Coordination ring-opening transamidation copolymerization of cyclic lactones and lactams towards circular and biodegradable poly(ester amide) adhesives

Abstract The efficient synthesis of poly(ester amide)s (PEAs), which combine polyamide-like mechanical strength with polyester-like biodegradability, has remained a longstanding challenge. Herein, we introduce a unique coordination ring-opening transamidation copolymerization (CROTCP) mediated by a tetranuclear titanium catalyst. This reaction allows for the copolymerization of ε-caprolactone and ε-caprolactam under mild conditions, thereby overcoming the high-temperature and side-reaction issues associated with conventional lactam polymerization. Furthermore, it offers a route to directly upcycle polyesters into poly(ester amide)s through CROTCP. The resulting PEAs exhibit tunable compositions, high molecular weights, exhibiting tensile strengths up to approximately 55.5 MPa and elongation at break exceeding 1300 %. As adhesives, they achieve >15 MPa lap shear strength on stainless steel, outperforming commercial benchmarks. These PEAs enable closed-loop chemical recycling and show rapid degradability under composting conditions, offering a sustainable platform for high-performance biodegradable adhesives.