No abstract

N-Carbazolylacetylene (CzA) was polymerized in the presence of various transition metal catalysts including WCl 6 , MoCl 5 , [Rh(NBD)Cl] 2 , and Fe(acac) 3 to give polymers in good yields. The polymers produced with W catalysts were dark purple solids and soluble in organic solvents such as toluene, chloroform, etc. The highest weight-average molecular weight of poly(CzA) reached about 4 ϫ 10 4 . In the UV-visible spectrum in CHCl 3 , poly(CzA) exhibited an absorption maximum around 550 nm ( max ϭ 4.0 ϫ 10 3 M Ϫ1 cm Ϫ1 ) and the cutoff wavelength was 740 nm, showing a large red shift compared with that of poly(phenylacetylene) [poly(PA)]. Poly(CzA) began to lose weight in TGA under air at 310°C, being thermally more stable than poly(PA) and poly[3-(Ncarbazolyl)-1-propyne]. Poly(CzA) showed a third-order susceptibility of 18 ϫ 10 Ϫ12 esu, which was 2 orders larger than that of poly(PA).

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Anion exchange membranes with viologen moiety containing fine particles of anatase-TiO 2 were prepared by the casting method and photovoltage generation was examined by photoirradiation to one surface of the membrane after assembling the photocell ͓clamping the membrane swollen with ethylene glycol between two indium-tin oxide ͑ITO͒ electrodes͔. Higher photovoltage ͑175 mV, load resistance, 200 k ⍀͒ rapidly generated compared with the membrane without TiO 2 ͑105.7 mV͒. However, the photovoltage was anisotropic concerning the direction of the membrane surfaces due to heterogeneous distribution of the TiO 2 particles across the membrane. Thus, the photocell was examined by assembling the cell composed of the anion exchange membrane with a viologen moiety ͑without TiO 2 ) swollen with ethylene glycol or triethylene glycol and an n-type semiconductor ͑CdS, rutile-TiO 2 , and anatase-TiO 2 ) layer. A photovoltage of more than 350 mV was observed by photoirradiation to the semiconductor layer side. This was due mainly to electrons generated from excited n-type semiconductor, which were collected at the ITO electrode, and due to reduction of the viologen moiety of the membrane at the dark side by the electrons via a load resistance. The formed hole on the semiconductor is thought to migrate through the membrane to the dark side via the solvent by a hopping mechanism and then oxidize reduced viologen moiety at the dark side. A thicker layer rapidly generated higher photovoltage ͑the highest photovoltage, 617 mV͒. Electrons from exited TiO 2 significantly contributed to the photovoltage compared with electrons released from the viologen moiety.