Dielectric relaxations in the liquid and glassy states of 47% polypropylene oxide in toluene as diluent

Abstract

AbstractMolecular relaxations in 47‐wt % polypropylene oxide of molecular weight 4000 in toluene as diluent have been studied by dielectric permittivity and loss measurements from 77 to 320 K, in the frequency range 1 Hz to 2 × 105 Hz. One relaxation process (β process) is observed in the glassy state below Tg (= 148 K), and two processes are observed in the supercooled liquid at T > Tg. Relative to the amplitude of the fast relaxation process (i.e., the local segmental motions of the polymer chain), the amplitude of the slow process is increased and that of the β process decreased on dilution of the pure polymer. The β process has an Arrhenius energy of 17 kJ mol−1. The rates of the two relaxations at T > Tg follow the Vogel–Fulcher–Tamman equation and seem to merge on cooling the liquid towards Tg. The relative temperatures at which the three relaxation processes occur at the rate of 1 kHz remain largely unaffected on dilution. The increase in static permittivity of the solution on cooling is more than anticipated from the temperature effects alone. It is suggested that the increase is due to the enhanced short‐range orientational correlation of the dipoles, which may involve H bonding.