A comparative vibrational spectroscopic study of lithium triflate and sodium triflate in linear poly(ethylenimine)

Systems of linear poly(ethylenimine), LPEI, with dissolved LiCF 3SO 3 and NaCF 3SO 3 have been studied using Raman and infrared spectroscopy. As the salt concentration is increased in the LPEI–LiCF 3SO 3 system, in turn “free” ions, contact ion pairs and the triple cation [Li 2CF 3SO 3] + each become the dominant species present, whereas contact ion pairs appear to be the dominant ionic species over the same composition range in the LPEI–NaCF 3SO 3 system. One of the major effects of adding salts to LPEI is the breaking of hydrogen bonds in the host polymer. As the salt concentration is increased in both systems, a somewhat abrupt onset of band broadening and widespread loss of band structure is observed.