Modern Polymer Spect..

a
-@
COWER
SRHPLE
._
2.5 Elec tric Fielrl-hiclirc.td Orieri tci tiori 43
CORXIRL HERIIHG UIRE
INPRRRED BERM
STEEL CORE UITH SRMPLE COHPRRTMENI
CELL /
TEFLOH IHSULRTION
'i
GERMANIUM
I ,
INFRARED BEAM
b -. , ,,__ TEFLON JACKET
Figure 2-8. Variable-temperature cell utilized for the spectroscopic characterization of the electric
field-induced alignment of liquid crystals. (a) Complete assembly of the accessory. (b) Expanded
ciew of the sample cell.
procedure, 1000 spectra with a time resolution of 0.05 ms were processed. A further
improvement of the signal-to-noise-ratio was obtained by averaging 10 spectra
recorded in 0.5-nis intervals, starting with the time corresponding to the onset of
applying the electric field. Thus, finally 100 spectra with a time resolution of 0.5 ms
were obtained. The data collection for the whole experiment required approximately
50 minutes.
Due to the increase of viscosity in the polymeric NLCP system, the reorientation
times varied between minutes and seconds, depending on the experimental temperature.
Thus, the conventional rapid-scan technique (Figure 2-2a) was applied to
follow the orientation and relaxation dynamics of the NLCP. In order to synchronize
the application of the electric field with the data collection. a common switch
was used to control the voltage [53].