Strong, Resilient, and Sustainable Aliphatic Polyester Thermoplastic Elastomers

Thermoplastic elastomers (TPEs) composed of ABA block polymers exhibit a wide variety of properties and are easily processable as they contain physical, rather than chemical, cross-links. Poly(γ-methyl-ε-caprolactone) (PγMCL) is an amorphous polymer with a low entanglement molar mass (Me = 2.9 kg mol–1), making it a suitable choice for tough elastomers. Incorporating PγMCL as the midblock with polylactide (PLA) end blocks (fLA = 0.17) results in TPEs with high stresses and elongations at break (σB = 24 ± 2 MPa and εB = 1029 ± 20%, respectively) and low levels of hysteresis. The use of isotactic PLA as the end blocks (fLLA = 0.17) increases the strength and toughness of the material (σB = 30 ± 4 MPa, εB = 988 ± 30%) due to its semicrystalline nature. This study aims to demonstrate how the outstanding properties in these sustainable materials are a result of the entanglements, glass transition temperature, segment–segment interaction parameter, and crystallinity, resulting in comparable properties to the commercially relevant styrene-based TPEs.