Diels-Alder polyurethanes for reversible-by-design adhesives and coatings

Abstract

Adhesively bonded joints with debonding-on-demand characteristics are required to combine high mechanical response with improved durability and sustainable end-of-life management. In this work, a novel polyurethane system based on Diels-Alder (DA) chemistry is proposed as a reusable-by-design solution for high-strength adhesives and healable coating applications. The material was synthesized through a solvent-free and catalyst-free two-step procedure, without the need of purification steps, enabling straightforward manufacturing. The resulting dynamic DA network exhibits an optimal balance between mechanical performance and thermal reversibility, enabling controlled debonding, reuse and healing. The system demonstrates strong adhesion on a wide range of substrates, including steel, wood, glass, and fiber-reinforced composites, achieving single-lap-joint shear strengths up to 11 MPa, pull-off strength values exceeding 11 MPa, together with adequate hardness and chemical resistance. The reversible nature of the network enables debonding and rebonding cycles with suitable retention of mechanical properties. Overall, the proposed DA-based polyurethane represents a versatile candidate for reversible adhesives and coatings, offering a compelling combination of mechanical performance and functionality through a simple manufacturing process.