Phase transition properties of poly(ethylene oxide) in aqueous solutions of sodium chloride

The phase transition properties of poly(ethylene oxide) (PEO), in aqueous solution, have been examined by differential scanning calorimetry (DSC) in the presence of NaCl (0-2 M). DSC studies show, for the first time, that the PEO phase transitions have an unusual line shape, the exact nature of which is dependent on NaCl concentration. The T-m (temperature of maximum apparent excess heat capacity) decreases with increasing [NaCl]. FT-IR experiments reveal that changes occur in the conformation of the C-O-C backbone of PEG, in the presence of 2 M NaCl, at the same temperature as the discontinuity in the apparent excess heat capacity function observed by DSC.