Photoconductive chromophores

The TDHF approximation has been employed in conjunction with the PM3 semi-empirical formalism in work by Kim et on the /S-hyperpolarizabilities of photoconductive chromophores. It was noted that the optical non-linearities of dipolar photoconductive molecules with carbazole, indole or indoline as donor units are large enough to be useful in electro-optic and photorefractive applications. 

The use of low molar mass thermotropic nematic liquid crystals to orient photoconductive chromophores by a guest-host mechanism. 

The use of a liquid crystalline polymer containing photoconductive chromophores which can be brought into a stacked array by alignment of the liquid crystal. 

The Use of Low Molar Mass Thermotropic Liquid Crystals to Orient Photoconductive Chromophores by a Guest-Host Mechanism ... 

The Use of a Liquid Crystalline Polymer Containing Photoconductive Chromophores Which Can be Brought into a Stacked Array by Alignment of the Liquid Crystal... 

Recently photorefractivity in photoconductive polymers has been demonstrated (92—94). The second-order nonlinearity is obtained by poling the polymer doped with a nonlinear chromophore. Such a polymer may or may not be a good photoconductor. Usually sensitizers have to be added to enhance the charge-generation efficiency. The sensitizer function of fuUerene in a photorefractive polymer has been demonstrated (93). 

Postcolumn photochemical reactions are another approach to the detection problem. High-intensity UV light, generally provided by a Hg or Zn lamp, photolyzes the HPLC effluent, which passes through a Teflon (47) or quartz tube. The photolysis reaction determines the nature of the subsequent detection. If the compound has a UV chromophore, such as an aromatic ring, and an ionizable heteroatom, such as chlorine, then the products of the reaction can be detected conductometrically. Busch et al. (48) have examined more than 40 environmental pollutants for applicability to detection with photolysis and conductance detection. Haeberer and Scott (49) found the photoconductivity approach superior to precolumn derivatization for the determination of nitrosoamines in water and waste water. The primary limitation of this detection approach results from the inability to use mobile phases that contain ionic modifiers, that is, buffers and... 

Polyimides carrying NLO chromophores are synthesized. The materials exhibit high Tg ( 220°C). The photoconductivity of polyimide Vin (Scheme 7) is determined to be 1.1 x 10-12 cm/(f2W) under an external field of 150 V/p,m at X = 690 nm and I = 5.9 mW/cm2. After the sample is corona poled, an optical gain coefficient of 22.2 cm-1 under zero field conditions is detected. Polyimide IX exhibits an optical gain of 15 cm-1, which is very close to the optical loss (17.6 cm-1). 

Considerable effort has been expended upon investigating the electronic absorption and fluorescence properties of carbazole derivatives or molecules containing a carbazole moiety/substructure, due to the interest of these compounds for application as nonlinear optical chromophores and as photoconducting materials. In the following, selection of papers is guided mainly by criteria of structural relevance, omitting very bulky molecules in which the carbazole unit is not prominent, or studies of luminescence properties. An overview of the electronic absorption spectra of carbazole derivatives is provided in Table 24. 

Reaction of indole with l,3-dioxolan-2-one leads to 2-(l//-indol-l-yl)-l-ethanol 134 (Equation 24) <2001PLM3023>. Indole 134 was used in the synthesis of a photoconducting nonlinear optical chromophore, 2-[3-(6-nitro-l,3-benzoxazol-2-yl)-lf/-indol-l-yl]-l-ethanol. 

In the photorefractive polymer composites described above, the value of the glass transition temperature is of great importance because it needs to be in a range where the electro-active chromophores can be reoriented by the photorefractive space-charge charge field. Adjustment of Tg is done though the addition of a plasticizer. Examples of plasticizers are shown in Fig. 23. As for the polymer matrixes, plasticizers can be photoconducting or inert. ECZ (molecule (a) in Fig. 23) is widely used with PVK. Inert plasticizers such as BBP (molecule (c) in Fig. 23) have also been combined with PVK [86]. 

Some polymeric systems which open up other areas of general photophysical interest include an examination of the properties of photoconducting polymers with the two pendant chromophores,... 

Very recently, the first metathesis reaction was utilized to synthesize a new type of photorefractive polymers, based on poly(1.6-heptadiyne) derivatives, that contain both a carbazole moiety as a hole transporter and NLO chromophores. attached to TT-conjugated backbones. Photorefractive polymers based on the previous works for the photoconductivity of poly(1.6-heptadiyne) derivatives containing a carbazole moiety and electrooptic activity of poly(1.6-heptadiyne) derivatives containing NLO chromophores were developed.Herein, all functional groups are covalently linked to the polymer backbone. 

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