| The polymerization of 3-undecylbithiophene has been studied in supercritical carbon dioxide at 313 K and 10.5 MPa. The resulting polymer was characterized by several methods, and the results show that the poly(3-undecylbithiophene) obtained was highly conjugated and demonstrated significant electrical conductivity. It was also comparable in its molecular weight, electrical conductivity, conjugation, and structure, to the polymer formed using nitrobenzene as the solvent.; The polymerization reaction was also performed in situ in porous, crosslinked polystyrene using supercritical carbon dioxide. The temperatures, pressures, and mixing conditions were adjusted to obtain maximum swelling of the host substrate, and to allow oxidant and monomer incorporation into the host polymer. As expected, the morphology and electrical conductivity of the blends were greatly influenced by experimental conditions, the highest conductivity being obtained in blends formed at low temperature and moderate pressure. All blends were stable in the environment for several months.; The blends were also doped with iodine under atmospheric conditions and in the presence of supercritical carbon dioxide. Supercritical carbon dioxide greatly enhanced the impregnation and diffusion of iodine, resulting in a conductivity change that was one order of magnitude greater than that in the polymer doped at atmospheric conditions. The effect of different temperatures and pressures on iodine impregnation, solubility, and effective partitioning between the carbon dioxide and blend was also investigated. The temperature and pressure were found to affect not only the amount of iodine impregnated into the blend, but also the uniformity of the blend, and the distribution of iodine between the carbon dioxide and polymer blend.; These studies show that supercritical carbon dioxide is an excellent medium for in situ polymerization and blend formation, as well as for doping of polymers. It may also be possible to control the electrical conductivity of polymer blends formed in carbon dioxide by changes in temperature and pressure. |
