A novel conjugated polymer with allene moieties in the polymer main chain, poly(4,4'-biphenylylene-1,3-diphenylpropadien-1,3-ylene), was synthesized from 1,3-bis(4-bromophenyl)-1,3-diphenylpropadiene by dehalogenative polycondensation using Ni(cod)(2). The polymer shows good solubility in common organic solvents, good processability for making thin films, intense blue fluorescence in solution and acid sensitivity resulting in coloration. The conductivity increased by an order of the 10(4) upon exposure to trifluoroacetic acid vapor.