Temperature and molecular weight dependence of the melt viscosity of polyethylene oxide in bulk

Isothermal viscosities η (at low shear rates) of polyethylene oxide fractions and blends were measured in the range from the monomer (glycol) to a molecular weight of about 10 5 and at a number of temperatures between 9 and 155°C. The fashion in which η varied with temperature was independent of molecular weight, except in the region of low molecular weight, and fitted very well a relation of the W ILLIAMS ‐L ANDEL ‐F ERRY type. Plots for log η vs. log M̄ v (M̄ v is the viscosity‐average molecular weight estimated from the limiting viscosity number in benzene at 20°C.) gave a smooth curve of sharp upward curvature, showing no asymptote of slope 3.4 in the region of high molecular weight nor a definite break. The curve has a slope as high as about 5 at the highest molecular weight studied. Thus the present system does not obey the well‐known empirical viscosity law of F OX and L OSHAEK . P ORTER and J OHNSON had previously reported a similar anomaly of the molecular weight dependence of η of polyethylene oxide, although their data were limited to a narrower range of molecular weight than ours. In the region where comparison can be made, the two data agree quite satisfactorily with each other.