Dielectric study of relaxation processes of polynorbornene derivatives

In order to explore the motion of the polar groups of side-chain liquid cry stal polymers with a rigid backbone two polynorbornene derivatives were stu died by means of dielectric spectroscopy. The complex dielectric permittivi ty was measured in a frequency range of 5 Hz-13 MHz and in a temperature ra nge of 20 degreesC-160 degreesC. The results are compared with the mechanic al spectra and the origin of four relaxations is discussed. It is postulate d that this is a complex system which one can treat as a system built up by the domains of nematic and smectic order. The motion of mesogen about its short molecular axis is characterised by the activation enthalpy of 85 kJ/m ol, in the case of nematic order, and 136 kJ/mol, in the case of smectic or der.