Electric conductivity of siliconorganic polyhomoconjugated polymer films upon adsorption of volatile organic compounds

The electrophysical parameters of polyhomoconjugated organosilicon polymer films are studied, and variation of their conductivity under the action of water, toluene, and ammonia vapors is measured. Films 1–2 $\mu$m thick are prepared by the casting method from a solution of poly[2,2-dimethyl-2-sila-1,3-propylene-(4, 4'-biphenylene)]a (polymer I) and poly[2-$n$-butyl-2-phenyl-2-sila-1,3-propylene-(4, 4'-biphenylene)]a (polymer II). In the course of conductivity measurement, organic volatiles and water are adsorbed due to a stepwise rise in the pressure over the sample from 10$^{-3}$ to 10$^{-1}$ Torr. The initial values of the resistivity of polymers I and II are estimated as 4 $\times$10$^9$ $\Omega$ cm. Exposure of the films to organic volatile vapors and water vapor causes a reversible change in the conductivity of the films. For polymer-I films, the conductivity upon adsorption of ammonia, toluene, and water vapors exceeds the initial value by 150, 10, and 600 times, respectively. The sensitivity of polymer-II films is lower by a factor of 1.5–2.0. The time of conductivity variation as the vapors are injected and evacuated is within 10 and 30 s, respectively. The mechanisms of organic volatile and water adsorption on the surface of polyhomoconjugated organosilicon polymer films are compared with adsorption mechanisms on the surface of $\pi$-polyconjugated organic films.