Porous superabsorbent hydrogel composites: Synthesis, morphology and swelling rate

Novel porous hydrogel composites with very high swelling capacity and enhanced rate of water absorption were synthesized in aqueous media at room temperature under normal atmospheric conditions. The porosity was induced through either foaming conducted in the course of polymerization or non-solvent dewatering of the as-synthesized gels. Kaolin was incorporated as an inorganic component in the polymerization process. The foaming technique was used to form porosity using three systems of different porogens (porosity generators), i.e. sodium bicarbonate, acetone and their combination. The as-synthesized gets were dried through oven drying and non-solvent dewatering. Morphology and swelling rate of the superabsorbent hydrogel composites (SHCs) were studied versus either the porogen system or the drying method. It was found that the simultaneous polymerization-foaming technique had great influence on the improvement of porosity, morphology of the porous structure and the rate of water absorption. It was also shown that the drying procedure had remarkable influence on preserving the preformed porosity. Methanol as a dewatering solvent produced SHCs with higher porosity and swelling rate in comparison with the. porosity of the hydrogels dewatered in acetone. Our invented methodology including simultaneous polymerization and foam formation using dual-porogen system and the subsequent methanol -dewatering approach was found to be the most efficient, highly practical, and costeffective route for preparing improved superabsorbing hydrogel materials.