Structural adhesives are mostly made of thermoset polymeric materials with irreversible chemical bonding that exhibits strong but brittle behavior. Those thermoset adhesive materials are mostly single-used and ultimately end up in a landfill without an option for recycling. Therefore, it is highly desirable to develop recyclable/reusable tough adhesive materials that can provide high strength, high load-bearing capability, and longevity of bonded materials. Such tough adhesives can minimize adhesive failure, provide a path for recycling, and prevent unnecessary replacements of bonded materials, thus ultimately save significant energy and costs. Here, we report a design of tough reversible adhesive materials enabled by incorporating dynamic covalent bonds of boronic ester into commodity triblock thermoplastic elastomers, that reversibly bond with various fillers and substrates. A commodity thermoplastic elastomer, polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (SEBS) was modified with boronic ester and reinforced using unmodified silica nanoparticles (SiNPs). The dynamic covalent crosslinking between hydroxyl groups on SiNPs, boronic ester group on SEBS enables reprocessability, mechanical robustness, and rebondable tough adhesive property on various hydroxy-terminated surfaces such as aluminum, steel, and glass, which are also validated by density functional theory calculations. 20 wt % SiNPs loaded composite exhibit very strong adhesion at 9.38 ± 1.39 MPa and work of debonding of 733.96 ± 71.58 Nm^-1 on aluminum substrate, which exceeds many existing commercial adhesives. This talk will demonstrate a simple and efficient way to make a tougher adhesive with significantly high strength, ductility, and reprocessability, that will open new opportunities in many applications.

Christopher Bowland

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