Modern Polymer Spect..

58 2 Segnientrrl Mobility of Liqriid Crystals aid LiCIuid-Ci.vJtulliiie Po1jwiei.s
PERIODICRL EUEHT ..............
................
TRIGGER PULSE .................
DRTR RCOUISITION .1([1[([(/(1/1/ i-
........-........ RESIILUTIoH z5us
..................
COHTRDL SIGHRL ..............m
ZOU,~, ioonz
, "------,
I. 0
1 ' 1 . 1 1 . 1 I
>
-_---- __- -____ -.-
Figure 2-25. Time scale of the
periodical event. control signal and
data collection sequence for the poling
experiment of the FLCP (2OHz at
0 10 28 I0 48 50 TIME/ns 42 "C, 100 Hz at 47°C).
~
- - ~
POLARITY: @ t 47OC
u
3 1 2
LL
0
!nn
I
n. 4
1.6
'3200 3flK 2800 2600 2400 2200 2000 1000 1600 1400 1200 1000 800 600
WAVENUMBER / =in '
Figure 2-26. FTIR-polarization spectra of the investigated FLCP prealigned at 47 "C and different
polarity of the electric field (radiation polarized at 45" to the rubbing direction according to the
geometry of Figure 2-74).
ism. Due to the perpendicular transition moment of the 1260 cm-' band relative to
the local chain axis it can be concluded that in the FLCP the mesogen and the
spacer are aligned preferentially parallel to each other but are perpendicular to the
backbone [16, 53, 831. The sinusoidal changes observed in the baseline of the spectra
are a consequence of the interference of the IR-radiation between the Ge-windows,
but do not disturb the evaluation of the absorption bands in the present case. A
stack-plot of time-resolved spectra recorded during several cycles of polarity
changes is shown in Figure 2-27. A good signal-to-noise-ratio is observed for all
spectral regions, except where the intensity exceeds an absorbance of 1.7.
Normalized absorbance/time-plots of the selected absorption bands are plotted
for experiments at different temperatures in Figure 2-28. As can be seen from this
figure, the reorientation at 47 'C takes only approximately 5 ms compared with