A dielectric study on the relaxation and switching behaviour of liquid crystals confined within a colloidal network

M.C.W. Boxtel, van, M. Wübbenhorst, J. Turnhout, van, C.W.M. Bastiaansen, D.J. Broer

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Abstract

The mol. ordering and dynamics of a liq. crystal (LC E7) in the presence of a three-dimensional network of submicron particles have been studied by dielec. relaxation spectroscopy. The field-dependent orientation of the LC was quantified by the director order parameter and modelled by use of a three-phase model. The influence of the colloidal network on the mol. dynamics was assessed from the dielec. spectra, e.g. from the position of relaxation peaks as well as from the strength of the two principal relaxations (a and l). The spectra changed noticeably upon application of an increasing d.c. bias. A redn. of the threshold field was obsd. upon addn. of colloidal particles to the LC. This was assocd. with a switching between two metastable states induced by anchoring on the filler particles. Modelled spectra were found to be in good agreement with the exptl. data. The modeling showed that the confined LC phase is composed of two fractions, viz. an ordered and a disordered one with different mol. mobilities. Furthermore, switching expts. were conducted at various temps. in order to evaluate the impact of the colloidal network on the (temp.-dependent) orientational behavior of the LC mols. For the colloid-filled LC higher conductivities were found, which gave rise to longer switch-off times. [on SciFinder (R)]
Original languageEnglish
Pages (from-to)235-249
JournalLiquid Crystals
Volume30
Issue number2
DOIs
Publication statusPublished - 2003

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