Toughness Improvement of Carbene Bioadhesives via In Situ Polyester Extension

ABSTRACT Carbene‐based adhesives suffer from weak cohesive strength due to molar mass limits to ensure transparency. A feasible approach to improve cohesion relies on polymer chain extension utilizing light‐activated ring‐opening polymerization of lactones. Key material properties such as yield strength, elongation, and toughness evaluate if the structure‐property relationships support chain extension as a viable strategy within a bioadhesive design intent. Rapid polymerization and gelation (< 1 h) occurred under ambient temperatures with δ‐valerolactone and ε‐caprolactone monomers, carbene‐based adhesive CaproGlu as the ROP initiator, and selected organocatalysts. A dilution of up to 40 mol% δ‐valerolactone monomer shows non‐inferior yield strength and toughness as neat CaproGlu for both lap shear and peel tests, implying that ROP enhances the cohesive strength of the formulation. One‐component (1C) formulations found irradiated iodonium salts catalyze in situ formation of polyesters from δ‐valerolactone, with a timed delay before gelation.