A General Approach to Controlling the Surface Composition of Poly(ethylene oxide)-Based Block Copolymers for Antifouling Coatings

Abstract

To control the surface properties of a polystyrene-block-poly(ethylene oxide) diblock copolymer, perfluorinated chemical moieties were specifically incorporated into the block copolymer backbone. A polystyrene-block-poly[(ethylene oxide)-stat-(allyl glycidyl ether)] [PS-b-P(EO-stat-AGE)] statistical diblock terpolymer was synthesized with varying incorporations of allyl glycidyl ether (AGE) in the poly(ethylene oxide) block from 0 to 17 mol %. The pendant alkenes of the AGE repeat units were subsequently functionalized by thiol-ene chemistry with 1H,1H,2H,2H-perfluorooctanethiol, yielding fluorocarbon-functionalized AGE (fAGE) repeat units. (1)H NMR spectroscopy and size-exclusion chromatography indicated well-defined structures with complete functionalization of the pendant alkenes. The surfaces of the polymer films were characterized after spray coating by X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure spectroscopy (NEXAFS), showing that the P(EO-stat-fAGE) block starts to compete with polystyrene to populate the surface after only 1 mol % incorporation of fAGE. Increasing the incorporation of fAGE led to an increased amount of perfluorocarbons on the surface and a decrease in the concentration of PS. At a fAGE incorporation of 8 mol %, PS was not detected at the surface, as measured by NEXAFS spectroscopy. Water contact angles measured by the captive-air-bubble technique showed the underwater surfaces to be dynamic, with advancing and receding contact angles varying by >20°. Protein adsorption studies demonstrated that the fluorinated surfaces effectively prevent nonspecific binding of proteins relative to an unmodified PS-b-PEO diblock copolymer. In biological systems, settlement of spores of the green macroalga Ulva was significantly lower for the fAGE-incorporated polymers compared to the unmodified diblock and a polydimethylsiloxane elastomer standard. Furthermore, the attachment strength of sporelings (young plants) of Ulva was also reduced for the fAGE-containing polymers, affirming their potential as fouling-release coatings.

Monodisperse Cylindrical Micelles and Block Comicelles of Controlled Length in Aqueous Media

“…In fact, it has been shown that the allyl groups on PAGE backbone can be readily modified with biologically-relevant molecules of interest via thiol-ene radical coupling. 65 Based on these features, PAGE-based materials have recently been used for hydrogel formation, 66 nanopatterning biomolecules, 67 drug delivery, [68][69][70] and lithium batteries. 71 In our approach, PFS56-b-PAGE156 was first synthesized as an intermediate target.…”

Block Copolymer Membranes for Aqueous Solution Applications

“…Cho et al 29 synthesized amphiphilic copolymers with side chains of hydrophilic PEO blocks and hydrophobic blocks of polystyrene (PS) and polyisoprene (PI) with clear decrease of the number of attached microalga and diatom cells as the PEO content of increased. A similar approach using ethoxylated fluoroalkyl side chains were previously used with success 30,31 . Copolymers with zwitterionic segments have been explored by other groups.…”

Molecular level studies of polymer behaviors at the water interface using sum frequency generation vibrational spectroscopy

“…However, this technique requires intense tunable X-rays and for this reason must be performed at synchrotrons. [38][39][40] Arguably, one of the most influential analytical techniques in the polymer/water interface research field is the relatively new spectroscopic tool, sum frequency generation (SFG) vibrational spectroscopy. This technique allows researchers to study molecular vibrations in real time and in situ only where centrosymmetry is broken and therefore solely focuses on the water/polymer structured interface, unlike other techniques.…”