Synthesis of thermoplastic elastomers with high biodegradability in seawater

As a promising biodegradable and biorenewable alternative to ubiquitous petrochemical plastics, poly(L-lactide) (PLLA) can be widely employed in biomedical and pharmaceutical fields. In this work, triblock copolymers, poly(L-lactide)-b-poly(2-methyl-1,3-propanediyl adipate)-b-poly(L-lactide) (PLLA-b-PMPA-b-PLLA)s, were synthesized by two-step polymerization from 2-methyl-1,3-propanediol (MP), adipic acid (AA) and L-lactide (LLA) as new biodegradable thermoplastic elastomers. The copolymers exhibited glass-transition temperature at below −40 °C and melting temperature at 140–160 °C. These copolymers showed much higher elongation at break and lower tensile modulus than those of PLLA. Enzymatic degradation tests of the obtained copolymers were performed using proteinase K and lipase PS as catalysts in hydrolysis reaction to demonstrate rapid degradation for these copolymers. Seawater biodegradability test was conducted for 28 days for each sample. The triblock copolymer and PMPA homopolymer were found to show about 50% biodegradation within 28 days representing very high biodegradable property in seawater.