Synthesis of Stimuli-Responsive, Deep Eutectic Solvent-Based Polymer Thermosets for Debondable Adhesives

Abstract

This paper demonstrates a macromolecular design for deep eutectic solvent (DES)-based polymer thermosets that are adhesive but removable on demand by depolymerization. For the design of a DES, a novel self-immolative polymerizable molecule capable of donating hydrogen bonds has been synthesized to form a room-temperature eutectic mixture when combined with another olefinic hydrogen bond acceptor. The physical properties of the liquid mixture have been characterized, and the mixture has been confirmed to be suitable for the formation of easily processable, resilient, transparent thermosets through click addition polymerization. The materials not only degrade on a molecular level as designed but also show interfacial adhesion onto various substrates, yielding a debondable polymer adhesive. The adhesive strength, which is comparable to that of commercial glue, decreases significantly in response to trace amounts of fluoride under benign conditions. As an example, after exposure to 0.01 M CsF, the bonded glass substrates easily separated within 16 h at room temperature. Similarly, the energy-efficient delamination of mixed composites was also achieved. We envisage that our design concept would benefit the development of functional polymeric materials that facilitate end-of-use processes.