Modern Polymer Spect..

. I
polymer chain
0 0
“I
chromophore with
a donor I acceptor System
(“sideon” - Ilnk)
k
cn,
/\
H,C
chiral mesogen
(“endon“ - Ilnk)
chromophore
3‘
..-. I
. .
’.
, polymer chain
’. . ... .. .
.. ’..
spacer
oriented
mesogen
Figure 2-41. Possible models of mesogen
and chromophore alignment in the sheared
FLC-copolymers. (a) The chromophore
orients parallel to the local polymer chain
axis and the shearing direction, whereas the
mesogen aligns perpendicular to the chromophore.
(b) The interaction between the
chromophores and the mesogens dominates
and induces a parallel alignment to each
other and a perpendicular orientation to the
shearing direction.
2.7.2 Orientation Mechanism of Liquid Single Crystal Elastomers
During Cyclic Deformation and Recovery
The application of the previously discussed techniques to induce monodomain
structures in side-chain liquid-crystalline polymers by the application of electric or
electromagnetic fields, by shearing or on anisotropic surfaces, frequently leads to
comparatively low, macroscopically uniform orientation. Additionally, the methods
are limited to a sample thickness of about 100 pm. Liquid-crystalline side-chain
elastomers do not have this restriction, because a high macroscopic orientation can
be induced in polymeric networks by mechanical deformation up to a sample
thickness of about a centimeter [103, 1091. The synthesis of such systems can be
performed by crosslinking linear, side-chain liquid-crystalline polymers to networks
[ 1 lo]. The inherent combination of rubber elasticity and liquid-crystalline phase
behavior, may then be exploited for the induction of a macroscopic mesogen orientation
by mechanical deformation.
Liquid single crystal elastomers (LSCEs) are characterized by a high macroscopically
uniform orientation in the liquid-crystalline phase without the require-