Harnessing Imine Chemistry for the Debonding-on-Demand of Polyurethane Adhesives

Traditional adhesives often result in irreversible bonds, hindering disassembly and recycling processes. In response to the growing demand for sustainable practices, researchers have explored alternative bonding solutions. Debonding-on-demand adhesives represent a breakthrough, enabling selective weakening or breaking of adhesive bonds when desired and facilitating efficient disassembly, repair, and recycling of bonded materials. This has profound implications across industries, including packaging, footwear, automotive, and electronics, where the recycling of bonded components plays a crucial role in resource conservation. Herein, we present the incorporation of an imine-based polyol derived from vanillin and polyetheramine into a model, one-component, polyether-based polyurethane adhesives. Such systems retained their thermal performance, exhibiting onset degradation temperatures of ∼320 °C and glass transition temperatures of ∼-50 °C, similar to the reference adhesive. Additionally, they demonstrated adhesive performance comparable to that of the reference system, with lap-shear strengths ranging from 1.7 to 2.1 MPa. In addition to that, imine polyol incorporated adhesives offered enhanced recyclability through on-demand debonding of the bonded substrates to obtain adhesive-free surfaces by acidic hydrolysis of the imine functional groups. These findings undoubtedly contribute to the advancement of sustainable material practices and promote a circular economy, emphasizing the importance of adhesive technology in addressing environmental challenges.