Dielectric relaxation in amorphous polyepichlorhydrin and polyepibromhydrin

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Abstract
The variation of the dielectric permittivity and loss factor with frequency and temperature has been measured for two polyethers with polar side groups, polyepichlorhydrin and polyepibromhydrin. Both polymers showed two distinct relaxation processes. The high-temperature relaxations correlate with the glass-to-rubber transition temperatures in accord with the WLF equation. For the low-temperature relaxations, attributed to rotational motion of the side groups, the activation energy for the bulkier—CH2Br case is smaller than—CH2Cl. This effect and the extreme broadness of these relaxations are explained by considering dipole-dipole interactions. Calculations for selected model conformations show that intramolecular dipole-dipole interactions are weak, but that inter-molecular dipole-dipole interactions can account for the observed order of activation energies.