Absorbance shift, conducting polymer

The carbazole group absorbs light in the UV range. Therefore, polymers of this type can become photo-conductive as such only in the UV range. However, colored sensihzers can be added to shift the photoconduchvity into the visible region. 

Analogous to PTs, pyrrole polymers have been polymerized from the dimer with similar results. For example, poly(JV,JV -dimethyl-2,2 -bipyrrole), poly(NNDMBP) (24) exhibits a blue-shifted onset of absorbance of the neutral polymers [94-96]. This results in an increased visible region transparency of the film in the neutral state. The polymer is pale, transmissive yellow in the neutral state and switches to gray-blue when oxidized. In addition, the dimer oxidizes at a lower oxidation potential and the resulting polymer film has an increased conductivity over that produced from the monomer. 

Electrosynthesized polymers of TV-methylpyrrole (NMPy) and A -methylpyrrole-2,6-dimethyl-P-cyclodextrin (NMPy P-DMCD) were characterized with cyclic voltammetry and in situ conductivity measurements in aqueous and nonaqueous solutions [23]. In situ UV-vis-spectra of PNMPy and poly(NMPy-P-DMCD) films show differences both in band absorbances and in energies of polaronic transitions. SUght positive potential shifts are observed for poly(NMPy-P-DMCD) in aqueous and nonaqueous solutions compared to PNMPy films. This observation may be a result of the hydrophobic monomer NMPy, partly or entirely included in the CD s hydrophobic cavity. The results of in situ conductivity measurement for films in this investigation indicate that the resistivity of films that prepared in nonaqueous solution in acetonitrile + LiC104 are lower than resistivity of films prepared in LiC104 aqueous solution by approximately an order of magnitude. 

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