Ring-Opening Copolymerizations of a CO2-derived δ-Valerolactone with ε-Caprolactone and L-Lactide

Ring-opening random, gradient, and block copolymerizations of the CO2¬-derived δ-valerolactone 3-ethyl-6-vinyltetrahydro-2H-pyran-2-one (EtVP) with ε-caprolactone (ε-CL) and L-lactide (LLA) are reported. By employing both concurrent and sequential addition strategies, a variety of thermal and physical properties could be accessed. Concurrent copolymerization of EtVP with ε-CL yielded gradient copolymers with low glass transition temperatures, while block copolymerizations via sequential addition led to semi-crystalline materials regardless of monomer feed ratios. For LLA copolymerizations, glass transition temperatures increased with LLA incorporation regardless of addi-tion method, but higher Tg values were observed in block copolymerizations from sequential addition. Tensile testing of a poly(EtVP-b-LLA) with molar ratio of 40:60 EtVP:LLA resulted in σ = 0.8 MPa, E = 5.6 MPa and 83% elongation at break. The chemical recyclability of EtVP-based copolymers was explored as an end-of-life option. Both ε-CL and LLA copolymers could be recycled, with block copolymers giving higher yields of recycled monomers than random copolymers.