Chitosan films with 5 and 7% of chrysotile and 5% of montmorillonite have been investigated. It was found that the electrical conductivity of chitosan films is reduced by several orders of magnitude with adding filler. The temperature dependence of the conductivity was obtained and, as result, defined activation energy of conductivity, which increases from 0.2 eV (pure chitosan) to 0.31 eV (chitosan with chrysotile). It is shown that the conductivity of chitosan is ionic and the temperature dependence of the conductivity of chitosan films correctly described by the Rice-Roth model for solid electrolytes:
σ(T) = 2(Ze)2·nWτ·exp(-W/kT)/3kTM,
where W - activation energy, n - concentration of ion, τ - time life of ion in activated state, Ze and M - charge of ion and mass of ion respectively. It is determinated that the ion concentration is decreased when adding filler in polymer. This fact can be explained by the sorption of water molecules on filler particles. Thus, the presence of water in the polymer structure determines the ionic conductivity of the polymer. Main contribution to the conductivity of chitosan films make hydrogen ions. The addition of mineral sorbent water fillers reduces the number of free ions and can control the volume of the electric conductivity of this biopolymer.
