A Cascade Polymerization Method for the Property Modification of Poly(butylene terephthalate) by the Incorporation of Isosorbide

Poly(butylene terephthalate) (PBT) is an important engineering plastic with good mechanical properties. We report herein the incorporation of biobased isosorbide into PBT by a green in situ cascade polycondensation-coupling ring-opening polymerization (PROP) method via the melt polymerization of commercially available isosorbide as initiator and cyclic oligo(butylene terephthalate)s (COBTs) as monomer. By varying the feeding weight ratio of isosorbide to COBTs, poly(butylene-co-isosorbide terephthalate) (PBIT) copolyesters with different content of isosorbide (5–20%) were synthesized. The structure of the PBIT copolyesters was characterized by 1H quantitative and 2D 1H–1H gCOSY NMR spectra. Kinetics studies confirm the PROP mechanism, which shows the advantage of high atom economy (89–99%). Property investigation of the sustainable PBIT copolymers shows that their thermal decomposition temperature increased slightly compared to PBT homopolymers, and the glass transition temperature increases with isosorbide content, while the melting and crystallization temperatures, crystallinity, and storage modulus decrease accordingly. Our PROP method provides a facile method for the synthesis of biodegradable and sustainable PBIT copolymers, with improved properties that could extend their applications in engineering plastics.