Cryostructuring of Polymeric Systems. 71. Poly(vinyl alcohol) Cryogels Formed by Freezing–Defrosting of Concentrated Polymer Solutions in a Dimethyl Sulfoxide–Dimethylformamide Mixture

Noncovalent cryogels have been prepared via the cryotropic gelation of 100 g/L poly(vinyl alcohol) (PVA) solutions in dimethyl sulfoxide (DMSO) and its mixture with dimethylformamide (DMF) (75 : 25, vol/vol). The physicochemical characteristics of the cryogels have been determined for both freshly prepared (“primary”) samples and samples subjected to replacing organic dispersion media by water with the formation of hydrated (“secondary”) PVA cryogels. It has been shown that the elasticity moduli of the samples formed in the DMSO/DMF medium are significantly higher than those of the cryogels prepared in the DMSO medium. Moreover, the former gel matrices undergo a greater volumetric shrinkage during hydration in comparison with the latter cryogels. In addition, cryogels prepared in the DMSO/DMF medium are highly transparent. The kinetic study of releasing a model drug, ibuprofen sodium salt, from the “secondary” cryogels has shown the absence of significant diffusion hindrances for the release of this biologically active compound from the gel carriers.