Coordinative Ring-Opening Copolymerization of Limonene Carbamate and ε-Caprolactone Toward Phosgene- and Isocyanate-Free Polyesterurethane Block-Copolymers with Tunable Properties

Polyesterurethanes are versatile polymers widely utilized in applications such as foams and adhesives, yet their industrial production relies on toxic and carcinogenic diisocyanates. To address this, isocyanate- and phosgene-free synthetic methods have been explored, with ring-opening polymerization of cyclic carbamates emerging as a promising alternative. This study presents the coordinative ring-opening copolymerization of limonene-based cyclic carbamates with ε-caprolactone to synthesize AB-block polyesterurethanes. Using the presented method, tunable block copolymer compositions were achieved, verified by NMR, GPC, and FT-IR analyses. Thermal and optical characterizations by DSC and UV–vis revealed an adjustable glass transition temperature between −9°C and −59°C and transmittance up to 84% for PLU-b-PCL (49:51), while tensile testing demonstrated customizable mechanical properties. Notably, PLU-b-PCL (5:95) exhibited an elongation at break of 582%. These findings provide a basis for sustainable polyesterurethane synthesis by ring-opening copolymerization and demonstrate the versatility of this method.