Rapid synthesis of sustainable poly(ethylene 2,5-furandicarboxylate)-block-poly(tetramethylene oxide) multiblock copolymers with tailor-made properties via a cascade polymerization route

Abstract

Bio-based 2,5-furandicarboxylic acid (FDCA) is a promising monomer for the substitution of fossil-based terephthalic acid, yet its condensation polymerization with corresponding diols to high quality polyesters remains challenging due to the degradation and discolouration from side reactions. We report here a cascade polycondensation-coupling ring-opening polymerization (PROP) strategy towards the rapid synthesis of poly(ethylene 2,5-furandicarboxylate)-block-poly(tetramethylene oxide) multiblock copolymers (mBCPs), (PEF-b-PTMO-b-PEF)n, via the vacuum melt polymerization of cyclic oligo(ethylene 2,5-furandicarboxylate)s (COEFs) with PTMO diols. Due to the rapid cascade polymerization, the side reactions were suppressed and poly(ether ester) mBCPs with high number-average molecular weights (Mn > 30 kg/mol) were obtained within 60 min. The segmental length, block number and soft/hard weight ratio can be well-controlled by the polymerization conditions, and their structure-property relationship was investigated. In these double-crystalline mBCPs, the melting temperature and degree of crystallinity of PEF segments increase with PEF content, while those for PTMO are less affected. These mBCPs form bicontinuous disordered phase separation morphologies, with the domain size decreases with the increment of PTMO content, the total block copolymer molecular weight, and the reduced segmental length. With the crystalline PEF domains forming the physically-crosslinking points, these mBCPs show typical thermoplastic elastomer properties with elongations exceeding 400%. The strength and Young's modulus increase with PEF content, while the elongation at break decreases. Increment of block number enhances both the strength and elongation at break for mBCPs. In addition, these sustainable mBCPs show biodegradable properties controlled by the hard/soft weight ratio and crystallinity of PEF blocks. Our cascade polymerization method provides an efficient method for the rapid preparation of sustainable high value-added thermoplastic elastomers with tailor-made properties.