Synthesis of poly(butylene terephthalate)-block-poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) multiblock terpolymers via a facile PROP method

Abstract

We present here the application of in situ cascade polycondensation-coupling ring-opening polymerization (PROP) method for the facile synthesis of a series of three-component poly(butylene terephthalate)-block-poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) multiblock terpolymers (PBT-b-PEO-b-PPO-b-PEO-b-PBT)n, using cyclic oligo(butylene terephthalate)s (COBTs) as monomers and dihydroxyl end-functional PEO-b-PPO-b-PEO (EPE) as macroinitiator. The structure details of these copolymers were characterized by 1H-1H gCOSY and 1H-13C gHSQC NMR spectra. With the assignment of multiblock chain ends, block segmental ends and corresponding groups for each segment, the number-average molecular weights for multiblock terpolymers and each block segment were estimated by the quantitative 1H NMR spectra. Polymerization kinetics studies confirm the PROP mechanism. With crystalline PBT and PEO segments, the multiblock terpolymers are double-crystalline polymers, where the melting point and crystallinity of PBT and PEO segments increase with corresponding PBT and PEO content, respectively. The covalent linking of PBT segments with PEO segments leads to the confined crystallization environment for both blocks, where a strong depression on melting point of PEO crystals was observed, which becomes amorphous at an EPE triblock content of 50%. TEM and SAXS results show interesting lamella-like microphase separation morphologies in these multiblock terpolymers.