Preparation conditions and swelling equilibria of dextran hydrogels prepared by some crosslinking agents

Crosslinking reactions of Dextran (Dx) (M-n of 2.0 X 10(6) g mol(-1)) with some selective Cl-, P- and N-containing functional monomers such as epichlorohydrin (ECH), phosphorus oxychloride (POCl3) and N,N'-methylenebisacrylamide (MBAM) were carried out in the basic aqueous solutions (2.8 N NaOH) at 25-50 degreesC. The optimum conditions of the effective swelling and crosslinking for the each system studied were found in copper (CuCl2.2H(2)O) solution. The percent swelling, equilibrium swelling, initial rate of swelling, swelling rate of constant, equilibrium water content, and diffusion type and constant values were evaluated for Dx/crosslinker (CL) systems at 1 mg/100 ml copper (CuCl2.2H(2)O) solution. A substantial difference of these parameters observed for the various Dx/CL systems was explained by the effect of nature of crosslinking agents on the mechanism of crosslinking and swelling processes. It was shown that S-eq and M-c values increase depending on the nature of CLs in the following order: ECH > MBAM > POCl3. General scheme and proposed mechanism of crosslinking reactions in the Dx/CL systems were also described. (C) 2004 Elsevier Ltd. All rights reserved.