Potentiometric titration of carboxyalkylated poly vinyl alcohol with mono-, di-, and trichloroacetic acids with alkali metal hydroxides and quaternary ammonium bases

ABSTRACT

Potentiometric titrations of the products obtained by polyvinyl alcohol first carboxyalkylated with chloroacetic acids were conducted with LiOH, NaOH, KOH, NH4OH, N[CH3]4OH and N[C2H5]4OH in deionized water, and with mixtures of LiOH and tetraethylammonium hydroxide of varying proportions. The results were expressed in terms of the modified Henderson-Hasselbach equation pH = pKa-n log [[1-alpha]/alpha]. Appreciable shifts in the titration curves to lower pH values were observed, accompanied by increase of the calculated capacity of the polyelectrolyte, in the sequence N[C2H5]4OH < N[CH3]4OH < NH4OH < KOH < LiOH. The values of pKa [at alpha = 0.5] where alpha is the degree of neutralization and is found to increase with the size of counterion. The titration curves obtained with mixture of LiOH and N[C2H5]4OH showed that the calculated values of capacity and the position of the curves were intermediate between those obtained with solutions of the single cations