Synthesis and properties of biodegradable poly(ethylene succinate) containing two adjacent side methyl groups

To adjust the structure and properties of biodegradable poly(ethylene succinate) (PES), a series of novel poly (ethylene succinate-co-2,3-butylene succinate) (2,3-PEBS) copolyesters with low contents of 2,3-butylene succinate unit (2,3-BS) were successfully synthesized in this research via a two-stage melt polycondensation. 2,3PEBS showed the same main chain structure as PES, except that a few of two adjacent side methyl groups were randomly linked with the main chain; therefore, 2,3-PEBS may be regarded as novel PES containing two adjacent side methyl groups. The thermal parameters, crystallization behavior, and mechanical property of 2,3PEBS copolyesters and PES were systematically studied and compared with each other. The compositions of ethylene succinate (ES) to 2,3-BS deviated significantly from the feed ratio of ethylene glycol to 2,3-butanediol (2,3-BDO) due to the low reactivity of 2,3-BDO. The results revealed that the introduction of a small amount of two adjacent side methyl groups brought an obvious variation in the thermal and mechanical properties of PES. However, 2,3-PEBS displayed the same crystallization mechanism and crystal structure as PES. Through the introduction of a few of two adjacent side methyl groups, novel PES with significantly improved mechanical properties was synthesized, which should be interesting and important for a better understanding of the structure and properties to prepare novel biodegradable polymers from a sustainable viewpoint.