Molecular design of azobenzene-containing photoresponsive phase change materials with energy storage and photolithography potentials

Photoresponsive phase change materials (PPCMs) based on azobenzene are attractive in various fields. However, small azobenzene molecules-based materials rarely gain photoinduced solid-liquid phase change at room temperature, due to the formed high molecular packing density with the absence of sufficient free volume for isomerization. In this study, aiming at developing a new type of PPCMs, two azobenzene-containing ammonium surfactants with bulky head groups are designed and synthesized. The designed bulky head groups could efficiently reduce the molecular packing density, facilitating the solid-liquid phase change of such PPCMs under UV light. Via the fabrication of ammonium surfactants with double aliphatic chains for further reducing the molecular packing density, the reported PPCMs gain more complete and faster phase change, which could be used as potential energy storage and photolithography materials. This study provides a new molecular designing strategy for fabricating azobenzene-based PPCMs. Two azobenzene-containing ammonium surfactants with bulky head groups are designed and synthesized as photoresponsive phase change materials, showing good potentials for energy storage and photolithography. [Display omitted] •A designing strategy for gaining photoinduced phase change materials is developed.•Small azobenzene compounds achieve photoinduced solid-liquid phase change.•Bulky head groups reduce the molecular packing density of azobenzene surfactants.•Fabrication of non-azobenzene surfactant leads to complete and faster phase change.•The reported azobenzene surfactants could be potential energy storage materials.