Copolymers from bithiophene/pyrrole

Photoluminescence spectra of copolymer of pyrrole and bithiophene films whose thiophene content is higher than 50% consist of three peaks around 2.0, 1.8, 1.7eV corresponding to phonon side bands, at lOK. These peaks have been considered to be radiative relaxation from self-trapped exciton levels. The peak at the highest energy reflects band gap. 

Cyclic voltammetry of the copolymer shows three anodic peaks, two matching the oxidation potentials of the parent homopolymers and a third which is intermediate. Authors attributed the data to the formation of blocks of polypyrrole and polythiophene cormected by blocks of random alternating groups of pyrrole and bithiophene. Increasing the amount of bithiophene in the copolymer produced a strong drop in the final conductivity of the materials, from 17 S cm at 1 mol% to I S cm at 14 mol%. 

Fine metal particles coated with PT are protected from oxidation and have improved handling properties [820]. Electrical conductors with good heat and moisture resistance (no discoloration) contain copper powder and 0.5% powder [821]. The electrochemical oxidation of hydrogen, formic acid, and methanol is possible on an active electrode with a small amount of platinum dispersed into a pyrrole/bithiophene copolymer as matrix [822] or on Pt-Sn catalysts electrodeposited on a PMT [823]. The reduction of tetracyanoquino-dimethane and chloranil at a PMT coated glassy carbon electrode is possible [824]. CO2 molecules can be converted to salicylic add derivatives by photoirradiation in the presence of phenol derivatives and PHT in ethanol. PHT acts as a photocatalyst on irradiation with visible light, and the luminescence is quenched by both CO2 gas and phenol molecules (cf. Sect. 3.5) [367]. 

Copolymers of pyrrole and 2,2 -bithiophene were prepared by electropolymerization using mixed monomer-containing nonaque-ous electrolyte solutions by Peters and van Dyke [729]. CVs of the polymer film showed three oxidation peaks. Two could be matched with the corresponding oxidation peaks of the homopolymers the third (in between) may be caused by a random copolymer. Based on supporting evidence obtained from in situ UV-vis spectra, three distinct redox couples could be identified. Two were assigned to short blocks of PPy and poly(2,2 -bithiophene) the third was assigned to the mentioned copol3mer. Electric conductivity was lower like for pure PPy. 

Catalytical activities have been claimed for copolymers arising from pyrrole and bithiophene with a small amount of dispersed platinum to be effective in the electrochemical oxidation of hydrogen, formic acid and methanol [245] the same catalytic effect was found for electrodes of 3-methyIPT with electrochemically deposited platinum and tin [246]. The reduction of tetracyano-p-quinodimethane and chloranil can be achieved at a glassy carbon electrode coated with 3-methylPT [247]. Phenol derivatives and carbon dioxide can be converted to salicylic acid derivatives on 3-hexylPT electrodes under irradiation in ethanolic solution [248]. This electrode material acts as a photocatalyst on irradiation with visible light, the luminescence is quenched by carbon dioxide as well as phenol. 

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