CORRELATED CHAIN DYNAMICS IN THE NEMATIC PHASE OF 4-CYANO-4'-HEXYLOXYBIPHENYL

We report in this paper measurements of the Zeeman and Quadrupolar spi n-lattice relaxation times at two different deuteron Larmor frequencie s for the nematic phase of the perdeuteriated nematogen 6OCB. A model of correlated internal motion is used to account for both the quadrupo lar splittings and the spectral densities of motion. The nematic mean field is constructed using the additive potential method, while the co nformational transitions among be allowed configurations are described by a master equation. For modelling the quadrupolar splittings, we us ed 729 conformations, although this seemed impossible when the spectra l densities were fitted by minimizing the sum of squares of per cent e rrors. The pentane effect has, therefore, been used to limit the size of the transition rate matrix in the master equation. We found that th e dynamic model for liquid crystals proposed by one of us (1991, Phys. Rev. A, 43, 4310) is essentially correct for 6OCB.