A Model Decoupling Cohesive and Interfacial Properties of Adhesives: Boronic Ester-Functionalized Random Copolymers as a Case Study

This study presents a design strategy to decouple and tailor the cohesive and interfacial properties of adhesives within a single polymer system, enabling both high performance and on-demand recyclability. The strategy employs the precise synthesis of boronic ester-functionalized cycloolefin copolymers via ring-opening metathesis polymerization (ROMP), where interchain metathesis ensures a random monomer distribution irrespective of monomer reactivity difference. Cohesive and interfacial strength can be independently tuned by adjusting the copolymer composition and bonding conditions. Under optimized bonding conditions, the adhesive’s performance is governed by its intrinsic mechanical properties. This is evidenced by the parallel composition dependence observed between adhesive metrics (lap-shear strength, maximum extension, work of debonding) and mechanical parameters (fracture strength, elongation at break, toughness). A quantitative model is developed to decouple cohesive and interfacial strength and to predict overall adhesive performance. The cohesive strength, which parallels the trend of the polymer’s fracture strength, is governed by the copolymer composition. The interfacial strength depends on both composition and bonding conditions. By applying classical theories of polymer physics to the experimental data, a semiempirical equation is established to predict the interfacial strength as a function of these variables. The high interfacial strength is attributed to dynamic covalent bonds formed between boronic ester groups and hydroxyl groups on the substrate. Leveraging the dynamic B–O bonds at the interface, on-demand debonding through hydrolysis enables recovery and reuse of the polymer. This work provides a straightforward and controllable synthesis route for recyclable high-performance adhesives, and establishes a clear correlation linking monomer design to polymer structure, and ultimately to adhesive performance.