Chemistry Reference
In-Depth Information
Fig. 18 Numerical (
closed symbols
) versus experimental (
open symbols
) results for (a) optical
birefringence (
Dn
) and (b) strain in the steady state (g
S
) as a function of voltage amplitude (
V
0
).
data for SNE-7 with the theoretical results using the fitted parameter values of
g ¼
4,100 J/m
3
. The theoretical value of reduced
birefringence
Dn
s
/
Dn
0
in the figure is given by cos
2
650 J/m
3
and
k
2
¼
0.0825,
k
1
¼
results describe the main features in the experimental data such as the presence of
the threshold for the onset of director rotation and the maximum value of strain at
high voltages. The theoretical strain reaches a maximum at y
¼
y
90
, where the
k
-1
). The
theoretical expression for the threshold field strength
E
g,c
for the gel is obtained
from (
22
) as:
s
birefringence becomes zero, and
j
max
is given by 3
g
/[2(1
g
þ g
)] (
1
r
k
1
e
0
e
a
E
g
;
c
¼
(23)
This equation gives a physical explanation for the threshold for director rotation.
The threshold is determined by field strength rather than voltage, and the director
starts to rotate when the dielectric force overcomes the strength of the memory of
the initial director at cross-linking.
The time courses of
Dn
eff
and g in response to field-on and field-off are computed
E
g
¼
5.9 and 8.8 MV/m. It should be noted that when selecting the material
parameter values, we first tune the parameters
g
,
k
1
, and
k
2
to fit the steady-state
(
g ¼
300 J/m
3
and
k
2
¼
6,000 J/m
3
), we tune the parameters
0.12,
k
1
¼
g
,
n
, and
2,000 J/m
3
. The
theoretical values of the rise times for the optical and mechanical responses are
compared with the experimental data in Fig.
16
. The model successfully describes
the t
on
Dn
~
E
g
-2
behavior in the experiments. In contrast, the model exhibits a
50 Js/m
3
,
12 Js/m
3
and
G ¼
G
to fit the dynamic data:
g
¼
n
¼
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