| Over the past decade, sol-gel science and technology has experienced unpredictable advances. It is well known that during both the aging and drying processes, sol-gels undergo syneresis (gel shrinkage). Although there is extensive literature on aging and drying, there is relatively little detailed knowledge of aging mechanisms and even less quantitative analysis of the effects of aging and drying on gel structure. For many applications, the ability to control the degree of pore shrinkage is essential. However, to control the final sol-gel properties, it is necessary to elucidate the physical changes that occur in the system with time. In an effort to understand the sol-gel network, the internal pore structures of various silica sol-gels have been systematically quantified as a function of age and drying conditions.; More specifically, we have elucidated the internal structure of acid- and base-catalyzed silica gels via supercritical drying and nitrogen adsorption techniques. As a means to slow syneresis, we have modified the internal pores using polymer additives. Finally, the new silica-polymer hybrid gels have been successfully applied as the sensing layers of optical sensors. This research has expanded our knowledge of the internal pore structure of silica sol-gels and has created the potential for detailed customization of fabricated nano-porous materials. |
