Kinetic effects in the ionic association of poly(ethylene oxide) lithium triflate complexes

Ionic association in the high molecular weight poly(ethylene oxide)-lithium triflate (PEO)(n-) LiCF3SO3 complexes (n = 120 to n = 3), has been studied using infrared spectroscopy. With increase in salt concentration, the intensity of the peaks due to the crystalline compound (PEO)(3)LiCF3SO3 increases relative to the intensity of peaks due to ion pairs and "free" ions. However, the ionic association in complexes with n = 40 and 60 shows an interesting kinetic behavior in that the relative concentration of the compound grows at the expense of ion pairs and "free" ions with increasing:time. The rate of growth of the compound is much faster in the 40:1 complex than in the 60:1 complex. Temperature variation infrared studies of the 40:1 and 60:1 complexes indicate that there is a dramatic change in ionic association at similar to 60 degrees C, a temperature which can be identified with the melting of the crystalline PEO fraction. A mechanism has been proposed to describe the observed kinetic behavior. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.