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 Et4NX (Et4 = C2H5, X = OH, CH3COO, Cl, Br, NO3, and SCN) solutions are reported as a function of water concentration R (R = moles of water per moles of salt). Glass transition temperatures (Tg) were measured by a simple differential thermal analysis (DTA) method with a cooling rate of about 600 K-min−1. The Tg of all solutions decrease with increasing R (decreasing salt concentration). It is found that Tg at the same R value decrease in the order Na+ > Li+ > K+ > Rb+ > Cs+ in all glass-forming composition regions of the alkali acetate salt and alkali trifluoroacetate salt solutions. Tg for Et4NX solutions decrease in the order CH3COO− ~OH− > Cl− > Br− > NO3− > SCN−. The effects of the cation and anion on the glass-forming behavior in these aqueous solutions are discussed.