Reversible Photocuring of Liquid Hexa-Anthracene Compounds for Adhesive Applications

Reworkable adhesion of glass plates was demonstrated using colourless adhesives. This was achieved using anthracene-terminated liquid compounds with hexamer structures (2500g mol(-1)) as adhesives, which are photo-crosslinkable and thermo-degradable materials. It was found that the substitution position at the anthracene was important to obtain liquid-phase compounds at room temperature. However, although the compounds were liquid, they were too viscous to be used as adhesive. Therefore, they were mixed with 25wt.% of dibutyl phthalate to increase fluidity. The liquid mixture could then be applied to the glass substrates without further modification, and was curable via photodimerisation of anthracene moieties to tightly attach the glass substrates together. The cured material was stable up to 120 degrees C, but it returned to the original liquid state at room temperature after heating at 180 degrees C, resulting in the detachment of the substrates without applying any strong force. The cycles of the curing and liquefying processes was reproducible for at least five consecutive times.