Rheology of a lyotropic mesophase through a stress-relaxation experiment

We report on the first rheological study of the structural relaxations in a nematic liquid crystalline phase. Linear dynamic and transient shear experiments were applied to a polydomain nematic phase of the CTAB/water system: a liquid crystalline mixture composed of 28 wt% CTAB at 35 degrees C. The decay of the shear modulus, G(t), was analyzed using the CONTIN inverse Laplace transform to obtain a distribution of relaxation times which were compared with ones from the usual fitting procedure based on a generalized Maxwell model. The behavior of the nematic lyotropic structure of the CTAB/water system is characterized by the presence of both slow and fast relaxation times. These were interpreted as being due to a progressive loss of the lyotropic domain orientation and to the breaking/reforming process of the cylindrical aggregates, respectively.