totaitonal dynamics of nondipolar and dipolar solutes in an isotropic liquid crystal:Comparison with an isotropic liquid.

摘要

Rotational dynamics of a nondipolar solute,2,5-dimethyl-1,4-dioxo-3,6-diphenylpyrrolo-[3,4-c]pyrrole(DMDPP) and a diolar solute,coumarin 6(C6) has been studied in the isotropic phase of a liquid crystal,4'-methoxybenzylidene-4-n-butylaniline (MBBA) to understand the influence of pseudonematic domains on the dynamics of dopant molecules.The reorientation times of both DMDPP and C6 follow the Stokes-Einstein-Debye hydrodynamic model isntead of the Landau-deGennes model,which isused to describe the rotational relaxation of neat isotropic liquid crystals.However,comparison of the data for both DMDPP and C6 in MBBA to that in an isotropic solvent,1-decanol reveals that the probesare rotating considerable slower in the liquid crystal.Theses results indicate that orderedlocal structures of the liquid crystal exert more friction on the rotating solute molecule compared to an isotropic liquid.