| Abstract
| - The structure of poly(vinyl alcohol) (PVA) hydrogels formed as a result of freeze/thaw treatments of aqueoussolutions of the polymer (11 wt % PVA) in the freshly prepared state is analyzed through the combined useof small (SANS) and ultrasmall (USANS) angle neutron scattering techniques. The structure of these hydrogelsmay be described in terms of polymer rich regions, with dimensions of the order of 1−2 μm, dispersed in awater rich phase, forming two bicontinuous phases. The PVA chains in the polymer rich phase form a networkwhere the cross-linking points are mainly crystalline aggregates of PVA having average dimensions of ∼45 Å.The structural organization of freeze/thaw PVA hydrogel membranes does not change either after rehydrationof dried gels or in the presence of a tensile force. Finally, addition of surfactant micelles inside the gelprovides a formulation with both hydrophobic and hydrophilic regions, which demonstrates the potential ofthe system for drug delivery. Both SANS and EPR measurements show that sodium decylsulfate (C10OS)micelles do not significantly interact with the PVA gel. Variation of the gel structure by the number offreeze/thaw cycles should modulate the rate of release of an active constituent, for example, in a dermalpatch.
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