Synthesis, Properties, and Biodegradability of Thermoplastic Elastomers Made from 2-Methyl-1,3-propanediol, Glutaric Acid and Lactide.

Lamya Zahir,Norioki Kawasaki,Ryo Tanaka,Yuushou Nakayama,Atsuyoshi Nakayama,Takumitsu Kida,Takeshi Shiono,Naoko Yamano

doi:10.3390/life11010043

Abstract

An innovative type of biodegradable thermoplastic elastomers with improved mechanical properties from very common and potentially renewable sources, poly(L-lactide)-b-poly(2-methyl-1,3-propylene glutarate)-b-poly(L-lactide) (PLA-b-PMPG-b-PLA)s, has been developed for the first time. PLA-b-PMPG-b-PLAs were synthesized by polycondensation of 2-methyl-1,3-propanediol and glutaric acid and successive ring-opening polymerization of L-lactide, where PMPG is an amorphous central block with low glass transition temperature and PLA is hard semicrystalline terminal blocks. The copolymers showed glass transition temperature at lower than −40 °C and melting temperature at 130–152 °C. The tensile tests of these copolymers were also performed to evaluate their mechanical properties. The degradation of the copolymers and PMPG by enzymes proteinase K and lipase PS were investigated. Microbial biodegradation in seawater was also performed at 27 °C. The triblock copolymers and PMPG homopolymer were found to show 9–15% biodegradation within 28 days, representing their relatively high biodegradability in seawater. The macromolecular structure of the triblock copolymers of PLA and PMPG can be controlled to tune their mechanical and biodegradation properties, demonstrating their potential use in various applications.

Highlights

Nowadays, biodegradable polymers have been increasingly attracting attention to substitute non-biodegradable products as sustainable alternatives to protect the environment from plastic pollution [1]
ABA type triblock copolymers consisting of two immiscible blocks, a soft central block (B) and two hard terminal blocks (A), behave as thermoplastic elastomers (TPEs), which can be varied between hard plastics and soft rubbers depending on the compositions and microarchitectures [2,3]
Dihydroxyl terminated PMPG were synthesized by a two-stage process of the bulk polycondensation from MP and glutaric acid (GA)

Summary

Introduction

Biodegradable polymers have been increasingly attracting attention to substitute non-biodegradable products as sustainable alternatives to protect the environment from plastic pollution [1]. Aliphatic polyesters, such as poly(L-lactic acid) (PLA), poly(ε-caprolactone) (PCL), poly(butylene succinate) (PBSu), poly(3-hydroxybutyrate). PLA is one of the most promising biodegradable polymers due to its biocompatibility and availability from renewable biomass, its hard and brittle nature limits its application. PLA can be applied as hard terminal blocks of TPE by the introduction of a soft central block [4]

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