Synthesis and characterization of silica-derived, silicate polymers: monovalent (rubidium) /divalent (strontium) system

Silicate polymers containing both monovalent (Rb ⁺) and divalent (Sr ²⁺) ions were synthesized using our new synthesis method. Addition of Sr ²⁺ ions to Rb ⁺ ions made silicates less hygroscopic, as addition of Ca ²⁺ ions to Na ⁺ ions makes Na glass more resistant to water. Water (vapor from atmosphere) works as a plasticizer for the silicate polymer down to the saturation limit. By contrast, an ionic liquid can work as a plasticizer for the silicate glass beyond the limit of water vapor. Plasticization mechanism by an ionic liquid is found to be cation exchange reaction between the silicates and the ionic liquid. Finally, reduction of T _g value is found to be larger when: (1) an IL has better compatibility with ionic groups; (2) the monovalent-ion content of the divalent/monovalent glass is higher; and (3) higher pressure is applied during compression molding. The reasonings of these behaviors are discussed.