Photoconductivity of substituted polyacetylenes

Photoconduction under visible light illumination is investigated using xerographic discharge technique in the photoreceptors of the following substituted polyacetylenes: [BOND][HC[DOUBLE BOND]C(C6H5-p-R)]n[BOND], [BOND][HC[DOUBLE BOND]C(3-C4H2S-β-R′)]n[BOND], and [BOND]{HC[DOUBLE BOND]C[(CH2)m-R″]}n[BOND], where R = CH3 (2), CO2(CH2)6OCO-Biph-OC7H15 (Biph = 4,4′-biphenylyl; 3); R′ = Si(CH3)3 (4), Br (5); and R″ [DOUBLE BOND]CO2(CH2)6OCO-Biph-OC9H19 (m = 2; 6), 9-carbazolyl (m = 3; 7), OCO-Biph-OC7H15 (m = 9; 8). In the undoped state, 2–4 and 6–8 show much higher photosensitivity than poly(phenylacetylene)(R = H; 1). The polyacetylenes with electron-donating and/or hole-transporting substituents perform better than do those with electron-accepting ones. The liquid crystalline polyacetylene 6 exhibits very high photosensitivity, probably because of the crystalline aggregates of its mesogenic pendants. C60 acts as a photoconductivity enhancer when doped to amorphous 3 but functions as a quencher when mixed with liquid crystalline 6. While 3 shows low photosensitivity in the undoped state, doping with I2 and sensitization with crystal violet dramatically increase its photosensitivity up to 41.2 × 10−3 lx−1 sec−1.