M. Marzec1, J. Jankowski1, I. Sowa-Pawłowski1, W. Haase2,
S. Hiller2, M. Pfeiffer2, J. Oleszkiewicz1, S. Wróbel1
1 Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Kraków, Poland,
2 Institut fuer Physikalische Chemie, Th Darmstadt, Petersen Str. 20, D-64287 Darmstadt
Both electrooptical and dielectric properties of ferroelectric liquid crystals (FLCs) have been studied for
a double fluorinated compound (FFP) and for ZLI-3654 room temperature mixture. Both systems, designed by
E. Merck Company, are new materials for science and technology exhibiting very interesting dielectric
and electrooptic properties. Dielectric and electrooptic measurements were performed on oriented thin
films by using 10 mm EHC and 7.5 mm LINKAM cells.
The transition temperatures were found by polarizing microscopy and the textures were taken for uniformly
oriented samples by means of A.C. electric fields (V » 50 Vp-p and v
» 10 Hz).
By measuring the tilt angle it has been found that the cholesteric - SmC* transition for FFP compound
is of the first order and the SmA*-SmC* transition for ZLI-3654 mixture is of the second order
type according to Ehrenfest's classification. Spontaneous polarization has been measured by applying
a reversal current method. The results of dielectric and electrooptic investigations are described in
terms of the extended mean field theory. By using the dielectric and electrooptic parameters, the
rotational viscosity gf has been calculated and compared with the
Miesowicz viscosities. Possible applications of the systems studied are discussed.