Novel eco-friendly random copolyesters of poly(butylene succinate) containing ether-linkages

Poly(butylene succinate/diglycolate) random copolymers (P(BSxBDGy)) of various compositions were synthesized and characterized from the molecular, thermal, structural and mechanical point of view. All the polymers showed a good thermal stability and at room temperature they appeared as semicrystalline materials. The main effect of copolymerization was a lowering in the crystallinity and a decrease of Tm respect to homopolymers. The dependence of Tm on composition for copolymers with high butylene succinate unit content was well described by Baur’s equation. WAXD measurements indicated that two different crystalline phases are present, depending on composition: copolymers with high BS unit content are characterized by PBS crystal phase, whereas those rich in BDG co-units crystallized in PBDG lattice. Amorphous samples showed a monotonic increment of Tg as the content of BDG units is increased and this can be explained on the basis of interchain interactions, due to the high electronegativity of ether–oxygen atoms. A Fox-type equation was found to fit the Tg data of completely amorphous samples, permitting the extrapolation of pure PBS Tg value for the completely amorphous polymer.