Physicochemical studies of oligodextran. II. Intrinsic viscosity‐molecular weight relationship

Abstract

Abstract The viscosity behavior of dextran in two good solvents and four mixtures of a good and a bad solvent was studied over the molecular weight range of 410 < M n < 32,000 at 25 and 50°C. In the molecular weight region larger than 2,000, the plot of log [η] versus log M n gave the usual linear relationship for all solvents used. The constants K and a of the equation [η] = KM a were determined and their dependence on the concentration of the nonsolvent in mixed solvents and on the temperature were discussed. Using the unperturbed dimensions of the dextran molecule estimated from the Stockmayer‐Fixman plots, the value of {〈L 〉/〈L 〉} 1/2 was calculated to be 1.7–1.8. The viscosity behavior for dextran with M n < 2,000 was qualitatively discussed as a deviation from the randomly coiled model.