Potentiometric titration of polyelectrolytes having stiff backbones

TLDR: In this paper, the potentiometric titration curves of carboxymethylcellulose and poly(D-glutamic acid) in the helical region are compared with the theoretical curves calculated assuming that the polyions are rods and have smeared charges on their surfaces.

Abstract: The potentiometric titration curves of carboxymethylcellulose, which has a relatively stiff backbone, and also of poly(D-glutamic acid) in the helical region are compared with the theoretical curves calculated assuming that the polyions are rods and have smeared charges on their surfaces. For carboxymethylcellulose good agreement is observed when its charge density is high, whereas as the charge density decreases the calculated curves deviate from the observed ones. The main reason for the disagreement at low charge densities may be attributed to the flexibility of the polymer backbone. For helical poly(D-glutamic acid) satisfactory agreement between calculated and observed curves is found if a radius thicker than the realistic radius is employed. The reason for the excessively large radius may be attributed to the inapplicability of the smeared charge model.