The direct and reversible transformation of matter between the solid and liquid phases by light at constant temperature is of great interest because of its potential applications in various manufacturing settings. We report a simple molecular design strategy for the phase transitions: azobenzenes having para-dialkoxy groups with a methyl group at the meta-position. The photolithography processes were demonstrated using the azobenzene as a photoresist in a single process combining development and etching of a copper substrate.

The direct and reversible solid-liquid phase transitions by photochromic reactions at constant temperature are of interest because of potential applications in reusable adhesives, photoresists and so on. We report photoinduced solid-liquid phase transitions in rod-shaped azobenzenes, possessing a methyl group at the 3-position and alkoxy groups with different chain length (Cn = 1-18) at the 4-and 4'-positions. Thermal property, photochemical property, and adhesive properties were investigated. We found that the azobenzenes with alkyl chain length of 6-10 showed relatively fast photoinduced solid-liquid phase transition than that with shorter (Cn = 1-5) and longer (Cn = 11-18) ones. Tensile shear strength were measured by using these azobenzenes as photoresponsive adhesives. Irradiation with UV light (365 nm) induced the phase transition to the liquid phase and the adhesion strength values decreased to almost zero. Then the irradiation with visible light (450 nm) recovered the adhesion strength.

Crystals of 4-methoxyazobenzene move on water surface and the motion is triggered by irradiation with ultraviolet light. The propulsion is produced by dissolution of the photo-generated cis isomer, which is produced by the photoinduced crystal-liquid phase transition. A photoresponsive boat was also prepared by a filter paper adsorbed with azobenzene.

Control over the initiation of enzymatic degradation of biodegradable polymers was demonstrated by tuning the solid-molten state of a surface coated azo-compound with light irradiation.

The synergy of continuous processing and microwave heating technologies has unlocked scalable (g/h), safe and efficient reaction conditions for synthesis of fullerene/indene-based organic photovoltaic acceptor materials in a nonchlorinated solvent with levels of productivity unparalleled by previous syntheses. The microwave flow reactor sustains high temperature while employing short residence times, reaction conditions which uniquely allow the selective synthesis of fullerene/indene monoadducts. Design of experiments analysis revealed residence time as the most crucial factor for conversion and selectivity control.