Enhanced swelling properties of a novel sodium alginate-based superabsorbent composites: NaAlg-g-poly(NaA-co-St)/APT

A novel alginate-based superabsorbent composite with enhanced swelling properties was synthesized by simultaneously grafted copolymerization partially neutralized acrylic acid (NaA), styrene (St) onto the sodium alginate (NaAlg) backbones in the presence of attapulgite (APT). The structure and morphology of the synthesized superabsorbent composites were characterized by Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible (UV-vis) spectra and Field emission scanning electron microscope (FESEM). Major factors affecting the swelling ratio according to Flory's theory were discussed. The superabsorbent composite synthesized under optimum reaction conditions exhibits the maximum swelling ratio of 587 g/g in distilled water and 73 g/g in 0.9 wt % NaCl solution. Compared with NaAlg-g-PNaA hydrogel, the simultaneous introduction of tiny amount of St and APT not only enhanced the swelling ratio but also increased the initial swelling rate. In addition, the effects of salt and pH medium on the swelling behaviors were investigated, and the results indicated that the composite showed smart swelling behavior in multivalent salt solution and better pH-responsitivity in the pH 2.2 and 7.4 solutions, which makes it promising for drug delivery application. (c) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012