THE MOLECULAR CHARACTERIZATION OF SODIUM CARBOXYMETHYLCELLULOSE

Light-scattering and viscosity studies were made on unfractionated sodium carboxymethylcellulose, having 1.15 carboxymethyl groups per glucose unit, in 0.5, 0.05, and 0.01 M NaCl. The molecular weight, which was constant in the ionic strength range studied, and the normal concentration dependence of the scattering showed that aggregation was absent. The molecule had a high degree of extension, greater than that of uncharged derivatives. The end-to-end distance and the intrinsic viscosity increased with decreasing ionic strength. Extrapolation of data to infinite ionic strength gave an intrinsic viscosity of 5.70 which value is close to those of similar non-electrolytic cellulose derivatives. Direct evaluation of the universal constant, phi, which occurs in the Flory-Fox intrinsic viscosity equation, indicated that this theory is not applicable to highly extended polymers. Examination of the second virial coefficient indicated that the electrostatic interactions in this polyelectrolyte system are not well accounted for by the Donnan term alone.