# Sustainable Thermoplastic Elastomers from Commercial Cyclic Esters: One-Pot Synthesis of Poly(l‑lactide)‑b‑(δ-hexalactone-stat-ε-caprolactone)‑b‑(l‑lactide) and Its Chemical Recycling to the Monomers

## TL;DR

Scientists created a new type of recyclable thermoplastic elastomer using a one-pot synthesis method and achieved high monomer recovery through chemical recycling.

## Contribution

A one-pot synthesis method for ABA triblock copolymers with precise control and full chemical recyclability under mild conditions.

## Key findings

- ABA triblock copolymers were synthesized using an Fe(II)-based catalyst in a single reactor.
- The material properties ranged from soft elastomers to toughened PLA depending on block composition.
- Chemical recycling recovered >90% of the original monomers under mild thermal conditions.

## Abstract

We report the one-pot 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-T
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)-b-(δ-hexalactone-stat-ε-caprolactone)-b-(l-lactide) triblock copolymers. The one-pot 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.