RAFT polymerization of an aromatic organoborane for block copolymer synthesis

Abstract

Synthesizing polystyrene-block-poly(vinyl alcohol) (PS-b-PVA) via controlled radical polymerization of vinyl acetate, the traditional precursor to polyvinyl alcohol (PVA), is challenging due to the reactivity of the unconjugated α-acetoxy radical. We report the synthesis and characterization of PS-b-PVA block copolymers (BCPs) with tailorable PVA block lengths via RAFT polymerization of an alternative precursor, an aromatic organoborane comonomer BN 2-vinylnapthalene (BN2VN). RAFT homopolymerization of BN2VN (RB) using 2-cyano-2-propyl dodecyl trithiocarbonate (CPDT) is described. Solid-state NMR, ATR-IR, SEC and thermogravimetric analysis reveal significant differences between PS-b-PVA and RS-b-RB. The fate of the trithiocarbonate end-group during oxidative conversion of the C–B side chain to a C–OH side chain was studied; while a hydrated aldehyde (e.g., gem-diol) was hypothesized, conclusive evidence was not found.