Effects of PVA, agar contents, and irradiation doses on properties of PVA/ws-chitosan/glycerol hydrogels made by γ-irradiation followed by freeze-thawing

Poly(vinyl alcohol) (PVA)/water soluble chitosan (ws-chitosan)/glycerol hydrogels were prepared by gamma-irradiation and gamma-irradiation followed by freeze-thawing, respectively. The effects of irradiation dose and the contents of PVA and agar on the swelling, rheological, and thermal properties of these hydrogels were investigated. The swelling capacity decreases while the mechanical strength increases with increasing PVA or agar content. Increasing the irradiation dose leads to an increase in chemical crosslinking density but a decrease in physical crosslinking density. Hydrogels made by irradiation followed by freeze-thawing own smaller swelling capacity but larger mechanical strength than those made by pure irradiation. The storage modulus of the former hydrogels decreases above 50 degrees C and above 70 degrees C it comes to the same value as that prepared by irradiation. The ordered association of PVA is influenced by both chemical and physical crosslinkings and by the presence of ws-chitosan and glycerol. These hydrogels are high sensitive to pH and ionic strength, indicating that they may be useful in stimuli-responsive drug release system. (C) 2008 Elsevier Ltd. All rights reserved.

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