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

Systems of linear poly(ethylenimine), LPEI, with dissolved LiCF3SO3 and NaC F3SO3 have been studied using Raman and infrared spectroscopy. As the salt concentration is increased in the LPEI-LiCF3SO3 system, in turn "free" ions , contact ion pairs and the triple cation [Li2CF3SO3](+) each become the do minant species present, whereas contact ion pairs appear to be the dominant ionic species over the same composition range in the LPEI-NaCF3SO3 system. One of the major effects of adding salts to LPEI is the breaking of hydrog en bonds in the host polymer. As the salt concentration is increased in bot h systems, a somewhat abrupt onset of band broadening and widespread loss o f band structure is observed. (C) 2001 Elsevier Science Ltd. AH rights rese rved.