A Chemically Recyclable Thermoplastic Elastomer Synthesized with Redox Switchable Polymerization

Poly(lactic acid) (PLA) as a biodegradable and bio-derived polyester has limited application due to its brittleness. In an effort to increase the flexibility, a redox-switchable catalytic system was developed to make A-B-A’ triblock copolymers containing stiff PLA end blocks and a flexible poly(tetrahydrofuran-<i>co</i>-epoxide) midblock. The tensile test demonstrated high flexibility of the triblock (strain at break ε_b up to 200%) compared with PLLA (ε_b &lt; 10%). The mechanical properties were dependent on the amount of tetrahydrofuran (THF) repeating units in the mid-block: low THF incorporation led to more thermoplastic features while higher THF incorporation resulted in more rubbery materials. In addition to being derived from commodity monomers like lactide and THF, the triblock copolymer can be depolymerized to their constituent monomers. A reactive distillation system with a dual catalyst system was designed that allowed us to recover THF and lactide monomers from the thermoplastic elastomer.