Chemistry Reference
In-Depth Information
1.0
8
Boundary Conditions:
1) E+ :
θ
(0) = 0
;
θ
(1) =
π
/2
2) E- :
θ
(0) =
π
3) D
c
;
/2
;
θ
(1) =
π
/2
θ
(1) =
π
6
:
θ
(r
c
) =
π
/2
4
1
2
Shear thickening slope
2
0.135
0.184
0.270
100000 1000000
3
0.1
0.01
0.1
1
10
100
1000
10000
Ericksen number
Figure 2.19
Dimensionless apparent viscosity (
η
) as a function of the Ericksen
number. Er for the escaped (1:
E
+
and 2:
E
−
) and (3:
D
c
) onion textures. [Adapted from
de Andrade Lima and Rey (2004e) .]
TABLE 2.3 Comparison of Orientational Diffusivity Coeffi cients of
Surfactant Nematic Calamitic (N
c
) and Disklike (N
d
) Nematic Phases
with a Thermotropic Calamitic (MBBA)
Calamitic
Thermotropic
MBBA
T
Orientation
Diffusivity
D
0,
j
(m
2
/s)
Calamitic N
c
(LDhW)
T
Discotic N
d
(LDhW)
T
Discotic N
d
(DHCDhW)
T
=
29.4 ° C
=
19 ° C
=
29.4 ° C
=
25 ° C
D
0,splay
∼ 0.5 × 1 0
− 12
11.5 × 1 0
− 12
4.5 × 1 0
− 12
5 6 × 1 0
− 12
D
0,twist
∼ 0.42 × 1 0
− 12
1.6 × 1 0
− 12
0.30 × 1 0
− 12
4 3 × 1 0
− 12
D
0,bend
10.7
×
1 0
− 12
—
0.33
×
1 0
− 12
430
×
1 0
− 12
D
0,splay
/
D
0,twist
∼
1
7.2
15
1.3
25
1
1.1
10
D
0,bend
/
D
0,twist
Source
: Adapted from Santos and Amato (1999) .
laureate/decanoe/D
2
O (N
c
), DHCDhW (N
d
) were compared with MBBA, an
N
c
thermotrope; see Table 2.3 .
Table 2.3 shows that the anisotropy in thermotropic and lyotropic N
c
phase
is similar:
DDDD
o splay
C
≈
C
C
>>
C
(2.54)
,
o twist
,
o bend
,
o twist
,
which is attributed to the fact that splay backfl ow is weak while bend backfl ow
is strong:
αη
2
<<
αηγ
2
,
>>
η
bend
. On the other hand, for N
d
lyotropic
3
1
2
21
phases the anisotropy is reversed:
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