Structural analysis and surface wettability of a novel alternated vinylidene cyanide with fluorinated vinyl ether copolymer

Abstract

The structure, thermal properties and surface wettability of a novel alternating poly(VCN-alt-FAVE8) copolymer based on vinylidene cyanide (VCN) and perfluorooctyl ethyl vinyl ether (FAVE8) were investigated via both temperature-variable wide-angle X-ray powder diffraction (WAXD) and thin-film WAXD using a small angle incidence synchrotron radiation source, differential scanning calorimetry and contact angle measurements, respectively. The results of the WAXD and thin-film WAXD indicated that the alternating copolymer possessed a smectic liquid-crystalline phase at ambient temperature with a couple of fluoroalkyl side chains forming a bilayer with a 3.24 nm spacing and that the fluoroalkyl side chains in a thin-film on a Si wafer align perpendicularly to the surface. The isotropization temperature of the alternating copolymer was 150 °C, which was higher than the 29.5 °C for the poly(FAVE8) homopolymer. The spin-coated poly(VCN-alt-FAVE8) copolymer thin-film yielded high static contact angles for both water and oil similar to those for poly(perfluorooctyl ethyl acrylate), which is known as a superhydrophobic polymer. Dynamic contact angle and X-ray photoelectron spectroscopy measurements in both the dry and hydrated states suggested that the polar cyano and ether groups are enriched at the surface in the wet state, and this reorganization of the surface polar groups caused a large hysteresis of the contact angle. High ordered structure, thermal property and surface wettability of a novel alternated copolymer of vinylidene cyanide and perfluorooctyl ethyl vinyl ether were investigated with wide-angle X-ray diffraction, differential scanning calorimetry, X-ray photoelectron spectroscopy and contact angle measurement. The alternated copolymer showed a smectic liquid crystalline structure and extremely high isotropization temperature of 150 °C, compared with 29.5 °C for the perfluorooctyl ethyl vinyl ether homopolymer. The alternated copolymer also showed large contact angle hysteresis, indicating that surface reorganization of the polar cyano and ether groups occur.