Preparation and properties of polymers with biphenyl units in the chain: Syntheses of solvent‐soluble substituted polyphenylenes

Benzidinetetrazonium chloride (BTC)–CuCl and BTC–FeCl 2 complexes were thermally converted to benzene‐soluble poly‐4,4′‐biphenylene plus small amounts of insoluble material. The soluble fraction was more stable than the insoluble fraction when heated at 300–500°C, although the solubility decreased. BTC in water was converted to an insoluble material by addition of alkali or cuprous ammonia solution. The C/(H + Cl) ratio indicated the existence of three to five side groups for each twenty phenyl groups of the insoluble fraction, while that of the soluble fraction showed few such groups. The number increased to one or more side groups for each phenyl nucleus as both soluble and insoluble fractions were heated to 500°C. A thin film of soluble fraction deposited on a copper plate showed an electrical conductivity in the range 10 −2 –10 −3 ohm −1 cm −1 at 25°C and an energy gap (Δ E g ) of 0.2–0.3 eV. However, a compressed specimen of the same soluble fraction showed little conductivity. Solventsoluble samples of substituted poly‐4,4,‐biphenylene were prepared by the same procedure. These materials cracked on processing, and accurate conductivity measurements could not be made.