Synthesis and Photochromic Behavior of Azo-Polydiphenylsilanes

This work presents the influence of the trans–cis photoisomerization process of azobenzene-segments onto the optical properties of polysilanes. For this purpose 4-(phenyldiazenyl)phenol and 4-[(4′-nitrophenyl)diazenyl]phenol groups were attached to poly[diphenylsilane-co-methyl(bromopropyl)silane] using the Williamson etherification conditions. Photoisomerization of the pendant azo-groups by irradiation with 365 nm UV light induced distortion of the polysilane backbone conformation in a reversible manner. This process was studied by UV spectral analysis and the photochromic behavior of both polymers was established by taking into account the variation of the σ–σ* absorption intensity.     

光学活性偶氮苯自组装膜的研究进展

目前,材料的研究越来越朝着精密可控的方向发展,对外场敏感材料的研究日益成为研究的热点.偶氮苯及其衍生物具有在紫外-可见光照射下发生可逆光致异构化的特性,因而偶氮苯类敏感膜材料的研究日益成为研究的热点.首先介绍偶氮苯分子光致异构现象及异构化过程中性能的变化,然后详细阐述了影响偶氮苯分子光致速率的诸多因素,最后综述了国内外...     

Synthesis, thermal and photochemical properties of liquid crystalline telomers

Liquid crystalline telomers have been synthesized by free radical polymerization. Their thermal as well as photoresponsive properties are reported. The effects of telogen content on the degree of polymerization were also studied. The degree of polymerization decreased with an increase in the telogen content during telomerization. Consequently, the molecular weights of the telomers decreased with the increase in the telogen content. The isotropization temperatures of the telomers from liquid crystalline to isotropic phase were determined as a measure of stability of the telomers. The stability of the telomers was found to be influenced strongly by their molecular weight and structure of the telogen. The telomers also showed fast photoresponsive properties due to the disorganization of the uniaxial molecular orientation caused by the trans-cis photoisomerization of the azobenzene groups.     

Effect of α-Cyclodextrin on the Photoisomerization of Azobenzene Functionalized Hydroxypropyl Methylcellulose in Aqueous Solution

Summary The effect of α-cyclodextrin (α-CD) on the trans-cis photoisomerization of an azobenzene functionalized polymer (AZO-HPMC) in aqueous solutions has been systematically studied. It has been shown that the cis fraction at the photostationary states and the photoisomerization rate constant increases with increasing α-CD concentration, indicating that the trans-cis photoisomerization of AZO-HPMC is accelerated by addition of α-CD. This behavior is interpreted in terms of the aggregation between the azobenzene groups. The formation of inclusion complexes between the trans isomers and α-CD inhibits the aggregation and consequently increases the mobility and free volume for the isomerization.     

Photoisomerization of amphiphilic azobenzene derivatives in Langmuir Blodgett films prepared as polyion complexes, using ionic polymers

Polyion complexation in mixed Langmuir and Langmuir Blodgett (LB) films of photochromic amphiphilic azobenzene carboxylic acids, 11-[4-(4-hexylphenyl)azo] phenoxyundecanoic acid, 11-(4-phenylazo)phenoxyundecanoic acid, and diamine grafted poly(methylmethaacrylate) polymers has been studied. Monolayer behaviour of the pure components and mixed films was studied through pressure–area isotherms and LB films were characterized by spectroscopic, X-ray diffraction and Atomic force microscopy techniques. Aggregation (H-type), often observed in LB films of pure amphiphilic azo acids, was partly avoided in the mixed LB films as indicated by absorption spectral studies. Photoisomerization of the polyion complexed LB films was also studied. The results altogether demonstrate that amine grafted polymer enter into a polyion complexation with azo acid carboxylate group. LB films could be obtained by transfer of the composite monolayers and these LB films exhibited different levels of aggregation of the azo acids. Reversible photoisomerization was observed in LB films with unaggregated azo acid.     

Polymers Move in Response to Light

Significant advances have recently been made in the development of functional polymers that are able to undergo light‐induced shape changes. The main challenge in the development of such polymer systems is the conversion of photoinduced effects at the molecular level to macroscopic movement of working pieces. This article highlights some selected polymer architectures and their tailored functionalization processes. Examples include the contraction and bending of azobenzene‐containing liquid‐crystal elastomers and volume changes in gels. We focus especially on light‐induced shape‐memory polymers. These materials can be deformed and temporarily fixed in a new shape. They only recover their original, permanent shape when irradiated with light of appropriate wavelengths. Using light as a trigger for the shape‐memory effect will extend the applications of shape‐memory polymers, especially in the field of medical devices where triggers other than heat are highly desirable.     

蛋白质光学信息记录材料细菌视紫红质

光敏蛋白质细菌视紫红质(bR)存在于嗜盐菌紫膜中。bR分子吸收光子后,视黄醛构型发生变化,产生一系列中间态并经历一个独特的光循环过程,同时完成质子泵功能。bR具有高的空间分辨率、高的光灵敏度、高的循环次数及良好的热稳定性和非线性光学特性,是一种性能优良的生物光学材料,可广泛应用于空间光调制器、投影显示、全息记录、模式识别、光学信息存储等方面,在分子电子学、生物计算机等领域具有诱人的应用前景。     

Effects of substitution position on electrochemical,electrochromic, optical,and photoresponsive properties of azobenzenecarboxylic acid alkyl ester derivatives

This study aimed to investigate the effects of substitution position on the electrochemical, electrochromic, optical, and photoresponsive properties of azobenzenecarboxylic acid alkyl ester derivatives. Therefore, a series of azobenzenen ester derivatives, including azobenzene-4,4′-dicarboxylic acid dialkyl ester derivatives (ADDEDs), azobenzene-3,3′-dicarboxylic acid dialkyl ester derivatives (ADADEs), and azobenzene-3,3′,5,5′-tetracarboxylic acid four alkyl ester derivatives (ATFAEDs), was synthesized in this work, and their electrochemical, electrochromic, optical, and photoresponsive properties were characterized. Substitution position significantly influenced the electrochemical, electrochromic, and optical properties but not the photoresponsive properties of azobenzenecarboxylic acid alkyl ester derivatives. With regard to stability and response time, the electrochromic properties of azobenzenecarboxylic acid alkyl ester derivatives decreased in the following order: ADDEDs > ATFAEDs > ADADEs. However, ADDEDs, ADADEs, and ATFAEDs can all be reversibly and efficiently photoswitched between trans and cis states upon alternate irradiation at 365 and 440 nm under electrochromic conditions.