Biomedical Engineering Reference
In-Depth Information
h e structures were free of defects. h e material was highly elastic over a
wide range of temperatures.
In polymer
58
, poly(ethylene oxide)-
block
-poly(L-lysine) was com-
plexed with HBC. h ese thermotropic liquid crystals exist in two phases:
Col
h1
and Col
h2
. It was found that the poly(L-lysine) blocks form an
α-helical secondary structure. Each helix is surrounded by six discotic col-
umns of HBC, which gives an α-helical-within-discotic column structure
entity. h e transition from Col
h1
to Col
h2
on heating was found at 54 C
while on cooling at -30 C. h e larger unit cell size of Col
h2
was explained
by a higher intracolumnar order in the latter.
9.3.1.9 4,4-Dil uoro-4-bora-3a,4a-diaza-s-indacene (BODIPY)
Complexes
59a-g
formed (Figure 9.22) by means of ion association
between sulfobodipy
2-
and imidazolium- or ammonium-based cations in
stoichiometry of 1:2 have been studied for their mesomorphic properties
[87, 92]. It was found that ammonium-based complexes
59a-c
decom-
posed above 180 C. But they exhibited Col
h
phase over a wide range of
temperature (Table 9.10). h e amido subunit in the ammonium cation
was found to be engaged in supramolecular H-bonding. Compounds
59d-f
were also found to display Col
h
phase. But, the salt containing the
gallate functionalized imidazolium cations (
59g
) showed no mesomor-
phism. However, the acrylate units can be used to engender photoiniti-
ated polymerization.
OC
n
H
2n+1
O
OC
n
H
2n+1
N
H
X
OC
n
H
2n+1
59a-c
OC
n
H
2n+1
OC
n
H
2n+1
X
N
+
X
-
O
3
S
SO
3
X
+
N
N
N
OC
n
H
2n+1
B
F
F
59d-f
O
59
O(CH
2
)
11
O
X
OC
12
H
25
N
O
N
O(CH
2
)
11
O
59g
Figure 9.22
BODIPY sulfonate ionic liquid crystal.
