Conjugated polymers with main chain chirality .3. Synthesis of optically active poly(aryleneethynylene)s

Binaphthyl-based chiral poly(aryleneethynylene)s of different molecular weights have been synthesized. An optically active poly(aryleneethynylene), (R)-9c, is obtained by coupling an optically active binaphthyl molecule, (R)-2,2'-bis(octadecyloxy)-6,6'-diethynyl-1,1'-binaphthyl, (R)-8, with 1,4-diiodobenzene in the presence of tetrakis(triphenylphosphine)palladium(0) and cuprous iodide catalysts. GPC analysis of (R)-9c shows M(w) = 29 000 and M(n) = 12 000 (PDI = 2.4). Its specific optical rotation is [alpha](D) = -272.2 degrees (c = 0.5, CH2Cl2). Coupling of (R)-8 with 4,4'-diiodobiphenyl using tetrakis(triphenylphosphine)palladium(0) and cuprous iodide catalysts also generates an optically active poly(aryleneethynylene), (R)-10c. GPC analysis of (R)-10c shows M(w) = 37 000 and M(n) = 18 000 (PDI = 2.1). The specific optical rotation of (R)-10c is [alpha](D) = -281.70 (c = 0.18, CH2Cl2). A laser light scattering study of these polymers shows that the actual molecular weights (M(w)) of these materials are higher (1.4-2.5 times) than those obtained from GPC analysis vs polystyrene standards. The repeat units of these polymers have been synthesized. UV spectroscopic studies of the repeat units and of the polymers demonstrate that the conjugation of the polymers is determined by the conjugation in their repeat units.