Environmentally benign polyester design by room-temperature dehydration polycondensation

Abstract

Low-temperature polycondensation of methylsuccinic acid (MSA) (at 35°C), bromosuccinic acid (BSA), 2-bromoadipic acid (BAA) (at 40°C), and citraconic acid (CA) (at 60°C) with diols containing 1,3-propanediol (1,3-PD) and 1,4-butanediol (1,4-BD) were performed under reduced pressure (0.3 - 30 mmHg) using scandium trifluoromethanesulfonate [Sc(OTf)3], scandium trifluoromethanesulfonimide [Sc(NTf2)3], and polymer-supported scandium trifluoromethanesulfonate (PS-Sc) to give poly(alkylene succinate)s with Mn = 0.67 × 104-1.41 × 104 without transesterification (Mw/Mn = 1.4 - 2.1). The catalysts are recovered quantitatively and reused. Room-temperature polycondensation made it possible to use thermally unstable monomers containing carbon-carbon double bond and bromo functionalities, and α,ω-dihydroxyl polyesters as monomers. Also room-temperature polycondensation enabled us to combine polycondensation with atom-transfer radical polymerization (ATRP) via both "grafting from" and "grafting through" techniques, to hybridize with vinyl polymers. Furthermore, chemoselective dehydration polycondensation of dicarboxylic acids and diols having pendent hydroxyl group was attained.