Soluble high molecular weight poly(p-phenylene) (PPP), in the form of a charge-transfer complex, was synthesized by complete dehydrogenation of poly(I 3-cyclohexadiene) (PCHD) with excess tetrachloro-1,2(o)-benzoquinone (TOQ). The yield of the PPP-TOQ complex increased as the molecular weight of the original PCHD increased. The addition of TOQ to. the PPP polymer chain occurred mainly at the 1,4-phenylene (Ph) units. The PPP-TOQ complex showed good solubility in tetrahydrofuran; the solubility was not limited by the length of the 1,4-Ph sequence. The formation of the PPP-TOQ complex effectively suppressed crystallization of PPP due to the decrease in pi-pi intermolecular interactions in the PPP molecules, and had a significant effect on pi-orbital conjugation in PPP.