VOLTAMMETRIC CHARACTERIZATION OF SOLUBLE POLYACETYLENE DERIVATIVES OBTAINED FROM THE RING-OPENING METATHESIS POLYMERIZATION (ROMP) OF SUBSTITUTED CYCLOOCTATETRAENES

High molecular weight, amorphous, partially substituted polyacetylenes (poly-RCOT) have been prepared using the ring-opening metathesis poly merization of substituted cyclooctatetracnes. Spin-cast films of these polymers yielded unusually sharp, well-defined, reversible electroche mistry for oxidative and reductive doping processes. As the substituen t on the polymer chain was varied (R = alkyl, tert-butoxy, trimethylsi lyl, and p-X-phenyl), the potentials for oxidative and reductive dopin g changed by 0.3 V. In addition, the separation between the oxidative and reductive doping processes varied from 1.66 V to >2.0 V. Coulometr y suggested that the reversible doping step represented a transfer of 1 electron for every 13-15 double bonds of the polymer. In contrast, t he electrochemistry of predominantly-cis poly-RCOT films was irreversi ble, and indicated the presence of an electrochemical cis-trans isomer ization on the first voltammetric sweep through either reductive or ox idative doping. Spectroelectrochemical studies indicated that the elec trochemically doped poly-RCOT materials (R = sec-butyl, (CH3)3Si) poss essed mid-gap transitions at energies of 0.8-0.9 eV. The redox chemist ry of the soluble, poly-RCOT (R = sec-butyl, (CH3)3Si) species in CH2C l2 solution was also investigated. Voltammetric studies showed that bo th the reductive and oxidative doping processes were chemically irreve rsible, and indicated that the dissolved polymers were electroactive o ver a wide range of potentials.