Chiang Mai Journal of Science

Hydrogels from either 2-acrylamido-2-methylpropane sulfonic acid (AMPS-H+) or its sodium salt (AMPS-Na+) crosslinked with N,N’-methylene-bis-acrylamide (MBA) or ethylene glycol dimethacrylate (EGDM) have been prepared by redox-initiated free radical polymerisation to complete conversion. Different percentages of crosslinker and various concentrations of AMPS-H⁺ and AMPS-Na⁺ between 40-60% w/v were employed to obtain crosslinked hydrogels with different polymer contents and crosslink densities. The crosslinked polymers were swollen in water and the increasing water uptake followed as a function of time up to the equilibrium water content (EWC). It was found that the hydrogel sheets prepared from the highest monomer concentration (60% w/v) reached equilibrium at a slightly higher rate. In addition, the MBA crosslinker (≥1.0 mol %) had a significant effect on the water absorption profile and was found to be a more effective crosslinker than EGDM in terms of property modification. These results indicate that both type and concentration of monomer and crosslinker are highly influential on the degree of crosslinking which, in turn, affects the rate and capacity for water absorption of the resultant hydrogels. Thus, the balance between crosslink density and water absorption is of critical importance to their potential application as wound dressing materials.