A Study of Cryostructuring of Polymer Systems. 54. Hybrid Organo-Inorganic Poly(vinyl alcohol) Cryogels Filled with In situ Formed Silica

Macroporous viscoelastic poly(vinyl alcohol) (PVA) cryogels are formed via the cryogenic processing (freezing/incubation in the frozen state/defrosting) of concentrated solutions of the polymer. Such materials are of significant scientific and applied interest. This also concerns various complex and composite PVA cryogels containing soluble and insoluble (fillers) additives, respectively. Novel organo-inorganic hybrid PVA cryogels containing silica components have been obtained and studied in this work. These hybrid cryogels are formed via the interaction of sodium silicate with hydrochloric acid, which are introduced into an aqueous PVA solution immediately before its cryogenic processing. As a result, the transformation of the inorganic components occurs simultaneously with the cryotropic gelation of PVA. It has been found that the physicomechanical properties, heat endurance, and macroporous morphology of the obtained samples depend on the concentration of the inorganic additives and the temperature conditions of the cryogenic process. Moreover, it has been revealed that formed NaCl and additionally polarized hydrogen bonds between OH groups of PVA and silanol groups of in situ formed poly/oligo(silicic acids) have substantial effects on the characteristics of resulting hybrid cryogels.