Preparation and swelling characteristics of a superabsorbent nanocomposite based on natural guar gum and cation‐modified vermiculite

Abstract

Abstract A series of novel superabsorbent nanocomposites were prepared by the solution radical polymerization of natural guar gum (GG), partially neutralized acrylic acid [sodium acrylate (NaA)], and cation‐exchanged vermiculite (M n + ‐VMT) with ammonium persulfate as the initiator in the presence of the crosslinking agent N,N ′‐methylene‐ bis ‐acrylamide. Fourier transform infrared analysis revealed that NaA was grafted onto the GG chains and that M n + ‐VMT participated in the polymerization. X‐ray diffraction results showed that the occurrence of the cation‐exchange process changed the interlayer gap of vermiculite (VMT) and that M n + ‐VMT was exfoliated during polymerization to form a nanocomposite. The exfoliated VMT led to better dispersion in the GG‐ g ‐poly(sodium acrylate) matrix, as shown by scanning electron microscopy and transmission electron microscopy analysis. M n + ‐VMT improved the water absorption of the nanocomposite more remarkably than raw VMT, and Al 3+ ‐VMT enhanced the water absorption to the highest degree. The nanocomposite exhibited intriguing overshooting swelling characteristics in a multivalent saline solution and acidic pH solution and showed switching pH‐responsive behaviors in buffer solutions between pH 2 and pH 7.2. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011