Modern Polymer Spect..

Figure 2-51. Reversible dichroic behavior of
the v(C-N) absorption of the LSCE during an
elongation-recovery cycle to 45'%1 strain at
'7 'C.
C
H b
es~ = merogenlongsxls
e
Figure 2-52. Possible mesogen orientations
during the reorientation process at S=O (ul:
direction of internal stress induced during the
second crosslinking step. 0,: direction of external
stress applied during the rheo-optical
experimentj. (a I
Homeotropic orientation
perpendicular to the film plane: (b) isotropic
orientation; (c) planar biaxial orientation.
3.40 0. 80
3. 20
S
I
0. so
0.40 s
2.60
2.40
I I I I
10 LO 30 40
S'IKAIN IYuI
n. w)
0. 20
0. 10
Figure 2-53. Structural absorbance
and order parameter/strainplots
for the v(C3N) absorption
corresponding to the elongation of
the LSCE to 45% strain at 27°C.
of the v(CsN) absorption has been plotted alongside the order parameter for the
LSCE elongation step in Figure 2-53. The reference direction for the evaluation of
the structural absorbance has been chosen in accordance with the assumption made
for the order parameter (see Figure 2-50). As can be seen from Figure 2-53 the
structural absorbance decreases linearly up to about 25% strain. This is in agreement
with the reference polymer and can be attributed to the decrease in sample
thickness. Between 25'%, and 35% strain. however, the structural absorbance shows
an abrupt increase followed by only a slight decrease up to maximum elongational