Crosslinking of dextran with some selective Cl-, P- and N-containing functional substances in aqueous solutions

Abstract

Crosslinking reactions of Dextran (Dx) ( M n of 5.0×10 5 and 2.0×10 6 g mol −1) with some selective Cl-, P- and N-containing functional monomers such as epichlorohydrin (ECH), phosphorus oxychloride (POC1 3) and N, N′-methylenebisacrylamide (MBAM) as well as with 60Co-γ-irradiation were carried out in the basic aqueous solutions (2.8 N NaOH) at 25–50°C. The optimum conditions of the effective swelling and crosslinking for the each system studied were found. Some swelling parameters such as initial rate of swelling ( R S, %min −1), crosslink density ( ρ, g ml −1), equilibrium swelling ( S eq, %) and average molecular weight of crosslinked fragments ( M c, g mol −1) for the Dx/crosslinker (CL) systems studied were determined by using of kinetic methods and well known Flory-Rehner equation. A substantial difference of these parameters observed for the various Dx/CL systems was explained by the effect of nature and concentration of crosslinking agents on the mechanism of crosslinking and swelling processes. It was shown that R S and ρ values increase while the S eq and M c values decrease depending on the nature of CLs in the following raw: γ-ray-ECH-MBAM-POCl 3. Concentration of MBAM does not influence the initial rate of swelling while effect of CL concentration is strongly advented in the Dx/ECH and Dx/POC1 3 systems. Effectiveness of CLs is also confirmed by TGA analysis of crosslinking polymers. The formation of unsaturated crosslinked fragments, which are easily polymerized or photocyclodimerized as affected of u.v.-irradiation, was confirmed by Fourier transform infrared (FT-IR) spectroscopy. General scheme and proposed mechanism of crosslinking reactions in the Dx/CL systems was also described.