Polyurethane/poly(vinyl alcohol) hydrogels: Preparation, characterization and drug delivery

Polyurethane based hydrogels were successfully prepared by freezing-thawing method of polyurethane (PU)/poly(vinyl alcohol) (PVA) mixtures in aqueous solution. The new materials were characterized by ATR-FTIR and SEM, confirming that the PU/PVA blend hydrogels form a network structure through hydrogen bonds and hydrophobic interactions. According to SEM analysis, an increase in the surface pore numbers and size was observed with increasing the polyurethane amount into the hydrogels. The average diameter of the pores was estimated as being between 4.05 and 39.05 gm. The PU/PVA blend hydrogels showed a lower tensile strength than pure PVA hydrogel, due to the extent of hydrogen bonding occurrence during the freezing-thawing process which determines a variation of porosity. The highest value of water swelling (1675%) was obtained for the hydrogel blend containing 50% PU, whereas pure PVA showed much lower ability for water (640%). These results can be explained by a denser structure of PVA network formed by applying successive freezing-thawing cycles. Three steps of water swelling were evidenced for the PU/PVA blend hydrogels: a fast one, a slow one and an equilibrium phase. In vitro technique was used for release of neomycin sulphate into a biological media model. The present investigations of the new PU/PVA blend hydrogels indicate their possible application as matrices for drug delivery.