MICROSCOPIC HETEROGENEITY IN A BOWLIC COLUMNAR MESOPHASE AS PROBED WITH FLUORESCENCE DEPOLARIZATION MEASUREMENTS

The time-dependent fluorescence depolarization decays of the fluoresce nt probe 1,6-diphenyl-1,3,5-hexatriene (DPH) in the ordered and isotro pic phase of a columnar liquid crystal formed by bowl-shaped metacyclo phane cores symmetrically substituted by twelve alkanoyloxy chains hav e been recorded at various temperatures and analyzed using the global target approach. The measurements in the mesophase can be successfully analyzed only assuming a microscopic inhomogeneity of the columnar ph ase, with the probe partitioned between two environments, i.e. polar c ores and apolar aliphatic chains, showing very different ordering and dynamical characteristics. This behavior becomes evident only when all the fluorescence intensities, corresponding to different parallel and perpendicular orientations of the excitation and observation polarize rs, are analyzed simultaneously. The picture emerging from the analysi s supports other recent findings on this class of columnar systems.