THE EFFECTS OF MEHQ ON THE POLYMERIZATION OF ACRYLIC-ACID IN THE PREPARATION OF SUPERABSORBENT GELS

The effect of the monomethyl ether of hydroquinone (MEHQ) on the polym erization of acrylic acid was studied. The rate of polymerization was quantified at various levels of MEHQ by use of an in situ NMR techniqu e. While oxygen functions as an inhibitor in acrylic acid polymerizati ons, MEHQ was shown to function as a retarder. The decrease in the rat e of polymerization allowed the calculation of an inhibition constant for this system. MEHQ was found to remain in the polymerizing mixture throughout the course of the reaction, significantly reducing the rate of polymerization, but not reducing the molecular weight of the polym er. The data are consistent with direct reaction of MEHQ with initiato r fragments, but not termination of growing chains. Superabsorbent pol yacrylic acid gels were prepared and the properties measured. (C) 1997 John Wiley & Sons, Inc.