Swelling properties of superabsorbent poly(acrylic acid‐co‐acrylamide) with different crosslinkers

Poly(ethylene glycol) diacrylate (PEGDA) was synthesized and characterized with Fourier transform infrared. A superabsorbent based on poly(acrylic acid-co-acrylamide) (PAAM) was prepared by free-radical solution polymerization with various crosslinkers. The relationship between the absorbency of PAAM in distilled water and in 0.9% NaCl solutions and the swelling time was explored. The order of the equilibrium absorbency of PAAM with different crosslinkers in 0.9% NaCl solutions was glutaraldehyde (GDA) < PEGDA < N,N′-methylene bisacrylamide (NMBA) < divinylbenzene (DVB). Some swelling models were used to fit the swelling data. The second-order kinetic model was best for describing the water absorption of PAAM with water absorption rate constants in the order of DVB < PEGDA < NMBA < GDA. The repeated absorbencies of PAAM in 0.9% NaCl solutions were also investigated. The repeated absorbency of PAAM with PEGDA as the crosslinker was better that that of PAAM with other crosslinkers. The repeated absorbency of PAAM was rather poor when DVB was used as the crosslinker, although the maximum absorbency was obtained. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009