Enzymatic synthesis of biobased poly(1,4-butylene succinate-ran-2, 3-butylene succinate) copolyesters and characterization. Influence of 1,4-and 2,3-butanediol contents

Different (co)polyesters, poly(1,4-butylene succinate-ran-2,3-butylene succinate) (PBB'S), were enzymatically copolymerized at different 1,4-butanediol (1,4-BDO)/2,3-butanediol (2,3-BDO) molar ratios, with immobilized Candida antarctica lipase B (CALB). The synthesized macro molecular architectures were characterized by NMR, SEC, FTIR, WARS, MALDI-TOF MS, DSC, TGA and specific optical rotation. Based on an optimized process, PBB'S copolyesters were synthesized in high yield. A random distribution between both BDOs was obtained along the chain. (M) over bar (w) decreased with increasing 2,3-BDO content, from 26 to 6 kg/mol. The specific optical rotation decreased linearly with decreasing 2,3-BDO content, and can be used as a characterization technique to determine PBB'S composition. DSC results showed that an increase in 2,3-BDO content raised the Tg and reduced the degree of crystallinity, leading to amorphous materials for 2,3-BDO content higher than 47 mol.%. Synthesized copolyesters exhibited a good thermal stability, higher than 250 degrees C, with a degradation profile depending on the 1,4-BDO/2,3-BDO ratio.