Carbazole groups

Providing an ion exchanger with a sufficient number of redox groups so that conduction can occur by a relay-type redox-change mechanism. Examples are hydroquinone-derived redox polymers and polyvinyl polymers with a tetrathia-fulvalene, ferrocene, or carbazole group, which have been found useful for research and analytical applications. 

Y. Fu, J. Li, S. Yan, and Z. Bo, High molecular weight dendronized poly(fluorene)s with peripheral carbazole groups synthesis, characterization, and properties, Macromolecules, 37 6395-6400, 2004. 

While P. V.23 is used in considerable volume, P.V.37 is a specialty product. Pigments of the P.V.34 and 35 type, which are much inferior in terms of tinctorial strength and sometimes also migration fastness, especially in plastics, have been discontinued several years ago. These compounds typically contained ethoxyani-line with acetylamino or benzoylamino moieties instead of the carbazole group of P.V.23 [7-9],... 

The filled upper and free lower orbitals in PVC belong to the carbazole groups. So one can consider PVC as a disordered organic medium. The side chromophore groups play the role of traps for hopping charge carrier transport. 

Electron or hole nature of the charge transfer may be realized in PVC-TNF Cl complexes depending on the concentration of the components [54]. The contribution of holes and electrons in conductivity is equal at the PVC-TNF ratio 1 1. Gill s experimental data for mobilities is shown in Fig. 10. The sharp concentration decrease of the neutral, noncoupled complex carbazole groups, leads to the fast decrease of the hole mobility. The electron mobility increase with increase of the TNF content was also accompanied by an increase of the... 

Fig. 10. Dependence of the charge carrier mobilities in PVC-TNF [54] a electrons (1) and holes (2) versus molar concentrations of the TNF-PVC at the electric field strength 10s V-cm 1. b holes versus mean distance r between nonbound in complex carbazole groups...

Okamoto et al. (1973,1973a, 1973b) measured photogeneration efficiencies of PVK. The results were explained by the field-assisted thermal dissociation of an exciplex formed between an excited carbazole group and an acceptor impurity. Okamoto et al. (1975) measured the efficiencies of /3-N-caibazolyl-ethyl vinyl ether, an oligomer of N-vinylcaibazole, and PVK. The efficiencies of the three compounds were comparable. The results were described by the dissociation of singlet excitons. 

Effects of bromination on hole transport in PVK were described by Griffiths et al. (1977). The Br substitution appeared randomly in the 3 or 6 positions of the carbazole group. For both PVK and Br-PVK, the mobilities varied with field as logn Relative to PVK, the mobility of Br-PVK was reduced... 

Schnorer et al. (1988) measured hole mobilities of polysiloxane with pendant carbazole groups separated by three methylene units from the backbone. At 2.0 x 10 V/cm, the mobility decreased from 9.8 to 2.4 x 10-7 cm2/Vs as the thickness increased from 3 to 40 pm. The results were described by the Scher-... 

Jt OLYSILOXANES WITH PENDANT SIDE CHAINS are interesting materials from both the theoretical and practical points of view. A number of polysiloxanes with various side chains, such as liquid crystals (i, 2), carbazole groups (3), electron-donor and electron-acceptor groups (4), polystyrene (5), and functional groups (hydroxyl or carboxyl) (6), have been synthesized. Polysiloxanes are known for their useful properties, which include flexibility, heat resistance, water repellence, and biological inertness. These properties, combined with the ease with which a tailored polymer structure can be prepared,... 

Initially, the ability of PVK to transport charges was assumed to be related to the spatially crowded structure of PVK (7), in which the carbazole groups, because of their covalent-bonding backbone, are forced to interact with each other to the point that significant orbital overlap creates a band structure. However, the observed mobilities were low cm /V-s),... 

Mobility Scales with Average Inter site Hopping Distance, Gill identified an exponential dependence of electron drift mobility on average TNF intersite hopping distance and noted an associated decrease in hole drift mobility (35). Gilfs subsidiary observation that TNF addition also decreased hole mobility precisely because complexed carbazole is removed as a hole transport site provided evidence for the key role of the discrete carbazole groups in hole transport. 

Overall, these results demonstrate that the chlorination reaction differs markedly from bromination and seems to be restricted to the carbazole groups. Although the sample appears to be homogeneous by electron microscopy, the simultaneous appearance of aromatic and non-aromatic sidegroup resonances in the reacted polymer is difficult to explain without invoking sample heterogeneity. 

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