Properties of iodine complexes of monosubstituted polyacetylenes

Iodine complexes of six monosubstituted polyacetylenes with methyl, ethyl, propyl, pentyl, t‐butyl, and phenyl substituents have been characterized by electronic spectroscopy. UV spectra allow the determination of the nature and the amount of active species, and photoelectronic spectra confirm the nature of these species. These measurements indicate the presence of iodine in the I and I2 forms. The concentration of I is low (0.12–4.0 mol%), and it depends on the nature of the substitutent, but this amount does not decrease when the films are left under vacuum. On the other hand, the adsorption of ε high concentration of iodine is possible; this adsorption is governed by a diffusion mechanism and is reversible. Iodine doping leads to a cis‐to‐trans isomerization of the polymers, except for poly(3‐3‐dimethyl‐1‐butyne), which can be isomerized to the cis or to the trans form, depending on the solvent employed. Electrical properties of polymer I complexes are also reported. Conductivities of about 10−4 Ω−1 cm−1 are obtained for all polymers in the presence of an excess of iodine.