A variety of poly(alkyl methacrylate-co-acrylic acid) (PS) copolymers were synthesized under conditions resembling those used in industrial processes. The interfacial tension dependence on the composition, the concentration of the polymers, and the presence of water-soluble quaternary ammonium salt (octadecyltrimethylammonium chloride) were investigated. The studies reveal that the presence of a quaternary ammonium salt decreases the interfacial tension to a high degree and improves the dispersing properties of the synthesized copolymers. Some examples of using PS copolymer with 15 mol % acrylic acid content as a dispersant in inverse suspension copolymerization process of acrylamide and acrylic acid are presented. (C) 2004 Wiley Periodicals, Inc.