Acrylic acid and acrylamide were polymerized by a peroxydisulfate-suberic acid redox system under a nitrogen atmosphere both in the presence and in the absence of ultrasound (at constant frequency). The rate of polymerization was determined for different concentrations of monomer, initiator, and activator and for different percentages of ultrasonic intensity. The polymers were characterized by X-ray diffraction and H-1-NMR spectroscopy. A probable mechanism is proposed to explain the experimental results obtained. (C) 2003 Wiley Periodicals, Inc.