Preparation, Characterization And Properties Of Functional PVA-based Complex Hydrogel

The physically cross-linked complex hydrogels of poly(vinyl alcohol) (PVA), a water-soluble and biocompatible polymer, and polysaccharides are derived from chemical or physical mixing way and subject to freezing/thawing subsequently. To mix PVA with polysaccharides in chemical or physical way, PVA is grafted onto starch chains or simply blended with carboxylic derivative of starch and sodium carboxyl methyl cellulose (CMC) respectively. The structure, properties and their relationship of the complex hydrogels are analyzed and discussed. The main results of this paper are summarized as follows:1. Starch-g-PVA physical hydrogel with a controlled PVA branch length was prepared by freezing/thawing first. The result of DSC and WAXD indicated that the starch-g-PVA physical hydrogel was formed based on the crystallization PVA branch as the junction points. PVA branch length can be well controlled by adding chain transfer agent during PVAc was grafting onto starch. The ability of starch-g-PVA to form gel relied on the molecular weight of PVA. It was found that the starch-g-PVA could not form hydrogel when the molecular weight of PVA branch was lower than 1.5×104.2. Starch-g-PVA/Hydroxyapatite complex hydrogel was prepared. SEM analysis showed that hydroxyapatite (HA) was well dispersed in the network of the complex hydrogel, attributed to the hydrogen bond was formed between HA and starch-g-PVA.3. Carboxylic derivative of starch (MAS) derived from starch and maleic anhydride was mixing with PVA in solution and formed physically cross-linked hydrogel by freezing/thawing too. Compared to the starch/PVA hydrogel prepared in the same way, the interaction between the components of MAS/PVA hydrogel was enhanced due to the introduction of carboxyl groups. As a result, the crystallinity of the gel decreased and the the reswell property of the gel was much improved. In addition, the higher the degree of substitution of MAS is, the gel would reswell better. 4. A series of CMC/PVA hydrogels that contained different ratio of CMC and PVA were peprared. The hydrogels behaved pH-responsive. With the increase of the content of CMC, the crystallinity of the hydrogels would decrease. Consequently, the free volume of the network enlarged, the gel was much more easily to reswell and the hydrogel became more sensitive to the pH changes. A preliminary study of the CMC/PVA hydrogel as the carrier of the model drug, Hemoglobin (Hb), was performed. It was found that Hb keep active after subject to the freezing/thawing procedure and the release rate can be controlled by the content of the CMC.