biocompatibility. Thus, in our study, the [N-methyl-perfluorohexane-1-sulfonamide]ethyl methacrylate (C₆SMA) possessing excellent fluoropolymer properties was selected as hydrophobic, fluorinated component, and Poly(ethylene glycol) methyl ether methacrylate (PEGMA) was chosen as hydrophilic component. Therefore the amphiphilic fluorinated block copolymers P(PEGMA-co-MMA)-b-PC₆SMA prepared herein present an opportunity for combining the favorable properties of the fluorinated blocks with those of the P(PEGMA) blocks.

In our study, a series of amphiphilic fluorinated block copolymers P(PEGMA-co-MMA)-b-PC₆SMA consisting of hydrophilic poly(ethylene glycol) methyl ether methacrylate (PEGMA) and hydrophobic fluorinated [N-methyl-perfluorohexane-1-sulfonamide] ethyl methacrylate (C₆SMA) components were successfully prepared by controlled reversible addition fragmentation chain transfer (RAFT) polymerization in solution. The copolymer was characterized by FT-IR, nuclear magnetic resonance proton spectrum (¹H NMR) and gel permeation chromatography (GPC). When the mass content of PEGMA was less than 40%, static contact angle, ¦È, with water and n-hexadecane pointed to the simultaneous hydrophobic and lipophobic character of the films. Dynamic contact angle measurements demonstrated that copolymer film surface underwent reconstruction after contact with water owing to its amphiphilic nature. Consistent with the enrichment of the outer film surface of fluorinated segments, X-ray photoelectron spectroscopy (XPS) measurements proved that a remarkable difference of chemical composition existed between bulk and surface. The atomic force microscopy (AFM) images (tapping mode) revealed distinct microphase segregation structure of nanostructured films. Moreover, our study explored protein adsorption characteristics of the amphiphilic fluorinated copolymer surface through experiments with bovine serum albumin (BSA). Fluorescence microscopy analysis using BSA labelled with fluorescein isothiocyanate (BSA¨CFITC) was performed on the amphiphilic copolymer surface to establish the polymer's protein adsorption resistance. The results proved that amphiphilic fluorinated block copolymer material had an excellent protein adsorption resistance.

Scheme 1. Synthesis of amphiphilic fluorinated diblock copolymer