The stability of solutions of poly(acrylic acid) in dioxane-water mixtures has been examined as a function of temperature and three phase boundaries have been located when water contents are less than 10 (wt/vol)%. These collapse into one boundary at higher water contents up to 25 (wt/vol)%. The cloud points have the characteristics of a quasi-LCST, a UCST, and an LCST, in order of increasing temperature, and this behaviour is comparable to the behaviour of poly(acrylic acid)-dioxane solutions. Measurements of the heat of dilution showed that this changes from being endothermic in dioxane solutions to exothermic in aqueous systems at temperatures below the quasi-LCST. Laser Raman spectra indicate the presence of hydrogen bonding between water and the polymer in the mixed solvent, which may explain the improved solvating power when water is added to dioxane.
|Number of pages||6|
|Publication status||Published - 1991|