Competition and miscibility of isodimorphism and their effects on band spherulites and mechanical properties of poly(butylene succinate-co-cis-butene succinate) unsaturated aliphatic copolyesters

Unsaturated copolyesters poly(butylene succinate-co-cis-butene succinate) (P(BS-co-cBS)) were the first time prepared by polycondensation in combination with stannous octoate as catalyst and 4-methoxyphenol as radical inhibitor, achieving linear random copolyesters with a number-average molecular weight up to 38.2 kg/mol. The cis-2-butene-1, 4-diol used in this work showed a peculiarity of no isomerization or cross-linking side reaction even at high reaction temperatures, due to the high chemical stability of the unconjugated cis-double bond. Isodimorphic behavior between butylene succinate (BS) and cis-butane succinate (cBS) in P(BS-co-cBS) was evidenced by DSC and WARD analyses. Then, the competition and miscibility of isodimorphism between BS and cBS units were further investigated by thermodynamic analyses. The significant discrepancy in competition and miscibility between BS and cBS units from conformational geometry demonstrated unique physicochemical properties and structure-properties relationships in such system of unsaturated copolyesters. A great impact of competition and miscibility on band spherulites and mechanical properties of the copolyesters was observed and discussed. In conclusion, our work here not only clarifies the effect of cis-double bond on isodimorphism in the unsaturated copolyesters, but also gives an insight into the mechanism of how the competition and miscibility regulates their physical properties. (C) 2018 Elsevier Ltd. All rights reserved.