Controlling a polymer adhesive using light and a molecular switch.

A thermally remendable polymer was synthesized by the Diels-Alder reaction between dithienylfuran and maleimide monomers to generate a photoresponsive diarylethene. UV light (312 nm) and visible light (>435 nm) "gate" the reversibility of the Diels-Alder reaction and turn the self-healing properties of the polymer "off" and "on", respectively. After exposure to UV light, the strength of the polymer as an adhesive is enhanced. Visible light weakens the adhesive.