Bio-based ABA triblock copolymers with central degradable moieties

Abstract

A set of (poly-α-methylene-γ-butyrolactone)–co-(poly-δ-decalactone)–co-(poly-α-methylene-γ-butyrolactone) (PMBL-co-PDL-co-PMBL) ABA block copolymers containing different stimuli cleavable groups at the central point of the poly(δ-decalactone) (PDL) block were synthesized by a combination of Ring Opening Transesterification Polymerization (ROTEP) of DL, diol end-group functionalization as α-bromoester and Atom Transfer Radical Polymerization (ATRP) of α -methylene-γ-butyrolactone (MBL). Diols containing acetal, spiroacetal, thioacetal and disulphide units were used as initiators for the bulk room temperature controlled polymerization of δ-decalactone (DL) using 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as catalyst. PDL diols were functionalized in a one-pot two-steps procedure using N-(2-bromoisobutyryl)imidazole (BiB-Im). The resulting macroinitiators were chain extended by atom transfer radical polymerization (ATRP) in DMF at 50 °C using MBL as methacrylic-like monomer and the conventional CuCl/CuCl2/2,2′-bipyridine catalyst system. The cleavage behaviour of the copolymers under reductive, acidic and photooxidative conditions has been studied and the resulting AB block copolymers structurally characterized.