Highly absorbing superabsorbent polymer

Acrylic acid (AA)–acrylamide (AM) based superabsorbent polymers (SAP) were synthesized by inverse suspension polymerization using potassium‐persulfate as the initiator, N,N′‐methylene bisacrylamide (BIS) as a crosslinker, sorbitan monostearate (Span 60) as the dispersant, cyclohexane as the solvent, and bis(methacryloylamino)‐azobenzene as the hydrophobic surface crosslinker. The influence of the polymerization parameters on the properties of the SAPs, water absorption (Q), morphology of the SAPs, swelling kinetics, salt resistance, and the reversibility of water absorption were investigated. The prepared SAPs have excellent water absorption, rapid water uptake, and good resistance to NaCl solutions. Furthermore, they show better reversible water uptake than the previously reported SAPs. The average water absorbency is 2800 g/g and 181 g/g of liquid absorbance in 0.025M NaCl solution. The initial water uptake rate is 1357 g/g/min and the reversibility of water absorption is 200 g/g in the repeated fourth cycle. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1357–1364, 2008