Intrinsic viscosities of cellulose derivatives

Abstract

Intrinsic viscosities of cellulose acetates of degrees of substitution 2.86 and 3.00 and of cellulose trinitrate have been investigated as functions of temperature, solvent, and molecular weight. Large negative temperature coefficients (ca. −0.6% per degree) of [η] appear to be characteristic of cellulosic chains. These observed decreases in [η] with temperature are due to increases in chain flexibility, which are reflected in decreases in the characteristic ratio r 02/M. The rather large variations in [η] with the solvent are shown also to be manifestations of altered chain flexibilities brought about in some manner, as yet unexplained, by specific solvent interaction. This behavior stands in marked contrast to that of other polymers for which r 02/M is independent of the solvent and varies only slightly with temperature, and for which solvent effects on [η] are wholly attributable to changes in the molecular expansion (α3) brought about by solvent action,

Reply:

“…Moreover, since both HPC and HPMC have rigid chains due to the chemical nature of cellulosic polymers (glucose unit), their solutions exhibit nonideal solution behavior as noted by Flory 14. Therefore, they have different water absorption characteristics 15–17…”

Single sample methods for estimating the parameters of the Mark-Houwink equation

“…It is assumed that the parameter K is independent of molecular weight. This may not be the case for stiff chain polymers (24,25) for which the draining effect is also important.…”

Viscosity and the prolate ellipsoid model applied to low molecular weight cellulose triacetate fractions

“…Dependence of the viscosity on solvent has been noted for cellulose derivatives at higher DP levels [34] but a more striking effect is the decrease of viscosity with temperature, a property of cellulose which is unique among polymers. Flory, et al [34] have shown that the effect of both solvent and temperature on the viscosity of cellulose derivatives is due to a decrease in stiffness, a reduction in the ratio R2/DP, because of alteration in the potential restricting rotation about the glycosidic bond. A freely rotating polymer, on the other hand, expands by long range excluded volume effects and by attractive forces of the solvent for the chain as a whole.…”