MOLECULAR-DYNAMICS OF DISCOTIC CHARGE-TRANSFER COMPLEXES, DIELECTRIC-SPECTROSCOPY AND H-2 NMR-STUDIES

Using a combination of solid state H-2 NMR spectroscopy on selectively deuteriated samples and dielectric spectroscopy, the molecular dynami cs of discotic charge-transfer (CT complexes were investigated. These complexes show particular thermodynamic and flow properties. Considere d were mixtures of low molar mass donors and acceptors, low molar mass donors with main chain acceptor polymers and covalently linked donor- acceptor twins with different lengths of the spacer. A main result is that correlated rotational motions of discotic molecules or groups abo ut the columnar axis are observed in all systems except for the twin w ith the short spacer. This type of motion seems to be a general featur e of columnar phases. The non-discotic acceptor which is incorporated in the columns participates in this motion. The twin possessing a long spacer displays at high temperatures an additional process: it perfor ms a diffusion process between the columns. A further result is that b road biphasic regions exist in CT mixtures at the transition from the discotic to the isotropic state.