Preparation and Characterization of Poly (lactic acid) -Poly (vinyl alcohol) Composite Hydrogels.

Poly (lactic acid) (OLA) composite hydrogels with poly(vinyl alcohol) (PVA) were obtained by the repeat-freeze thaw method. A mixture of PLA fine particle aqueous dispersion and PVA aqueous solution with high degree of the saponification was used. These hydrogels could be obtained even for very low contents of PVA: 1/20∼1/100 of PVA/PLA. The hydrogel can be prepared over the range from the rubber-like elasticity solid to the brittle solid by the change of the mixture proportion of PVA. A porous dried gel was obtained by drying the hydrogel at room temperature. The dried gel turned into the hydrogel by immersion in water. However, as the content rate of the PLA increases, dried gels would be able to absorb not only aqueous solution but also hydrophobic liquids such as a hydrocarbon. The SEM observation of the dried gel suggested that PVA covered the surface of PLA and cross-linked by physical bonds such as hydrogen bonds. [ABSTRACT FROM AUTHOR]