Crystalline phases of poly(ethylene oxide) oligomers and sodium triflate: Changes in coordination and conformation with chain length

Crystalline phases of monoglyme:NaCF3SO3, diglyme:NaCF3SO3, and tetraglyme:NaCF3SO3 have been characterized by DSC, X-ray diffraction, and vibrational spectroscopy. Comparison of the structures allows for the investigation of the effect of the number of ethylene oxide units on local structure in these systems. The cation environments, anion environments, and glyme conformations of the three compounds are compared with each other and to the high molecular weight crystalline poly(ethylene oxide):NaCF3SO3 compound. The cation coordination number varies from 5 to 7 and consists of varying contributions of ether and triflate oxygens. Higher coordination numbers are observed with increasing numbers of ethylene oxide units. Similar conformational sequences are observed in the structures. The comparison of the vibrational spectra of the compounds reveal differences in the v(s)(SO3) and delta(s)(CF3) modes related to the. different potential energy environments of the triflate anion in the compounds.