Surface states of PVA/chitosan blended hydrogels

Hydrogels were prepared from blends of poly(vinyl alcohol) (PVA) and chitos an in varying proportions. Electron spectroscopy analysis of the resulting hydrogel membranes, cast on glass plates, revealed that the chitosan compon ent was concentrated on the surface of the air-surface side of the membrane s and was nearly constant from 10 to 40 wt% of chitosan content of the blen ds. The increasing water-contact angle on the hydrogel surface with increas ing chitosan content indicated that the chitosan molecules were more hydrop hobic than were PVA molecules. The zeta-potential in the air-surface side o f the hydrogels increased to reach a constant value at more than 10 wt% chi tosan content at all experimental pH values (3.0, 5.0, and 7.2). Electron-p robe micro-analyzer results showed that the two-dimensional distribution of the chitosan component on the surface of the air-surface side of the Chito san-15 sample was heterogeneous when it was compared with that on the surfa ce of the air-surface side of the Chitosan-40 sample; the chitosan componen t on the surface of the Chitosan-15 sample was localized in islands. Observ ations of the Chitosan-15 sample by confocal laser-scan microscope gave the same results. (C) 2000 Elsevier Science Ltd. All rights reserved.