RELATIONSHIPS BETWEEN THE SOL-TO-GEL AND GEL-TO-GLASS CONVERSIONS.

Multicomponent gels were prepared with a wide range of pH-water combinations so that the skeletal structure of the desiccated gels varied from being less highly to more highly polymerized. The apparent value of isothermal viscosity, determined by isothermal shrinkage experiments, increased with time, presumably owing to polymerization and structural relaxation of the skeletal framework. In this chapter we review the concepts of gel formation and present evidence of how gelation conditions affect gel structure and, ultimately, the kinetics of the thermal conversion of gels to glass.