fig4

Figure 4. Experimental demonstration of selective crystallization of liquid sample and the heat release monitoring via photoinduction. (A) Schematic illustration of the selective crystallization of liquid sample via photoinduction. Selective photoinduced crystallization process of (B) Azo-Cl as a representative example of halogen-grafted Azos and (C) Azo-OEt as a representative example of alkoxy-grafted Azos, which were irradiated with visible light (420 nm) at ambient temperatures of 35 and -20 °C, respectively. The left side of the liquid film is covered with cardboard to preserve the cis-isomers in the stable liquid state. Optical microscope images of the left side, right side, and center of the film, indicating cis-isomers at the liquid phase, solid phase, and the liquid and crystalline solid boundary, respectively. The images on the top corners of (B) and (C) depict the cis-liquid samples (left) before and (right) after the 420-nm light irradiation. Normalized UV-Vis spectra of the uncovered parts for (D) Azo-Cl and (E) Azo-OEt during the 420-nm light irradiation. The arrows indicate the test order. IR thermal images of (F) Azo-Cl and (G) Azo-OEt under the 420-nm light irradiation. The insets show the samples before the light irradiation. The number in the upper right corner of each figure indicates the highest temperature of the materials. Temperature-time curves of (H) Azo-Cl and (I) Azo-OEt during heat release. ΔT represents the temperature difference before and after heat release.