Chemistry Reference
In-Depth Information
(a)
(b)
Figure 1.11.
The discotic nematic (a) and column phases (b).
Figure 1.12.
An example of a typical disc-like molecule.
N
D
∗
phase. A phase similar to the rod-like smectic liquid crystal phase is
the column phase in which molecules are packed as columns parallel to each
other. The columns are arranged in a hexatic or rectangular array. Inside
the columns, the spacings of the molecules are either constant or random.
The axes of the columns may be tilted with respect to the normal of discotic
molecules. Figure 1.12 sketches the chemical formulae of one example of a
discotic liquid crystal molecule.
There is another class of liquid crystals, the bowlic liquid crystal phase,
whose molecules are bowl-like or pyramid-like, as is shown in Figure 1.13.
Because of the breaking down of the up-down symmetry, the bowlic phase
shows an even higher order and may be able to show ferroelectricity (Lam,
1986; Wang
et al.
, 1989).
