Silica gel is shown to be elastic in the presence of dry alcohol, but viscoelastic (VE) in aqueous media; the rate of VE relaxation increases with the concentration of water. At 25 vol% water in ethanol, the rate of viscoelastic relaxation decreases with pH, approaching zero (i.e., elastic behavior) at pH 1.5. Elastic behavior is also seen in methanol, but VE relaxation is rapid upon addition of 1% triethylamine. It is concluded that VE relaxation results from attack by the liquid on siloxane bonds in the gel network. The kinetics of relaxation are well described by the theory presented in Part I.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Condensed Matter Physics
- Materials Chemistry