Polyfluoroalkyl siloxanes with varying trifluoropropyl content: Synthesis, characterization and solvent resistance studies

Abstract

This paper describes the synthesis of vinyl terminated poly(dimethyl-co-methyltrifluoropropyl) siloxane with varying 3,3,3-trifluoropropyl (TFP) content via anionic ring opening copolymerization (AROP) of cyclic oligomers, octamethylcyclotetrasiloxane (D4) and 1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane (F3). The copolymers were characterized in detail by FTIR and NMR (1H, 13C, 29Si & 19F nuclei) spectroscopy techniques. Polymers were cured via platinum catalysed hydrosilylation to form crosslinked networks containing different proportions of fluorine. As evidenced from XRD, higher TFP content in the copolymer reduced the crystallinity of the polymer. Compounded polymers were evaluated for dynamic mechanical properties by DMA: positive shift in Tg from −110 °C to −62 °C was observed with increase in TFP content. Swelling studies in different hydrocarbon solvents of varying chain lengths proved the influence of TFP groups in imparting solvent resistance. Hydrophobicity of copolymers increased by 13% with increase in TFP content from 0% to 64.2%, as evidenced from contact angle measurements.