Light Stimuli-Responsive Degradable and Tough Polymeric Materials with Movable Cross-Links

Both strong and easily dismantlable adhesive systems are required to realize a sustainable society by recovering and reusing substrates. Introducing topological cross-links with cyclodextrins (CDs) into adhesives can improve their adhesive strength. In this study, we prepared movable cross-linked poly(ethyl acrylate) (PEA-TAcγCD) with polymerizable CDs and acid-degradable bonds (TAcγCDAAmMe) for both strong and dismantlable adhesion. The O-amidomethyl bond, which links CD to a polymerizable functional group, can be degraded by mixing Brønsted acid. By combining PEA-TAcγCD with photoacid generators, we successfully controlled the mechanical properties by cleaving the movable cross-links upon light stimulation. The degradation mechanism of TAcγCDAAmMe by photoacid generators was confirmed by mass spectrometry. In addition, the cleavage of movable cross-linking points via light stimulation was demonstrated by both the alteration of mechanical properties and chain relaxation of the system, which were evaluated by utilizing tensile tests and dynamic mechanical analysis, respectively. Therefore, the light-responsive degradable elastomer appeared applicable as an easily dismantled on-demand adhesion system. Using light stimulation, the adhesion strengths with the same or dissimilar substrates were reduced. The easy dismantling of the adhesion system by applying the acid degradability of TAcγCDAAmMe enabled excellent adhesive properties derived from the movable cross-links and easy dismantling by light stimulation. Facilitating the disassembly, collection, and reuse of resources will contribute to the realization of a sustainable society.