Inorganic Hybrid Gels Research Articles

Preparation and properties of organic–inorganic hybrid gel films based on polyvinylpolysilsesquioxane synthesized from trimethoxy(vinyl)silane

AbstractPolyvinylpolysilsesquioxane (PVPS) organic–inorganic hybrid gel films comprising polyethylene and siloxane backbone linkages were prepared through two routes: trimethoxy(vinyl)silane (VTS) was first subjected to radical polymerization of the vinyl groups, followed by acid‐catalyzed hydrolytic polycondensation of the trimethoxysilyl groups (route A) to afford PVPS; in the second route PVPS was prepared in reverse order (route B). PVPS gel films were transparent and homogeneous. We find that the mechanical and heat‐resisting properties correlate both to the degree of polymerization and the degree of cross‐linking. Copyright © 2003 John Wiley & Sons, Ltd.

Electrorheological fluids based on glycerol-activated titania gel particles and silicone oil with high yield strength

This article describes an electrorheological (ER) fluid based on glycerol-activated titania organic–inorganic hybrid gel particles and silicone oil with high yield strength. Based on a physical picture of a water-activated ER system, glycerol that has a high dielectric constant and boiling point is in situ prepared in the amorphous titania gel during the sol–gel processing. A small amount of ionic surfactant hexadecyltrimethylammonium bromide (CTAB) is employed to enhance charge carriers in particles. FTIR and XRD techniques are used to determine the nature and structure of the hybrid gel. Rheology test results show that a large static yield stress greater than 12.6 kPa is obtained when 3 kV/mm dc electric field is applied. This value is close to the value predicted by H. Conrad (MRS Bull. 8 (1998) 35) in theory. Furthermore, dynamic shear stress as a function of shear rate and temperature is also investigated. This ER fluid exhibits strong temperature dependence and a wide working temperature range from 0 to 120 °C, while its leaking current density is still low. More interesting is that the glycerol content is demonstrated to have an influence on ER effect and temperature dependence. Measurement of the dielectric properties of ER fluids shows enhancement of the dielectric constant and dielectric loss due to addition of glycerol and a regular dependence of them on temperature, which well explains the strong ER effect.

Interpenetrating Inorganic–Organic Hybrid Gels: Preparation of Hybrid and Replica Gels

Abstract An organic–inorganic hybrid gel was prepared by gelation of organic monomer or polymer solution in pores of a silica matrix. Furthermore, a replica organic gel was obtained from the organic–inorganic hybrid gel by treating the hybrid with aqueous hydrofluoric acid solution. The silica matrix of the hybrid gel was similarly dissolved using aqueous hydrofluoric acid solution, leaving the organic gel matrix.