Homo- and Hetero-Recyclable Polyesters with High Refractive Index from CO2, 1,3-Butadiene and Thiols

α-Ethylidene-δ-vinyl-δ-valerolactone (EVL) is the only intermediate to synthesize copolymers of CO2 with 1,3-butadiene whose ring-opening polymerization (ROP), however, is obstructed by the tiglate group. The saturation of the conjugated double bond is essential to the living ROP of EVL, while previous reports involve irreversible hydrogenation. In the contribution, EVL derivatives are synthesized through Michael addition reaction to saturate the conjugated double bond as well as introduce various groups to synthesize polyesters with tunable glass-transition temperatures (Tg) from -45 °C to 3 °C and excellent refractive index between 1.64 and 1.85. Living and controlled polymerizations lead to polyesters with designable number average molecular weights (Mn = 6.9-12.8 kg∙mol-1) and narrow dispersities (Đ = 1.08-1.19). The obtained polyesters are able to be recycled to the corresponding monomers which can prepare comparable polymers with identical side groups, realizing the homo-recycling. The monomers are capable of being recycled to EVL and thiols through retro-Michael addition reaction, and then the recycled EVL can be re-functionalized to generate a new monomer which produces a polyester with another side group, fulfilling the hetero-recycling. We propose an “addition-elimination-re-addition” strategy for EVL derivatives and the corresponding polyesters.