| Abstract: | Cloud-point curves have been determined for aqueous solutions of poly(ethylene oxide) (PEO) at several concentrations for a variety of inorganic salts (sulfates, carbonates, nitrates, and chlorides). From these, theta conditions have been determined. The resulting dependences of the critical temperature θ (mostly between 300 and 360°K) on the molar concentrations (or ionic strengths) of the salts in solution cannot wholly be summarized in sequences of ion effects. The major findings are that sulfates and carbonates are much more effective in reducing θ than the chlorides and nitrates at the same concentrations. The trends found depend on salt concentration, i.e., certain plots of the data cross over, but they broadly agree with those found for comparable systems by other workers. Exceptional are the chlorides of Group II and LiCl which show minima when θ is plotted against molar salt concentration. While interpretations based on solvent structure-breaking are not adequate, there are similarities in behavior with the structure-breaking attributes of the ions based on independent studies (infrared). The results are briefly discussed in terms of current postulates: a more detailed discussion will accompany further experimental studies on these systems. |
