Francis Ignatious

A d.c. conductivity study of tetra-alkyl ammonium inserted polyacetylenes

Abstract The maximum conductivities of cis and trans Shirakawa polyacetylene doped with three different tetra-alkyl ammonium doping agents are reported. Utilizing one system, the conductivity was investigated as a function of the cation size. A linear relationship between log σ and the size of the R 4 N + ions is deduced. The influence of THF on the measured conductivities was examined and compared to the effect of the solvation of the cations in the alkali-metal-doped PA. The study was extended to other solvents like DMF, DME, dioxane, cyclohexane, etc. The temperature dependence of the conductivity of films doped with various R 4 N + cations was determined and the activation energies were calculated. They were found to be much higher than those of the alkali-metal-doped PA having the same dopant concentration.

Chemical insertion of organic cations into polyacetylene: Kinetics and doping level control

Abstract The kinetics of the chemical insertion of tetraalkylammonium cations into Shirakawa polyacetylene films is entirely controlled by the interfibrillar diffusion of the dopant. The maximum doping level Y max achieved at the end of the reaction is limited not only by the redox potential of the reductor used, but also by the size of the inserted cation and the chemical stability of the doped sites. Homogeneously doped films can be prepared by chemical doping using thermodynamic control of the doping level, or by an ion-exchange technique.

Kinetics of intercalation of tetraalkylammonium ions into polyacetylene

Abstract The doping kinetics of Shirakawa polyacetylene (PA), involving bulky R 4 N + like Bu 4 N + , Hep 4 N + and Dodec 4 N + , was undertaken. From the drastic influence of dopant concentration and film thickness on the kinetics, the interfibrillar diffusion of the dopant was identified as the rate-limiting step. However, a minimum value of 10 −15 cm 2 s 2−1 was estimated for the intrafibrillar diffusion constant. The relaxation of the narrow electron spin resonance line, produced during a short heterogeneous doping of cis -PA, was critically examined in the case of each of the above cations. The relaxation times were found to decrease in the order Bu 4 N + 4 N + 4 N + .

Ammonium doping of polyacetylene by a chemical method

Abstract The different methods of chemically inserting organic cations in polyacetylene are discussed. The most efficient among them was exploited quantitatively to insert tetraalkyl ammonium ions (R4N+) of well defined size. The influence of the size of (R4N)+ ions on the maximum doping levels, room temperature conductivities and ESR band widths of the doped products was demonstrated.

Tetra-alkyl ammonium complexes of (CH)x and (CD)x. A comparative ESR investigation

Abstract The ESR spectral characteristics of (CH) x and (CD) x , doped to 6% and containing various alkali metals and R 4 N + ions, were investigated. The doping levels were thermodynamically controlled by carbanionic systems of suitable redox potentials. In both (CH) x and (CD) x , the linewidths were found to increase in the order Li + + + . Linewidths of R 4 N + complexs are all narrower than those of the alkali metal complexes, and they narrow on going from (CH) x to (CD) x . These differences in behaviour are discussed in terms of an important contribution of spin-orbit coupling in alkali-metal-doped polyacetylenes and of hyperfine interactions in R 4 N + -doped polyacetylene.