Chemistry Reference
In-Depth Information
liquid states with T
sol-gel
4T
iso-lc
, enhanced functionalities can be displayed.
For example, a discotic LC physical gel synthesised combining a hole-
transporting triphenylene LC derivative and a biphenyl amino acid based gelator
was proved to form randomly disperse fibrous gel networks with microphase-
separated states of the triphenylene LC derivative (T
sol-gel
4T
iso-lc
)
35
(Figure 7.3).
In this LC physical gel a hole mobility three times higher than that of the
columnar LC structure alone was demonstrated by the introduction of micro-
phase separated structures into the discotic LC. It was assumed that the fibrous
gel network effectively suppressed the LC fluctuations, thereby leading to a faster
hole transport.
Additionally, liquid-crystalline polydomains formed from liquid-crystalline
physical gels with T
sol-gel
higher than T
iso-lc
have effectively been introduced as
reversibly switchable films with light-scattering functionalities. For example,
Smith and coworkers fabricated white-light-scattering films with a commercial
nematic LCs (LC-E7) and a sorbitol organogelator derivative
36
(Figure 7.4). In
this case, it was shown that electro-optically active cells formed by this LC
physical gel were reversibly switchable between a transparent and an opaque
state by applying alternating current (AC) electric fields (Figure 7.4). Upon
Liquid crystal
Gelator fibers
Light
(b)
Light
(a)
ON
OFF
electric field
Light scattering
Light transmitting
Figure 7.4
The molecular structure of a sorbitol organogelator derivative and sche-
matic illustrations (a and b) showing the switching between an opaque
state and the transparent state in a nematic LC gel, respectively. At the
bottom, pictures of the OFF (left) and ON (right) cell states.
