Novel Biobased Double Crystalline Poly(butylene succinate)-b-poly(butylene 2,5-thiophenedicarboxylate) Multiblock Copolymers with Excellent Thermal and Mechanical Properties and Enhanced Crystallization Behavior

Novel biobased double crystalline poly(butylene succinate)-b-poly(butylene 2,5-thiophenedicarboxylate) (PBS-b-PBTh) multiblock copolyesters with excellent thermal and mechanical properties were prepared from two hydroxyl-terminated PBS-diol and PBTh-diol prepolymers via a chain extension reaction. Both PBS and PBTh segments were semicrystalline, with the aliphatic PBS segment being the soft segment while the aromatic PBTh segment was the hard segment. In the case of PBS-b-PBTh, the two segments were partially miscible in the amorphous region; moreover, the melting temperature of each segment still remained very high compared with that of each homopolyester PBS and PBTh. The melt crystallization behavior of both segments was enhanced in the case of PBS-b-PBTh, which was attributed to different mechanisms. The crystal structure study revealed that both segments crystallized separately and showed the characteristic diffraction peaks, respectively. Compared with that of PBS, PBS-b-PBTh displayed a significant increase in the elongation at break while still maintaining a relatively high break strength. This research provides some new insights to synthesize biobased polyesters with excellent thermal and mechanical properties, which should be interesting from a sustainable viewpoint.