RELAXATION AND CHARGE-TRANSPORT IN MIXTURES OF ZWITTERIONIC POLYMERS AND INORGANIC SALTS

Dielectric spectroscopy is employed to analyze the molecular dynamics and the charge transport in mixtures of zwitterionic polymers of the t ype poly(3-[N-(omega-methacryloyloxyalkyl)-N, N-dimethylammonio]propan esulfonate) with sodium iodide in the frequency range of 10(2) Hz-10(7 ) Hz and in the temperature range of 110 K-400 K. The amount of inorga nic salt added varies from 0-200 mol-% relative to the number of zwitt erionic groups present in the polymer, contributing strongly to the co nductivity. One relaxation process is observed whose relaxation rate d epends strongly on the length of the aliphatic spacer between the poly methacrylate main chain and the zwitterionic group. Exhibiting an Arrh enius-like temperature dependence with activation energy E(A) = 47 kJ/ mol, this relaxation process is assigned to fluctuation of the quatern ary ammonium groups in the side chains. At higher temperatures, the di electric properties and the conductivity are primarily dominated by th e mobile inorganic ions: conductivity strongly depends on the salt con centration, showing a pronounced electrode polarization effect. The fr equency and salt concentration dependences of the conductivity can be quantitatively described as hopping of charge carriers being subject t o spatially randomly varying energy barriers. For the low-frequency re gime and for the critical frequency marking the onset of the conductiv ity's dispersion, the Barton-Nakajima-Namikawa (BNN) relationship is f ulfilled.