Synthesis, characterization, and intramolecular end-to-end ring closure of α-isopropylidene-1,1-dihydroxymethyl-ω-diethylacetal polystyrene-block-polyisoprene block copolymers

Abstract

Cyclic polystyrene-block-polyisoprenes of controlled dimensions have been synthesized for the first time by the direct coupling of α-isopropylidene-1,1-dihydroxymethyl-ω-diethylacetal- heterodifunctional linear polystyrene-block-polyisoprene precursors previously prepared by living anionic polymerization. Cyclization is achieved under high dilution by intramolecular coupling of the polymer ends under acid catalyst conditions. Using this strategy polystyrene-block-polyisoprene macrocycles of controlled chain dimensions are prepared in high yield (> 90%). Pure cycles were finally recovered by flash chromatography. The synthesis and characterization of both the linear α,ω-heterodifunctional polystyrene-block-polyisoprenes block copolymers precursors and of the corresponding cyclized chain architectures are reported.