Blends of sodium alginate (SA) and lignosulphonic acid (LS) has been prepared in the ratio of 80/20. The prepared blends were crosslinked using chlorides of calcium, barium, strontium and aluminum. The crosslinking of blends was done for different time intervals and then these blends were subjected for swelling studies in aqueous medium of pH 7.4. The observations indicate that the crosslinking is diffusion controlled and is affected by the size of metal ion and the type of alginate used. The improved swelling time for crosslinked blends in aqueous medium supports the fact that the stability under physiological conditions of the blends is improved due to crosslinking with the metal ions. Calcium chloride and barium chloride forms strong crosslink with the blend. Calcium ion crosslinked blends can be considered suitable for biomedical drug applications. The investigations on crosslinked blends using FTIR, SEM, XRD and EDAX are in close agreement with swelling results.

Keywords: sodium alginate; lignosulphonic acid; swelling; crosslinking