Papers by Keyword: Photoisomerization

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: The photoisomerization effect on new chalcone derivative is reported. The synthesized chalcone was characterized by different spectral analysis such as ¹H-NMR, ¹³C-NMR, FTIR, LCMS and UV/Vis. It revealed the photoisomerization effect in solution, the E-Z isomerization occurred around 60sec, whereas Z-E isomerism occurred at 0min. This chalcone derivative is more useful in fabrication of permanent optical storage devices.

Abstract: Reversible photoisomerization between the cis and trans isomer of [Ru(OAc)(2mqn)2NO] (H2mqn=2-methyl-8-quinolinol) was studied quantitatively, using 1H Nuclear magnetic resonance (NMR) spectra. The kinetic study showed that the photoisomerization from trans to cis isomer was first-order and the rate constant (k) is 0.014 (min-1) at 420 nm, 0.0034 (min-1) at 550 nm, respectively. The main absorption band in UV-Vis region for cis and trans isomer was observed from 300 nm to 550 nm, the electronic structure of these compounds was performed with DFT (Density functional theory) calculation and was discussed based on HOMO–LUMO analyses. The study provide detail information to design advance optoelectronic materials based on nitrosylruthenium(II) complexes.

Abstract: Mesostructured SiO2 films functionalized with the azo-chromophore Disperse Red 1 were synthesized by sol-gel method. The mesostructured long-range order in the films was determined by X-Ray Diffraction. The azo-chromophores in the films work as nano-impellers through their photo-induced trans-cis reversible isomerization. When the films are doped, they are able to control the release of the dopant by all-optical processes. We used the dye laser Rhodamine 6G as dopant, its very distinctive luminescence around 550 nm allows to follow the release. Polarized green and infrared laser light were used as pump sources to direct the movement of the nano-impellers. 299 nm light was used as a probe to induce the Rhodamine 6G luminescence, which was measured as function of the pumping time with a photomultiplier coupled to a monochromator. The results corresponding to the green and to the infrared pumping sources are compared in order to determine the feasibility to photo-control the nano-impellers movement through a two-photon absorption process.

Abstract: A kind of the ionic bolaform surfactant was synthesized in four steps, with 4-nitrotoluene as raw materials. Firstly, bis-(2-methyl-4-nitrophenyl)-methane (BMNM) was synthesized using paraformaldehyde as a coupling agent; then, bis-(2-methyl-4-aminophenyl) methane BMAM) was obtained through a reduction reaction of BMNM; in the following step, bis-(2-methyl-4-p-hydroxy- azophenyl)methane was prepared through diazotization-coupling reaction; at last, Bolaform surfactant was obtained through a addition reaction of butane sultone and bis-(2-methyl-4-p- hydroxy-azophenyl)methane. The products were characterized by IR and 1HNMR. The surface tension and UV-Vis absorption and fluorescence spectra of aqueous solution of this Bolaform surfactant were tested. The cis/trans photoisomerization of Bolaform surfactants were studied in DMSO solution at 365nm irradiation, which indicate this Bolaform surfactantis photosentive and easily to control surface activity by photoisomerization.

Abstract: Some functional azobenzene derivatives with aromatic substituted groups have been synthesized and their photoisomerization have also been investigated. It has been found that depending on different substituted groups, such as phenyl or naphthyl segments, the formed azobenzene derivatives showed different properties, indicating distinct regulation of molecular skeletons. Spectral data confirmed commonly the characteristic absorption of substituted groups and aromatic segments in molecular structures. In addition, the photoisomerization of all compounds in solution can show trans-to-cis photoisomerization by UV light irradiation, and demonstrate distinct isomerization ratio depending on effect of different substituted headgroups. The difference is mainly attributed to the aromatic substituted headgroups and methyl group in molecular structure. The present results have showed that the special properties of azobenzene derivatives could be effectively turned by modifying molecular structures of objective compounds with proper substituted groups, which show potential application in sensor and functional material field.

Abstract: A novel azobenzene optically polymer (P-DA) was synthesized based on the azo chromophore molecule, chiral reagent L(-)-tartaric acid, acryloyl chloride and methacrylate. The P-DA was characterized by FT-IR, UV-Vis spectroscopy, 1H NMR, DSC and TGA. The P-DA had high thermal stability up to its glass-transition temperature (Tg) of 110 oC and 5 % heat weight loss temperature of 199 oC. The UV-induced trans/cis photoisomerization and reflex-isomerization behaviors were investigated. The results indicated that the P-DA solution could undergo photochromism after irradiated by 365 nm UV light. The optical parameters: refractive index (n), the dielectric constant (ε) and thermal volume expansion coefficient (β) of P-DA were obtained. The thermo-optic coefficients are one order of magnitude larger than those of the inorganic materials, such as SiO2 (1.1×10−5 oC -1 and LiNbO3 (4×10−5 oC -1) and was larger than the organic material such as polystyrene (-1.23×10-4 oC -1) and PMMA (-1.20×10-4 oC -1). The conclusion had a little significance to develop optical communication.