Sustainable Thermoplastic Elastomers from Commercial Cyclic Esters: One-Pot Synthesis of Poly( <scp>l</scp> -lactide)- <i>b</i> -(δ-hexalactone- <i>stat</i> -ε-caprolactone)- <i>b</i> -( <scp>l</scp> -lactide) and Its Chemical Recycling to the Monome

We report the <i>one-pot</i> synthesis of ABA triblock copolymers composed of poly-(l-lactide) (PLA) as hard segments and δ-hexalactone/ε-caprolactone (HL/CL) copolymers as soft midblock. Use of an environmentally benign and highly active and living Fe-(II)-based catalyst enabled precise molecular design and control over copolymer architecture, providing low-<i>T</i> _g, amorphous statistical HL/CL dihydroxy-terminated copolymers, which could be chain extended with l-lactide in the same reactor, resulting in poly-(l-lactide)-<i>b</i>-(δ-hexalactone-<i>stat</i>-ε-caprolactone)-<i>b</i>-(l-lactide) triblock copolymers. The <i>one-pot</i> synthetic route enabled control of block composition and length, resulting in material property profiles ranging from silicone-like soft elastomers to SBS-like rubbers, and to toughened PLA. Finally, efficient chemical recycling to the pristine monomers with >90% recovery was achieved by catalytic thermal depolymerization under mild conditions.