Acrylamide‐sodium acrylate copolymers: A comparison between copolymerization and hydrolysis

Abstract

AbstractPolyacrylamide‐co‐sodium acrylate has been prepared via copolymerization of acrylamide and acrylic acid, or the hydrolysis of a pre‐formed nonionic polymer. Both macromolecules had a charge of 24 mol% with a molar mass of 25 million g/mol. While one might expect similar performance, the hydrolyzed materials were superior in rheology modification, while the copolymerized samples worked better as flocculants. This hydrolysis reaction is influenced by the dyad sequence and produced a relatively uniform charge distribution along the backbone. These partially hydrolyzed polyelectrolytes had approximately 40% higher solution viscosities compared to the copolymerized samples. The rheological properties were also more tolerant to temperature, electrolytes, and hardness. Such molecules would be expected to perform well as pushing fluids as used in enhanced oil recovery processes. In contrast, when tested on an inorganic sludge, with a high level of polar and soluble hydrophobic molecules, the copolymerized sample provided larger flocs, a clearer filtrate, and faster settling. The hydrolyzed macromolecules essentially functioned only as a coagulant generating pin flocs. Depending on the application, polymer structure can be tuned by the method of synthesis. To the authors' knowledge, this is the first report comparing the influence of synthesis method on polyacrylamide solution properties and application performance.