Radiation-induced polymerization by free ions. Part 2.—Electrical conductivity measurements

Abstract

The radiation-induced specific electrical conductivities σ of rigorously dried cyclohexane, styrene, α-methylstyrene, and isobutyl vinyl ether have been measured as a function of dose rate I. A dependence of σ∝Iⁿ is observed with n between 0.50 and 0.59, depending upon the system. It is confirmed that the absolute measurements of σ for cyclohexane are consistent with G(free ions)≃ 0.1, on the basis of reasonable values for the ionic mobilities. The mean lifetime τ(sec) of the ions in the stationary state is obtained directly from σ(ohm^–1 cm^–1) by means of the relation 1/τ= 3.6 × 10¹²πσ/ε, where ε is the dielectric constant; τ is about 50 msec at I= 10¹⁵ eV cm^–3 sec^–1 for the monomer systems. At the same dose rate, the σ values for styrene and α-methylstyrene are lower than for cyclohexane by a factor of about 2. These results suggest that some charge carriers in the monomers have mobilities comparable to those in cyclohexane. The radiation-induced conductivities of the hydrocarbon monomers are not appreciably affected by the addition of ethanol and ammonia, but are reduced by water. Some possible reasons for this behaviour are examined.