Modeling of Poly Acrylic Acid and Its Salts

Xinhua Xu, Charles E. Carraher, Jr. and Mark D. Jackson Florida Atlantic University Department of Chemistry and Biochemistry Boca Raton, FL 33431 [Pg.165]

Poly(acrylic acid) is water soluble. Because of its water solubility and its ability to increase the viscosity of water, it is used as a thickener. It is also a good flocculent for sewage treatment and is added as a pigment dispersant in latex paints, and is used in binders and adhesives. Polymers and copolymers containing acrylic or/and methacrylic acid are manufactured at a rate of about 2,000,000 metric tons yearly. [Pg.165]

Neutralization of PAA leads to the formation of a polyelectrolyte. The Henderson-Hasselbalch equation can be used to relate the pH of a solution and the extent of neutralization. The Henderson-Hasselbalch equation is modified for polyelectrolytes [Pg.165]

Along with the electrostatic effect, a statistical or entropy effect is also present and accounts for the increased dependence of the equilibrium constant on the degree of neutralization, f, with decreased acid strength of the polyelectrolyte. Thus, cations from the base compete with protons from the acid for positions on the PAA chain. There are more possibilities or opportunities for a cation with respect to replacing a proton when f is below 0.5 (that is when neutralization is less than one half). The counter is true when f is above 0.5. Thus, PAA is a stronger acid compared with monoacids such as propenoic acid at low fractions of neutralization, whereas PAA is a weaker acid at high fractions of neutralizations. However, this entropy effect is overwhelmed for PAA by the electrostatic effect with the end result that PAA is a weaker acid than propenoic acid throughout its neutralization. [Pg.166]

In fact, concentrated solutions of sodium chloride are used to precipitate partially neutralized PAA (2). Further, if partially neutralized, even dilute solutions of PAA can be precipitated through addition of alkaline earth salts (3). [Pg.166]

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