A novel hydrogel based on sodium salt of acrylamide-2-methyl-1-propane sulfonic acid (AMPS-Na⁺) was obtained by free-radical copolymerization with acrylamide (AM), 1-vinyl-2-pyrolidone (VP) and acrylonitrile (AN) in the presence of N, N-methylenebisacrylamide (MBA) as a crosslinking agent. The hydrogel was characterized by IR, optical microscopy and scanning electron microscopy. The change in the composition of the hydrogel, pH of the swelling medium and ionic strength of the swelling medium were studied on the swelling kinetics. It was found to display swelling characteristics, which were highly dependent on these factors.

Hydrogels are well-known three-dimensional networks of polymer chain that absorb significant amount of water but do not dissolve in water and do not lose their structural integrity (Tokia and Tanaka, 1991). They find applications in controlled drug delivery systems (Serra et al., 2006; and Sutter et al., 2007), artificial implants (Kobayashi et al., 2003), soft contact lenses (Weissman, 2000), wound dressings (Siriwittayakorn et al., 2001), dialysis membrane (Paul and Sharma, 1995), and agrochemistry (Bajpai and Giri, 2003). Much attention has been concentrated on synthetic hydrogels for their applications as biomaterials (Chen et al., 2007), especially for their wound dressings, where the hydrogel assumes the skin's vital role of protecting the inner tissues, retaining body fluids, maintaining the water balance and regulating body heat (Young et al., 1998; and Nalampang et al., 2007). Hydrogels based on 2-hydroxyethylmethacrylate (HEMA) have been used for wound dressings (Prasitsilp et al., 2003). However, these materials still have some problems associated with their unsatisfactory skin adhesion and water absorption properties. Research for development of some alternative hydrogels for such biomedical applications is therefore important. 2-acrylamido-2-methylpropane sulfonic acid (AMPS-H⁺) or its sodium salt (AMPS-Na⁺) are strong ionic monomers and are easily dissolved in water. The polymer properties enhanced by AMPS-Na⁺ are: hydrophilicity, thermal stability, stability over broad pH range and ionic character (Liao et al., 2009). The advantages of these synthetic hydrogels are: they are soft and flexible (compared to HEMA) and any residual unreacted monomer can be removed more easily. These hydrogels have already attracted interest as a wound dressing material (Durmaz and Okay, 2000; Atta, 2002; and Liu et al., 2003) since it adheres to healthy skin but not to the wound surface and is easily replaceable without any damage to the healing wound. The water sorption properties as well as the mechanical strength of the hydrogel may be improved by introduction of a copolymeric system which has both hydrophilic and hydrophobic monomers. This generally results in a change in the maximum hydration degree and diffusion of the swelling agent into the gel as well as the reorganization of water molecules depending on the chemical composition and distribution of the hydrophobic monomeric units along the macromolecular chain (Bajpai et al., 2004).

Chemistry Journal, Water Binding, Hydrophobic Chains, Hydrophilic Chains, Optical Microscopy, Scanning Electron Microscopy, Drug Delivery Systems, Biomedical Applications, Hydrophobic Monomers, Macromolecular Chain, Hydrophobic Monomeric Units.