SYNTHESIS AND CHARACTERIZATION OF POLYACETYLENE AND SELECTED DERIVATIVES (ORGANIC METALS, SYNTHETIC CARBON-HYDROGEN)

The present study was carried out for the purpose of: (1) investigating the morphology of undoped and p-doped polyacetylene; (2) partially replacing the hydrogen atoms in (CH)(,x) with bromine to permit systematic modification of the properties of the polymer; (3) synthesizing partially oriented (CH)(,x) films by epitaxial polymerization of gaseous acetylene; and (4) synthesizing homogeneously doped (CH)(,x) film. The most significant results and conclusions are summarized below: (1) The morphology of (CH)(,x) films prepared by Shirakawa\u27s catalyst is fibrillar with an average fibril diameter of 200-400A. Doping of (CH)(,x) films with iodine and AsF(,5) induces a swelling of the (CH)(,x) fibrils to diameters ca. 500-1,000A. No evidence for a nonhomogeneous dopant distribution in doped (CH)(,x) was observed using conventional electron microscopy techniques. (2) Approximately 85% cis-(CH)(,x) films can be doped with bromine to give a metal of composition (CHBr(,y))(,x) (y = 0.02-0.46), which may then be partially dehydrobrominated at 150(DEGREES)C to yield new semiconducting polymers of composition (CH(,1-y)Br(,y))(,x) (y = 0.003-0.25). These polymers can be p-doped to yield a new series of organic metals. (3) Partially oriented (CH)(,x) film can be prepared by epitaxial polymerization of gaseous acetylene on crystalline (001) faces of biphenyl and terphenyl containing dissolved and/or adsorbed Shirakawa catalyst. Polarized visible-near IR absorption and reflectance studies demonstrate a change in optical absorbance and reflectance of ca. a factor of two for the partially oriented (CH)(,x) films. The films can be doped to metallic levels with AsF(,5). (4) Slow doping of trans-(CH)(,x) with AsF(,5) has been found to give material exhibiting significantly improved electronic and magnetic properties. Electrical and magnetic studies demonstrate a transitional electronic regime between truly semiconducting and truly metallic, exhibiting metallic-type conduction with essentially zero Pauli susceptibility