Kinetics and Modeling of Free Radical Aqueous Phase Polymerization of Acrylamide with Acrylic Acid at Varying Degrees of Ionization
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Water soluble polymers find applications in both consumer (e.g. superabsorbers in diapers, antiscalants in laundry detergent, and thickeners in shampoo) and industrial applications (e.g. antiscalants, antiflocculants and viscosity modulators in water treatment and oil drilling). Despite their industrial importance, the understanding of their kinetics have lagged behind their organic counterparts due to interaction of the monomer and polymer with the solvent, affecting the kinetics, and complicating experimental analysis such as molecular mass measurements. Additionally, the high viscosity of these systems at low monomer concentration (~5 wt%) make it difficult to take samples during polymerization reactions. Improved and specialized experimental techniques allow for the study and better understanding of these complex systems. The work presented in this thesis focuses on the copolymerization of acrylic acid with acrylamide as a function of monomer concentration, monomer composition, temperature, and the degree of ionization of acrylic acid. Experimental monomer conversions and compositions were collected using an in-situ NMR technique developed and verified as part of this project. The in-situ NMR technique allowed for reliable data collection at monomer concentrations up to 40 wt%, covering a broader range of conditions than in previous literature, with reactivity ratios mapped over the complete range of monomer concentration and degree of ionization. Successful modeling of the acrylamide homopolymerization included the backbiting mechanism using rate coefficients measured by our collaborators on this project and allowed for a comprehensive model valid for a range of temperatures and monomer concentrations for our and literature conversion profiles. Models of the acrylic acid and acrylamide copolymerization at non- and fully ionized conditions were also developed. However, insufficient knowledge of rate coefficients highlighted some gaps in our understanding of this copolymerization.