A Raman spectroscopic investigation of methoxyl end capped PPO doped with NaCF 3SO 3

Abstract

Raman spectroscopy was used to study ionic association and polymer conformation in methoxyl end capped PPO (M–PPO) doped with NaCF 3SO 3, for temperatures ranging from 230–340 K. M–PPO of molecular weights 400 to 2000, pure and doped with sodium triflate of concentration O:M=15:1, were studied in order to investigate the importance of the end groups for ionic solvation. It is found that in M–PPO, in contrast to OH-terminated PPO, the number of dissociated ions is independent of molecular weight. Moreover, the ion-association in the M–PPO systems was found to be comparable to that reported for OH–PPO of molecular weight 4000 indicating that the latter is an excellent low molecular analogue to higher molecular weight systems. Furthermore, the absence of a distinct polarised metal–oxygen breathing mode in the M–PPO salt complexes indicates a polymer–ion interaction different from the symmetric configurations of chains wrapped around cations as suggested for PEO based polymer electrolytes. The solvation model of cations forming cross-links via coordinations to ether oxygens of adjacent chains is favoured.