Papers by Keyword: Azobenzene

Abstract: The photoisomerization of azobenzene (Azo) in system can induce changes of adhesion. Using this feature, some significant breakthroughs have been achieved in distinct adhesive systems from small molecular to polymer to supramolecular. Although the mechanisms vary from different situations, photoisomerization and photothermal effect of azobenzene under different irradiation always play significant role in the switch of the adhesion strength. By utilizing these features, some adhesive systems have illustrated promising and competitive performance. This review will concentrate on these achievements and advantages of photocontrolled adhesives based on azobenzene derivatives which are classified by photocontrolled mechanism. Furthermore, we also give some consideration to the future development of photocontrolled adhesives.

Abstract: In the past years, azobenzene, as a common photoreactive group, has been widely used in intelligent photocontrolled supramolecular gels. In the field of biomedicine, a few supramolecular hydrogels based on azobenzene are regarded as carriers with low damage and high control in vivo due to their advantages in light response. In the environmental field, some hydrogels can also adsorb pollutants under the control of light through the interaction between host and guest. At the same time, supramolecular hydrogels based on azobenzene with multiple stimulus responses have been studied. It is difficult for most supramolecular organogels to have multiple stimulus responses simultaneously and the preparation conditions are also more complex. In this paper, I have summarized the latest research results of supramolecular hydrogels and organogels based on azobenzene in recent years so that researchers can have a deeper understanding of the preparation methods, properties and application of the supramolecular gels containing azobenzene.

Abstract: We have synthesized polyester type dendrimers containing azobenzene chromophore in the core and trityl groups at the periphery using divergent growth strategy up to 3^rd generation. We analyzed dendrimer samples using NMR, HPLC, TG, DSC and UV-Vis techniques. We found out that functionalization of dendrimer periphery is not complete. Dendrimers with trityl groups at the periphery have glass transition temperatures in the range 73-87 °C.

Abstract: The effect of the introduction of a CF₃ group to a silyl-anchor moiety of the sensitizer on the sensitizing property for the dye-sensitized solar cell was examined by using alkoxysilyl-anchor azobenzene dyes. The cell sensitized by the silyl-anchor dye with the electron-withdrawing CF₃ group in the silyl-anchor moiety exhibited higher photovoltaic performance than that by the silyl-anchor dye without the CF₃ group.

Abstract: Allylsilyl and hydrosilyl groups were examined as the anchor moieties of sensitizing dyes for dye-sensitized solar cells by using silylazobenzene dyes. Allylsilyl and hydrosilyl dyes were observed to adsorb efficiently onto TiO₂ electrodes and the dye-adsorbed electrodes exhibited high durability to water. Light-to-electric energy conversions were also confirmed in the cells using the dye-adsorbed electrodes. The results show a high potential of allylsilyl and hydrosilyl dyes as the sensitizing dyes.

Abstract: An novel nonlinear optical alkynyl substituted azobenzene 4-(propargyl methyl ester)-4'-[(N, N'-diethyl) amino] azobenzene was synthesized and characterized by FTIR, ¹HNMR. The linear optical properties were investigated by UV-Vis spectra. The nonlinear optical properties and optical limiting properties were investigated using 21 ps pulse at 532nm and 4ns pulse at 532nm, respectively. The results show that this novel nonlinear optical alkynyl substituted azobenzene possesses large third nonlinear optical coefficient and good optical limiting properties.

Abstract: In dye-sensitized solar cells (DSSCs) fabricated with azobenzene and azulene derivatives as the photosensitizing dyes, the replacement of the conventional I₃^-/I^- redox mediator with Br₃^-/Br^- redox mediator possessing more positive redox potential has been examined to improve open-circuit photovoltages (V_oc) of the cells. The cells with the Br₃^-/Br^- redox mediator exhibited high V_oc of ~0.8 V, resulting in higher light-to-electric energy conversion efficiencies (η) than the cells with the I₃^-/I^- redox mediator by a factor of 1.7 under the simulated sunlight irradiation (AM-1.5G, 100 mW cm^-2). The results indicate a high potential of the Br₃^-/Br^- redox mediator in DSSCs.

Abstract: A series of new azobenzene side chain liquid crystalline polymers were synthesized by two different azo mesogen monomers, 4-((4-(ethoxycarbonyl) phenyl) diazenyl) phenyl 4-(allyloxy) benzoate (M₁) and (4-((4-(ethoxycarbonyl) phenyl) diazenyl) phenoxy) methyl acetyl 4-(allyloxy) benzoate (M₂). All polymers (P₁~P₈) were synthesized by graft polymerization using polymethyl hydrosiloxane as backbone. Their chemical structures were confirmed by FTIR and ¹HNMR spectra. The mesomorphic properties and phase behavior were investigated by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and thermogravimetric analyzer (TG) measurements. The results showed that P₁~P₈ exhibited thermotropic liquid crystalline properties and revealed nematic thread texture with wide mesophase temperature ranges. The temperatures when 5% weight loss occurred were higher than 305°C, which declared that the synthesized azobenzene liquid crystalline polymers had a high thermal stability.

Abstract: A novel nonlinear optical active triazine dye 2-(4-methyl-4-amino-azobenzene )-4-sodium sulfanilate-6-chloro-1,3,5-triazine was synthesized by condensation reaction and characterized by FTIR, ¹HNMR, respectively. Their nonlinear optical properties were investigated using 5 ns pulse at 532 nm, which showed excellent nonlinear optical property.

Abstract: Liquid crystalline polymer (LCP) and the copolymer of LCOand Pendant Polyhedral Oligomeric Silsequioxanes (LCP-POSS) showed the first-order photoisomerization reaction. As compared with LCP, the photoisomerization rate constant of LCP-POSS decreased a little. With a higher thermal stability and more stable LC behavior as well as a little decreased photoisomerization rate constant, the incorporation of POSS to azobenzene liquid crystalline polymers may have significant sense and will definitely play a key role in developing novel high-performance optic and photonic nanodevices.