Multiporous microstructure for enhancing the water absorption and swelling rate in poly(sodium acrylic acid) superabsorbent hydrogels based on a novel physical and chemical composite foaming system

In this article, we report a novel physical and chemical composite foaming system, which was used to successfully prepare high-performance and low-cost composite superabsorbent [poly(sodium acrylic acid) (PAA–Na)] hydrogels based on acrylic acid by free-radical polymerization in a water bath under a nitrogen atmosphere without the use of any organic solvents. The prepared hydrogels showed superabsorbent properties, high water-absorption abilities and swelling rates, a lighter packing density, and a multiporous microstructure. Fourier transform infrared spectroscopy and scanning electron microscopy revealed that the sodium dodecyl sulfate surfactant, sodium bicarbonate chemical foaming agent, and 1,1,2-trifluorotrichloroethane physical foaming agent were evenly distributed and grafted onto the PAA–Na matrix. Water-absorption, swelling rate, and packing density testing confirmed that the superabsorbent had a high water-absorption ability and swelling rate and a lighter packing density. Furthermore, we investigated the effects of different foaming agents, including chemical and physical foaming agents, on the swelling and water-retention capabilities of the superabsorbent hydrogels (SAHs).The results show that the combination of these foaming agents significantly improved the water-absorbing capacity. With the help of these foaming agents, we obtained PAA–Na hydrogels without any organic solvents for posttreatment or special porogens; this is an environmentally beneficial way to prepare SAHs for hygiene and biomedical products. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133 , 44149.