Photoinduced Regulation of the Heat Resistance in Polymer Networks with Diarylethene-Conjugated Reversible Covalent Cross-Links.

A cross-linker with a diarylethene-conjugated Diels-Alder adduct (DAE/DA) was synthesized and applied in a radical polymerization system to afford polymer networks whose dynamic nature can be changed reversibly by photoirradiation. Free-radical polymerization of hexyl methacrylate and the DAE/DA-based cross-linker furnished an insoluble and transparent poly(hexyl methacrylate) network with DAE/DA moieties at their cross-linking points, which undergo de-cross-linking via a thermally induced retro-DA reaction upon heating. The photoregulation of such a thermal de-cross-linking reaction in DAE/DA-based polymer networks was demonstrated by swelling experiments and tensile tests, revealing drastic changes in the heat resistance and mechanical properties upon exposure to UV-vis irradiation.