Cationic and radical polymerization of N-vinyl-2-phenylpyrrole: Synthesis of electroconducting, paramagnetic and fluorescent oligomers

Cationic polymerization of N-vinyl-2-phenylpyrrole (catalysts: Me3SiCl, CF3COOH, BF3·OEt2, HCl, WCl6, FeCl3, complex LiBF4-dimethoxyethane, catalysts concentration 1-2 wt%, 20-70 °C, 24-48 h) affords oligomers (molecular weight 1400-1700) of a unexpected structure with alternating 2-phenylpyrrole and ethylydene units, the yields reaching 63%. The oligomers structure has been supported by isolation and identification of the corresponding dimer, N-vinyl-2-phenyl-5-[N-(2-phenyl-1H-pyrrol-1-yl)ethyl]-1H-pyrrole. Radical polymerization of the same monomer (AIBN, 1.5-4 wt%, 60-80 °C, 40-60 h or UV irradiation or both) gives oligomers (molecular weight 2100-3000) of normal structure having polyethene backbone with pendant 2-phenylpyrrole groups in up to 40% yields. The oligomers of both types are semiconductors (1.3 × 10−6-3.6 × 10−6 S/cm) after doping with I2, paramagnetic (4.2 × 1017-8.7 × 1017 g−1) and fluorescent in a near UV region (λ 355-363 nm, acetonitrile).