Evaluation of chitosan/PVA blended hydrogel membranes

Blended membranes of chitosan and poly(vinyl alcohol) (PVA) in various ratios were prepared and treated with formaldehyde. Electron spectroscopy for chemical analysis of the membrane showed that the -NH2 group in chitosan changed into -N=C group after membrane treatment with formaldehyde. From the spectral change of FTIR, the hydroxyl groups disappeared and an acetal ring and ether linkage were formed for the reaction between the hydroxyl groups of PVA and formaldehyde. The results of differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) showed that (1) the crystalline area in PVA decreased after treatment with formaldehyde, (2) chitosan and PVA are not very compatible in the chitosan/PVA blended hydrogel membrane and (3) the thermostability of the membranes is enhanced by formaldehyde as crosslink agent. The effect of chitosan content on the water content and water vapor transmission rates on the blended hydrogel membrane were determined. It was found that the water content and water vapor transmission rates on the blended hydrogel membrane increased with increasing chitosan content. In antibacterial assessment, it appears that the antibacterial activity of all chitosan/PVA blended hydrogel membranes is similar. The viable cell number of aurococcus on the various chitosan/PVA blended hydrogel membranes was about (2.5 +/- 0.5) x 10(7) cells/ml. The permeation of creatinine, 5-FU, uric acid and vitamin B-12 through the chitosan/PVA blended hydrogel membranes were conducted. The linear relationship between permeability of creatinine, 5-FU and vitamin B-12 molecules and chitosan content in the chitosan/PVA blended hydrogel membranes were found. As the electrostatic attraction between the uric acid and chitosan in the membrane, the permeation of uric acid through the chitosan/PVA blended hydrogel membranes is higher for the membranes with chitosan content higher than 80% in the blended hydrogel membranes. (C) 2004 Elsevier B.V. All rights reserved.