Synthesis and Characterization of Silicon-Containing Block Copolymers from Nitroxide-Mediated Living Free Radical Polymerization

High etch resistance to oxygen plasma for silicon-containing polymers, and the high thermal and mechanical robustness of the etching product, silicon oxide, make it attractive to design novel silicon-containing block copolymers for direct patterning of nanostructures on a desired substrate. Here, we report the synthesis of a series of block copolymers from silicon-containing styrenic monomers and styrene (St) or 4-acetoxystyrene (AcOSt) using living free radical polymerization via a α -hydride nitroxide-mediated unimer ( α -H unimer). Controlled polymerization with narrow polydispersity (PDI < 1.25) and high yield (up to 80%) were achieved by optimizing polymerization time and temperature, addition of solvents, use of rate accelerants, monomer addition sequence, and solvent polarity. Block copolymer morphologies before and after O 2 plasma were studied using small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). When silicon-containing block formed the major phase and silicon concentration was greater than 12 wt %, the morphology and domain size were maintained after O 2 plasma.