Voltammetric characterization of soluble polyacetylene derivatives obtained from the ring-opening metathesis polymerization (ROMP) of substituted cyclooctatetraenes

Abstract

Abstract : High molecular weight, amorphous, partially substituted polyacetylenes (poly-RCOT) have been prepared using the ring-opening metathesis polymerization of substituted cyclooctetraenes. Spin-cast films of these polymers yielded unusually sharp, well-defined reversible electrochemistry for oxidative and reductive doping processes. As the substituent on the polymer chain was varied (R = alkyl, tert-butoxy, trimethylsilyl, and p-X-phenyl), the potentials for oxidative and reductive doping 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. Coulometry suggested that the reversible doping step represented a transfer of 1 electron for every 13-15 double bonds of the polymer. In contrast, the electrochemistry of predominantly- cis poly-RCOT films was irreversible, and indicated the presence of an electrochemical cis-trans isomerization on the first voltammetric sweep through either reductive or oxidative doping. Spectroelectrochemical studies indicated that the electrochemically doped poly- RCOT materials R=sec-butyl, (CH3)3Si) possessed mid-gap transitions at energies of 0.8-0.9 eV. The redox chemistry of the soluble, poly-RCOT (R=sec-butyl, (CH3) 3Si) species in CH2Cl2 solution was also investigated. Voltammetric studies showed that both the reductive and oxidative doping processes were chemically irreversible, and indicated that the dissolved polymers were electroactive over a wide range of potentials.