THE EFFECT OF SIDE-GROUPS ON THE DIELECTRIC-RELAXATION OF POLY(METHYLHYDROGENSILOXANE)

The alpha-relaxation of a linear poly(methylhydrogensiloxane) has been investigated as a function of temperature and frequency using dielect ric relaxation spectroscopy. Replacement of the hydrogen with a hexyl group increased the temperature and broadness of the alpha-process, an d this is interpreted in terms of a slowing of the motions of the Si-O dipoles and plasticisation of the siloxane chain by the side groups. Replacement of the hydrogen with a mesogenic group produced a side-cha in liquid crystal which exhibited dielectric relaxation behaviour char acteristic of the glass and liquid crystalline states.