PREPARATION OF POLY(P-PHENYLENE) VIA A NEW PRECURSOR ROUTE

Methyl 2,5-dichlorobenzoate (1) was polymerized in dimethylformamide with a catalyst system comprised of nickel(II) bromide, triphenylphosphine, and zinc to produce poly[2- (methoxycarbonyl)phenylene-1,4-diyl] (2). The GPC measurements indicated that the molecular weight distribution of 2 was monomodal and the degree of polymerization was around 100. The hydrolysis of 2 yielded poly(2-carboxyphenylene-1,4-diyl) (3). Polymer 3 was soluble in quinoline and pyridine as well as aqueous sodium hydroxide. The catalytic decarboxylation of 3 produced poly(p-phenylene) (PPP) powder. Copper(II) oxide, basic copper(II) carbonate, and copper(I) oxide were effective catalysts for the decarboxylation. Both these catalysts with quinoline as solvent were necessary to cause the decarboxylation. The IR spectrum indicates that the PPP has a regular structure. The electrical conductivity of a pressed pellet was as high as 18 S/cm after vapor-phase doping with antimony pentafluoride.