Investigation of a novel freeze-thaw process for the production of drug delivery hydrogels.

Poly(vinyl alcohol) (PVA) is a water-soluble, biocompatible and biodegradable polymer, which has been widely applied in biomedical fields. In this paper, novel physically cross-linked hydrogels composed of PVA and comprising a blend of poly(vinyl alcohol) (PVA) with different concentrations of HCl, NaOH and NaCl are prepared by a freezing/thawing treatment of aqueous solutions. The structure and complexation of the electrolytes were studied by Fourier transform infrared (FTIR) spectroscopy. The mechanical properties were investigated using rheometery and the thermal transitions of the hydrogels were examined by modulated differential scanning calorimetry (MDSC). Freeze/thawed PVA gels containing NaOH showed overall enhanced swelling with increased mechanical strength over traditional gels prepared by chemical or irradiative crosslinking techniques. These novel physically cross-linked hydrogels show promise for a variety of biomedical and drug delivery applications.