'Smart' glasses: Design, synthesis, characterization and applications of organically-modified silica sol-gels

Critical design criteria for development of smart or intelligent materials include physicochemical responses that can be modulated by external stimuli. As a part of this work, sot-gel chemistry was used to design novel materials that constitute the first generation of sol-gel—derived ‘smart’ materials. The overall focus of this research was threefold. First, synthesis of new ‘smart’ sol-gel materials. Second, characterization of these materials by various physical and chemical methods to determine structure, composition, and morphology as well as evaluation of their environmental sensitivity. Finally, applications of these materials based on their unique properties.; These glasses are characterized by an increased elasticity and porosity with a greater retention of water in their pores. Furthermore, it was established that these gels undergo swelling/shrinkage when subjected to different stimuli such as changes in temperature, pH, salt, solvent, and electrical potential. These dynamic responses mainly originate due to intake or expulsion of water as a result of its altered interactions with the gel when a stimulus is applied.; The unique properties of these gels were investigated to establish their practical utility for different applications. First, the property of stimuli-induced swelling/shrinkage of the gels was exploited in the form of prototype tweezers to convert volume changes into mechanical action (grabbing objects like human fingers). Second, the unique combination of hydrophobic, and hydrophilic groups in the network imparts these gels with selectivity for certain molecules that exhibit preferential noncovalent interactions. Based on its selectivity, these gels were used as matrices for separation, release and controlled delivery of molecules. Third, owing to the presence of amino groups in the network these gels were used for sequestering metal ions to form metal-oxo nanoparticles, and act as terminal electron donor for a photoreduction reaction. Finally, soft-lithography was used to construct micro-scale sol-gel architectures with lateral and vertical separation, and dimensional resolution.