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

Abstract

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. 2,3-PEBS 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 2,3-PEBS 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.