Dielectric Relaxation in Liquid Polypropylene Oxides

Abstract

The dielectric properties of undiluted liquid atactic polypropyleneoxide have been studied as functions of temperature and molecular weight. The principal dispersion occurs at essentially the same frequency for all molecular weights at a given temperature, but at ower frequencies there is a small secondary loss peak that depends strongly on molecular weight. This secondary dispersion is shown to result from relaxation of a ``cumulative'' dipole, about 0.18 D per monomer unit, whose resultant magnitude depends on the long‐range conformation of the chain molecule. Experimental relaxation times for the secondary dispersion agree well with predictions based on Rouse—Bueche—Zimm theory. The main dispersion shifts with temperature according to the WLF equation.