Structural relaxation and chain flexibility in polymeric ion conductors

Abstract The charge transport mechanism in ion conducting polymers is investigated. It is demonstrated that the flexibility of the host polymer is of major importance for the ionic mobility and also vital for an effective solvation of the dopant salt. Light (Raman and Brillouin) scattering has been used to determine the structural relaxation behaviour, polymer backbone flexibility and ion association phenomena. Results are given for PPONaCF 3 SO 3 complexes. The relaxation of the host polymer is shown to be non-exponential and the stretching increases as the polymer is complexed with the salt. Transient cross-linking of chains, which occurs via the dissociated ions and slows down the relaxation, is shown to be a major factor controlling the mobility of charge carriers. Ion-ion association, which reduces the number of charge carriers, increases with increasing temperature by contrast with the weak electrolyte behaviour suggested for polymer electrolytes. Another model based on free volume dissimilarity is introduced and experimental support from scaling observations in the molecular weight dependence is given.