Synthesis and thermal investigation of poly(propylene terephthalate-co-2,5-furan dicarboxylate) copolyesters

Herein, we report the synthesis of new poly(propylene terephthalate-co-2,5-furan dicarboxylate) (PPTF) copolyesters with high molecular weight. Copolymers having various PT/PF molar fractions were synthesized via a two-stage melt polycondensation reaction from the dimethyl esters of terephthalic acid (TPA) or 2,5-furandicarboxylic acid (FDCA) with 1,3-propanediol. The combination of the crystallization ability of PPT with the biobased nature of PPF could make the PPTF copolyesters very appealing. Based on nuclear magnetic resonance spectroscopy, the structure and the actual molar composition of the copolyesters were identified and all the copolymers were found to be random. The investigation of the cocrystallization behavior with XRD showed that isodimorphism predominates, and DSC confirmed the random nature of the copolymers by the presence of a minimum value of the melting temperature as a function of copolymers’ composition. Moreover, isothermal melt crystallization studies were conducted. The melting point depression was investigated through the implementation of a plethora of thermodynamic models, and it was found that the incorporation of the PF units into the PPT crystal was preferred. In all cases, the effect of the furan ring was noticeable, as the copolyesters with higher PT content demonstrated higher crystallization rates. Finally, through polarized light microscopy the spherulitic morphology of the polymers was examined.