UNPERTURBED DIMENSIONS OF SODIUM CARBOXYMETHYLAMYLOSE

Sodium carboxymethylamylose, degree of substitution (DS) = 0.55, has been prepared and fractionated according to molecular weight by gel permeation chromatography. Intrinsic viscosities, osmotic molecular weights, and second osmotic virial coefficients have been determined for the fractions and the bulk polymer in 0.5 Maqueous NaC1 at pH 8.0 and 35°. Polymer chain dimensions, unperturbed by volume exclusion, have been calculated from the experimental results using the method of Fox and Flory; the expansion factor was evaluated following recent suggestions of Berry. The experimental characteristic ratio Cx = 10, and this is approximately twice the value found for native amylose in neutral aqueous media. It is concluded that the conformation of sodium carboxymethylamylose in the present medium resembles that of aqueous unsubstituted amylose but that the proportion of helical units is smaller in the derivative owing to steric disruptions of the helical conformation precipitated by the substituent group. © 1969, American Chemical Society. All rights reserved.