DIELECTRIC PROPERTIES OF AROMATIC POLYESTERS - RELAXATION BEHAVIOR OF POLY(DIETHYLENE-GLYCOL-TEREPHTHALATE)

In the reported experiments, the dielectric behavior of a low molecular weight fraction of poly(diethylene glycol terephthalate) has been studied over the frequency range 10**2 to 10**5 Hz for temperatures between minus 67 and plus 51 degree C. Two relaxations, alpha and beta , which exhibit pseudoactivation energies of 52 and 8 kcal/mole, respectively, have been found. The alpha relaxation, associated with the glass transition of the polymer, is amenable to a Williams-Landel-Ferry (WLF) analysis. The dipole moment ratio ( mu **2)/Nm**2 (where ( mu **2) is the mean square dipole moment of a chain consisting of N bonds and m**2 is the average of the squares of the bond moments) has also been calculated using the dielectric data obtained for the polymer in the undiluted state. The calculations yield ( mu **2)/Nm**2 equals 0. 710, a value in a very good agreement with that obtained from measurements in solution.