THE THERMALLY STIMULATED CURRENTS SPECTRUM OF SIDE-CHAIN LIQUID-CRYSTALLINE POLYMERS - A FURTHER CONTRIBUTION FOR THE ATTRIBUTION OF THE DIFFERENT DISCHARGES AT THE MOLECULAR-LEVEL

The dipolar relaxation mechanisms in two side-chain liquid crystalline polyacrylates with very similar chemical structures have been studied by Thermally Stimulated Discharge Currents (t.s.d.c.). The only struc tural difference between the two polymers is in the terminal group of the mesogenic moiety: a cyano group for one polymer and a methoxy grou p for the other. This structural difference gives rise to differences in the t.s.d.c. thermogram of the two polymers which have been interpr eted in terms of the attribution of the observed discharges to molecul ar motions in the liquid crystalline phase. It was also shown that the distribution of the energies of activation and of the relaxation time s of the glass transition relaxation is influenced by the motions in t he liquid crystalline phase. Finally, it was observed that the shorten ess of the spacer which links the main-chain to the mesogenic moiety h as an influence on the t.s.d.c. signature of the studied polymers.