HIGH FREQUENCY TITRATION OF POLYELECTROLYTES.

A modified high frequency titration instrument was used to characterize polyelectrolytes containing carboxylic substituents. Although high frequency titration has been widely used for the determination of end points in simple acid-base titrations, considerable difficulty was experienced when attempts were made to extend the technique to polyelectrolytes, mainly because of oscillator instability. This paper describes an improved oscillator circuit which may be of value to other investigators who may similarly wish to characterize aqueous solutions of polyelectrolytes. Typical high frequency titration data is shown for carboxyl containing polymers of acrylic acid, methacrylic acid, maleic acid and itaconic acid. A few comparisons are made with several carboxylic monomers, polyphosphates and polymers containing sulfonate groups. This technique is particularly useful for the determination of carboxyl equivalents and pK values of polymers and copolymers containing more than one type of ionizable substituent.