Synthesis and properties of conjugated polymers from 3,6-di(4-chlorophenyl)-3,6-dihydrophthalic acid diethyl ester and application to the photo-sensitizer of a solar cell

Abstract

Ni(0)-catalyzed coupling polymerizations of 3,6-di(4-chlorophenyl)-3,6-dihydrophthalic acid diethyl ester 1 were accompanied by isomerization of the 1,4-cyclohexadiene moiety into a 3,5-cyclohexadiene group, yielding a conjugated polymer. The structure of this conjugated polymer was the same as that of the conjugated polymer from 3,6-di(4-chlorophenyl)-1,2-dihydrophthalic acid diethyl ester 2. The number-average degree of polymerization was only ∼7 due to the low solubility of the conjugated polymer. The conjugated polymer exhibited a λ max at 430 nm in the absorption spectrum, and could be applied as a photo-sensitizer of a solar cell. The incident monochromatic photon (450 nm)-to-current conversion efficiencies of photocurrent from an indium-titanium oxide (ITO)/TiO2 electrode modified with the conjugated polymer was 6.1% in the I3−-3I− electrolyte wet system. The conjugated polymer exhibited a glass transition temperature of 210 °C and was converted by thermal treatment at 300 °C to poly(p-phenylene) (PPP) with the elimination of ethoxycarbonyl groups. Ni(0)-catalyzed coupling polymerizations of 3,6-di(4-chlorophenyl)-3,6-dihydrophthalic acid diethyl ester 1 were accompanied by isomerization of the 1,4-cyclohexadiene moiety into a 3,5-cyclohexadiene group, yielding a conjugated polymer. The structure of this conjugated polymer was the same as that of the conjugated polymer from 3,6-di(4-chlorophenyl)-1,2-dihydrophthalic acid diethyl ester 2. The conjugated polymer exhibited a λ max at 430 nm in the absorption spectrum, and could be applied as a photo-sensitizer of a solar cell. The incident monochromatic photon (450 nm)-to-current conversion efficiencies of photocurrent from an ITO/TiO2 electrode modified with the conjugated polymer was 6.1% in the I3--3I- electrolyte wet system.