Synthesis and electrooptical characterization of polysiloxanes containing indolyl groups acting as photoconductive substrates for photorefractive materials

Abstract Synthesis and electrooptical analysis of polysiloxane and poly-N-vinyl derivatives containing indolyl groups are reported. The indole group and some of its methyl derivatives have been taken into account in order to evaluate their behaviour, with respect to that of the widely employed carbazole group, when used as photoconductive centres attached to a polymer chain. The obtained data show that photoconductivity and traps formation mechanism can be inferred as functions of the physico-chemical parameters (electric dipole moment and ionization potential) of the different groups and polymers involved. To this end such parameters have been carefully computed for a series of pyrrole, indole and carbazole derivatives. The 2,3-dimethylindole derivative appears to be particularly promising due to its electrooptical behaviour in the red absorption region where measurements have been accomplished and are shown to be consistent with the theoretical predictions

Poly(1-vinylindole) and some of its methyl derivatives as substrates for photorefractive materials: their synthesis, optical and electrical characterization

The best conditions for the synthesis of poly(1-vinylindole) (PVI) and some of its methyl derivatives have been investigated. The aim of the research was to verify if PVI could be used instead of poly(1-vinylcarbazole) (PVK) in polymeric blends having photoconductive and/or photorefractive behavior. All synthesized polymers are characterized by a glass transition temperature that is lower than that of PVK. It has been verified that the indole ring system, inclusive of its methyl substituted derivatives, lacking of the symmetry characteristics of carbazole, possesses an electric dipole moment that is constantly higher than that of PVK. A higher dipole moment can be an advantageous feature to improve the solubility within the polymeric matrix of the optically non-linear molecule, necessary for photorefractivity. Charge-transfer complexes with a fluorenone-like photosensitizer are efficiently formed by both PVI and its derivatives. A direct current measuring apparatus has been assembled by which photocurrents of few picoamperes can be detected and recorded. Preliminary reported results clearly show that PVI is a photoconductive material. Its photoconductivity is compared with that of PVK and of hybrid materials containing mixtures of carbazole and indole moieties, present in the measuring cell as pendant groups on a macromolecular chain, as single molecules, or both

The Oxidation of Poly(N-Vinylpyrrole) to Electroconducting Ladder Polymers

A new electroconducting polymer with particle `ladder' structure is prepared by a two-step method consisting of free radical polymerization of N-vinylpyrrole followed by oxidation polymerization of the heteroarom. side chains. The formation of this structure is substantiated by the close similarity between IR spectra of oxidized polymer (I) and of polypyrrole obtained under similar conditions, as well as by the increase of the elec. conductivity from that of an insulator to 10-2 Ω-1 cm-1. Surprisingly, this last value is better than for poly(N-methylpyrrole), which should offer minor steric hindrance both to conjugation and doping. ESR data concerning I treated with different oxidizing agents and conditions are discussed with reference to the possible presence of paramagnetic species. Polymers of oxidized I type, consisting of one hydrocarbon chain paralleled by a conjugated aromatic chain, appear to be of interest for preparing tractable electroconducting materials and for investigating relations between elec. properties and spatial geometry