Synthesis and characterization of electrically conducting copolymers based on benzene and biphenyl

Poly(p-phenylene) (H-PPP), which is one of the firstly investigated conducting polymer, has the disadvantage of difficult processability because it is infusible and insoluble. The use of biphenyl instead of benzene leads to ortho-, meta-, para-polyphenylenes which are more soluble and easier to be processed, however their electrical conductivity is lower. Copolymers of polyphenylenes (C-1 and C-2) and corresponding homopolymers (H-PPP and H-PP) were produced by the oxidative cationic polymerization of benzene and/or biphenyl. The soluble (-S) and the insoluble (-I) in chlorobenzene polyphenylenes were separated (H-PP-I, H-PP-S, C-1-I, C-1-S, C-2-I, and C-2-S) and they were doped with a solution Of FeCl3. All polyphenylenes were studied by FTIR, XRD, TGA, and their electrical conductivity with constant current was determined. Pronounced differences between the copolymers and the homopolymers were observed, indicating, the different structure of the former. The values Of the electrical conductivity of doped insoluble copolymers (10(-4) and 10(-5) S/cm) are between that of H-PPP (10(-3) S/cm) and H-PP-I (10(-6) S/Cm). The values of the electrical conductivity of doped soluble copolymers (10(-5) S/cm) are considerably higher than that of H-PP-S (10(-9) S/cm). The new electrically conductive polyphenylenes that were produced differ significantly from the corresponding homopolymers and combine good electrical conductivity and solubility. (C) 2008 Wiley Periodicals, Inc.