Molecular weights and molecular dimensions of perfluoropolyether fluids

The weight‐average molecular weights of a series of fractions from two structurally different types of perfluoropolyether fluids were determined by low‐angle laser light scattering. The limiting viscosity numbers of both sets of fractions were measured in Freon TF® and related to molecular weights. By using established polymer solution theory, the coil dimensions of the molecules were calculated. Samples from both sets of fractions were subjected to analysis by gel permeation chromatography and the coil dimensions were derived by using the principle of universal calibration. Results from both methods agree well. Bulk viscosities and molecular weights were correlated.