Synthesis of a well-defined alternating copolymer of 1,1-diphenylethylene and tert-butyldimethylsilyloxymethyl substituted styrene by anionic copolymerization: toward tailored graft copolymers with controlled side chain densities†
Well-defined alternating copolymers comprising 1,1-diphenylethylene (DPE) and styrene derivatives having sterically bulky tert-butyldimethylsilyloxymethyl groups at the meta position (St-TBS) were successfully synthesized. In the anionic copolymerization of St-TBS and DPE, we found that both the monomer ratio of [DPE]/[St-TBS] (>7-times equiv.) and the bulky TBS functionality efficiently suppressed the formation of a defect structure comprising consecutive styrene–styrene repeating units under appropriate conditions (in THF at 0 °C). In addition, the TBS functionality in the obtained alternating copolymer was easily transformed into hydroxy and benzyl bromide groups. These functional groups could be used as an initiating point for ring-opening polymerization of ε-caprolactone and an introduction point of living polymer anions (polystyrene and poly(methyl methacrylate)), respectively. As a result, the synthesis of side-chain-density-controlled graft copolymers was successfully demonstrated through the grafting “from” and “onto” methods. The obtained alternating copolymers showed a higher glass transition temperature (113 °C) than the corresponding homo poly(St-TBS) (13 °C).