H-2-NMR STUDY OF MOLECULAR ORDER AND DYNAMICS IN MIXTURES OF 80BCAB AND NTPCHB

H-2-NMR measurements have been performed on pure 8OBCAB-d2 and on its mixture with compounds of the nTPCHB series. The aim of this investiga tion was to achieve an insight into the unusual mixing properties of t hese compounds, which have been associated to the formation of molecul ar pairs in the smectic A phase. By quadrupolar splittings measurement s, performed at various temperatures, ordering information on the vari ous mixtures was obtained. The Zeeman (T(1Z)) and the quadrupolar (T(1 Q)) relaxation times were simultaneously measured by the Jeener-Broeka ert experiment; then the temperature dependence of the individual spec tral densities J(omega) and J(2omega) was analysed. The fitting of the se parameters has been obtained using Nordio's rotational diffusion mo del. Comparison of all the mixtures at the same reduced temperature (T /T(NI)) showed a connection between the presence of the nematic re-ent rant behaviour and the slowing down of both D(parallel-to) and D(perpe ndicular-to) elements of the rotational diffusion tensor.