Design of a High-Performance Dismantlable Adhesion System Using Pressure-Sensitive Adhesive Copolymers of 2-Hydroxyethyl Acrylate Protected with -Butoxycarbonyl Group in the Presence of Cross-Linker and Lewis Acid.

A dismantlable adhesion system satisfies both a strong bonding strength during use and a quick debonding process on demand in response to an external stimulus as a trigger for dismantling. In this study, we synthesized acrylate copolymers consisting of 2-(-butoxycarbonyloxy)ethyl acrylate (BHEA), 2-ethylhexyl acrylate (2EHA), and 2-hydroxyethyl acrylate (HEA) as the repeating units and evaluated the properties as dismantlable adhesives. First, the thermal degradation behavior of the obtained polymers was investigated by thermogravimetric analysis and IR spectroscopy. The BHEA-containing polymers were thermally stable during heating at a temperature below 150 °C, but they rapidly degraded, i.e., the deprotection of the -butoxycarbonyl groups occurred during heating at 200 °C. The onset temperatures for the deprotection depended on the BHEA and HEA contents and their sequence structures because the hydroxy group in the side chain accelerated the deprotection via an autocatalytic reaction mechanism. Shear holding power and 180° peel tests were carried out with the pressure-sensitive adhesive tapes using the BHEA-containing copolymers as the adhesive materials. The copolymers consisting of the BHEA, 2EHA, and HEA units with 25.7, 35.0, and 39.3 mol %, respectively, exhibited the highest adhesion strength and the subsequent quick reduction of the adhesion strength by heating during the dismantling process. The addition of hexamethylene diisocyanate as the cross-linker and Zn(acac) as the Lewis acid to the adhesive polymers was demonstrated to be valid for the design of high-performance dismantlable adhesion systems. A change in the rheological properties during the dismantling process was important for a quick response and selective interfacial failure between the substrate and the adhesive.