偶氮苯改性聚乙烯醇的研究

通过三聚氯氰的氯原子和聚乙烯醇的羟基之间脱氯化氢的反应,用含有2个偶氮苯的三聚氯氰衍生物改性聚乙烯醇（PVA）1788。红外光谱和核磁共振分析表明,在二氧六环和水混合溶剂中可以将偶氮苯成功接枝到PVA上,PVA中约每12个羟基就有1个发生反应。含有偶氮苯的PVA可以溶解在水和二甲亚砜中。其紫外可见吸收光谱与偶氮苯相似,并表现出偶氮苯的典型光致异构现象。     

Preparation of a photoresponsive molecularly imprinted polymer containing fluorine-substituted azobenzene chromophores

The primary objective of this work is to explore the photoresponsive molecular recognition directed by fluorine-fluorine interaction. A new kind of fluorine-substituted photoresponsive functional monomer, (4-methacryloyloxy) nonafluoroazobenzene (MANFAB), was designed and synthesized, and a photoresponsive molecularly imprinted polymer containing a fluorine-substituted azobenzene chromophore (MIPF) was then fabricated using MANFAB as the monomer and 2,3,4,5,7,8,9,10-octafluorophenazine (PAF) as the model template. The photoisomerization process of MIPF materials is reversible. The release and uptake of PAF from toluene is photoregulated by alternate irradiation at 315 nm and 440 nm, indicating that photoresponsive molecular recognition directed by fluorine-fluorine interaction is possible. The binding strength of the imprinted receptor sites in MIPF for PAF is 4.67 × 10⁴ M⁻¹. The density of receptor sites in the MIPF material is 1.26 μmol/g-MIPF.     

The synthesis of aminoazobenzenes and the effect of intermolecular hydrogen bonding on their photoisomerization

Two series of azobenzene derivatives were synthesized so as to investigate the effects of intermolecular hydrogen bonding on their photochemistry. Photoisomerization in polymer matrices was investigated under various irradiation conditions using UV pulsed laser light. Rate constants were calculated according to equations for reversible photoisomerization. Although aminoazobenzenes exhibited faster photoisomerization and larger integral rate constants than the corresponding acetylamino derivatives, the latter compounds displayed faster conversion from the trans to the cis form owing to potential intermolecular hydrogen bonding interaction between the acetylamino groups. Long alkyl chain azobenzenes possessed faster photoisomerization rates than those with short alkyl chains.     

DNA-lipid complexes carrying azobenzene moieties: Preparation, characterization, and photoisomerization

Novel DNA-lipid complexes carrying azobenzene moieties were prepared by substituting sodium counter cations with cationic amphiphilic lipids, namely lipid(AZO) and lipid(diAZO), in which the actual molar ratios of phosphate to lipid were 1:1.05 and 1:1.02, respectively. DNA-lipid(AZO) and DNA-lipid(diAZO) complexes were soluble in common organic solvents including CHCl₃, CH₂Cl₂, methanol, and ethanol, while insoluble in THF, toluene, and water. CD spectroscopy revealed that DNA-lipid(AZO) and DNA-lipid(diAZO) complexes took a predominantly double helical structure in methanol and CHCl₃ and that the helical structure was fairly stable against heating. The trans-azobenzene of the DNA-lipid complexes in the side chain isomerized into cis upon UV irradiation, while the helical conformation of DNA backbone hardly changed. The cis-azobenzene moiety reisomerized into trans upon visible-light irradiation, but they did not recover completely the original geometry of azobenzene moieties in the side chain. Both DNA-lipid(AZO) and DNA-lipid(diAZO) exhibited lyotropic LC properties. The onset temperatures of weight loss of DNA-lipid(AZO) and DNA-lipid(diAZO) were both 226 °C according to TGA in air.     

二卤代乙腈和异二卤代乙腈分子结构、振动光谱和电子光谱的密度泛函研究

采用密度泛函量子化学计算方法获得了在RPA//B3LYP/6-311G(d,p)的理论水平上的二卤代乙腈和异二卤代乙腈的平衡几何构型、振动光谱和电子跃迁能.与已报道的异二碘甲烷和异二溴甲烷的结果比较后得出,异二碘甲烷和异二溴甲烷中的氢原子被吸电子的CN基取代后,形成的异二卤代乙腈分子变得相对稳定,它们的电子吸收光谱比异二卤代甲烷的进一步红移.表明从能量角度上二卤代乙腈比二卤代甲烷更易发生光异构化.从而探讨了吸电子取代基对多卤代甲烷光异构化反应所起的重要作用.     

Electrochemical and optical properties of new soluble dithienylpyrroles based on azo dyes

Two dithienylpyrroles based on azo dyes, namely 2,5′-dimethyl-[4-(2,5-di-thiophen-2-yl-pyrrol-1-yl)-phenyl]azobenzene (SNS-AB2) and 2,5′-dimethyloxy-[4-(2,5-di-thiophen-2-yl-pyrrol-1-yl)-phenyl]azobenzene (SNS-AB3), were synthesized and their corresponding polymers (PSNS-AB2 and PSNS-AB3) were successfully obtained via electropolymerization. The monomers have lower oxidation potentials (0.75 V and 0.80 V vs. Ag/AgCl for SNS-AB2 and SNS-AB3, respectively) when compared to their analogous. Both monomers exhibited photoisomerism properties under irradiation at 360 nm. During the irradiation process, for example, the color of SNS-AB3 changes from yellow to greenish yellow. The electroactive polymer films have well defined and reversible redox couples with a good cycle stability in both aqueous and organic solutions. The polymer films also exhibited electrochromic behaviors; color changes from yellowish green to dark green for the PSNS-AB2 (λ_max = 435 nm and E_g = 2.31 eV) and from mustard color to green for PSNS-AB3 (λ_max = 430 nm and E_g = 2.34 eV). Furthermore, the soluble polymers demonstrated different hues of yellow and green colors.     

All fiber-optic sensing of light using side-polished fiber overlaid with photoresponsive liquid crystals

This study presents a highly sensitive, all-fiber sensor for in situ detecting light. A fiber-optic light sensing platform was created by overlaying an in-line side-polished fiber (SPF) with a photoresponsive liquid crystal (P-LC) consisting of an azobenzene dye, a chiral dopant, and a nematic LC. The resulting P-LC overlaid SPF light sensor is sensitive to three different light sources, including 380 nm light emitting diode (LED), mercury lamp, and office ceiling lights. Under the light illumination, the energy of irradiation from short wavelengths of light (<450 nm) initiates the trans-to-cis photoisomerization of azobenzene. The photochemical LC-phase transition induced by the generated cis-moiety of azobenzene changes the refractive index of LC-overlaid side-polished area. Light illumination increased the attenuation of the input laser signal. After turning off the illumination, the attenuation returned to its original value, allowing the fiber-optic light sensor to be reused. The sensitivity of the resulting fiber-optic light sensor was 0.16 dB/(μW/cm²) with a detection limit of 5 μW/cm² and 0.06 dB/lx with a detection limit of 45 lx when a 380 nm LED and office ceiling lights were used as illumination sources, respectively. The detection limit increased from 45 to 12 lx when P-LC containing 20 wt% azobenzene was used as light sensing material. The proposed fiber-based light sensor has potential use in harsh environments, such as severely humid and corrosive environments, which could damage mechanical and electronic light sensors.