Water Uptake and Urea Release of Hydrogels Based on Acrylamide, Methyl Methacrylate and N,N’–Methylene–bis–Acrylamide

Abstract

Water swelling kinetics, equilibrium water content, urea release kinetics, and freezable and non–freezable water of hydrogels based on acrylamide (AM), methyl methacrylate (MMA) and N,N’–methylene–bis– acrylamide (NMBA) were studied. A series of copolymeric gels of AM, MMA and NMBA as a crosslinker agent were prepared by free radical solution copolymerization using a mixture of ethanol and water as a solvent and benzoyl peroxide (BPO) as initiator. Equilibrium water content (Wω) was strongly influenced by copolymer composition. For hydrogels richer in AM, EWC increased as crosslinking decreased. Instead, for high content methacrylate hydrogels, the hydrophilicity of NMBA decreased Wω. Swelling process in distilled water was studied by dynamic swelling measurements (gravimetric method ). It was found that synthesized hydrogels fits second–order swelling. Urea release studies were carried out in distilled water and the urea concentration was determined by High Performance Liquid Chroma togra phy (HPLC). The hydrogels del ivered urea very ra pidl y, for all the studied compositions most of the urea was released in less than 200 minutes. Differential Scanning Calorimetry (DCS) was employed to determine the relative proportions of non–freezing and freezing water. DSC traces shown multiple endotherms that were related with different states of association between water and the polymeric matrix.