Cationic and anionic effects on the glass transition temperature for aqueous electrolyte solutions

Glass-forming composition regions of aqueous CH3COOM (M = Li, Na, K, Rb, Cs , and Tl), CF3COOM (M = Li, Na, K, Rb, and Cs), and E4NX (Et-4 = C2H5, X = OH, CH3COO, Cl, Br, NO3, and SCN) solutions are reported as a function of w ater concentration R (R = moles of water per moles of salt). Glass transiti on temperatures (T-g) were measured by a simple differential thermal analys is (DTA) method with a cooling rate of about 600 K-min(-1). The T-g of all solutions decrease with increasing R (decreasing salt concentration). It is found that T-g at the same R value decrease in the order Na+ > Li+ > K+ > Rb+ > Cs+ in all glass-forming composition regions of the alkali acetate sa lt and alkali trifluoroacetate salt solutions. T-g for Et4NX solutions decr ease in the order CH3COO- similar to OH- > Cl- > Br- > NO3- > SCN-. The eff ects of the cation and anion on the glass-forming behavior in these aqueous solutions are discussed.