Azobenzene-Containing Triblock Copolymer Adhesive Based on Light-Induced Solid-Liquid Phase Transition: Application to Bonding for Various Substrates

摘要

Azobenzene-containing block copolymers have been previously developed as light-induced reworkable adhesives that can undergo repeatable bonding/ debonding on demand, based on photoisomerization of the azobenzene moiety and concomitant softening/hardening of the azo polymer block. For practical use, the applicability of such adhesives to various types of substrates is important and is thus studied as one of their most fundamental properties in this work. Ultraviolet (UV)-transparent acrylic resin as well as non-transparent polycarbonate resin, polyethylene ones, and metallic aluminum substrates are utilized as substrates. UV-transparent acrylic resin is used as one of two substrates to investigate the photoisomerization process. The bonding/debonding process is successful for these substrates, and single lap shear tests show typical adhesion strengths of 1.5-2.0 MPa for the substrates investigated. UV irradiation induced a decrease in the adhesion strength to 0.03 MPa irrespective of the substrate type, indicating that the mechanism of the detachability is flow of the softened adhesive. Facile removal of the residual adhesive on the substrate is successfully demonstrated after detachment without any damage to the substrates by wiping the substrate with laboratory-grade disposable wipes wet with ethanol.