Influence of ether bond on degradation property of PBS-based copolymers at molecular level using molecular simulations

In order to understand the relationship between enzymatic degradation and the structure of PBS-based copolyesters PBS-co-DEGS and PBS-co-BDGA modified with monomers (diethylene glycol and diglycolic acid) were synthesized and the enzymatic degradation property was studied. Pseudomonas cepacia lipase was selected as the catalyst, while the chloroform was used as solvent. The results indicated that both PBS-co-DEGS and PBS-co-BDGA can be catalytically degraded by PC lipase but they were different. The hydrolysis of PBS-co-BDGA improved greatly and the degree of hydrolysis of PBS-co-BDGA was almost consistent with the degree of degradation due to the introduction of DGA. Similarly, thermal property changes were also observed with a decrease of the decomposition temperature of 5 and 50% sample in most cases. The enzymatic degradation of PBS-based copolymers produced not only linear segments, but also cyclic oligomers. Furthermore, PBS-co-BDGA generated more oligomers than PBS-co-DEGS. According to the results of molecular docking, the free energy of binding between PCL and the substrate in chloroform was in the order BDGAB > DEGSDEG > BSB. That is, the docking of the substrate containing BDGA in the active site of PCL was more stable than any other ones.