Nitroxide-mediated polymerization of pentafluorostyrene initiated by PS–DEPN through the surface of APTMS modified fumed silica: towards functional nanohybrids

Abstract

Polypentafluorostyrene (PPFS) chains were anchored on the surface of silica nanoparticles (Aerosil A200 fumed silica) by nitroxide-mediated polymerization (NMP) with PS–DEPN as macroinitiator using a “grafting through” strategy with (acryloxypropyl)trimethoxysilane (APTMS)-modified silica. First, NMP of PFS was evaluated with and without silica in various solvents (namely N-methyl-2-pyrrolidone – MP, N,N-dimethylformamide – DMF, and toluene) that favor the dispersion of APTMS-silica in reaction medium. In both situations, polymerization presents all the features of a controlled process whatever the solvent is, with a marked impact of the solvent polarity on the kinetics. Moreover, NMP of PFS is faster in polar solvents when conducted in presence of APTMS-modified silica. By tuning polymerization time and/or solvent polarity, the weight ratio of organic matter to silica can be tuned from 5 to 32 wt%. The impact of such modification rate is demonstrated on the surface properties of SiO₂-PS-b-PPFS deposited on a silicon wafer: indeed, introduction of fluorinated segments in combination with dual roughness (due to inherent dimensions of fumed silica) lead to relevant hydrophobic surface properties with water contact angle as high as (132 ± 1.7)°.