Tensors for Physics

284 15 Liquid Crystals and Other Anisotropic Fluids

0.5 0 0.5 1 1.5 2 2.5 3

a

0.5

0

0.5

1

1.5

2

F

Fig. 15.4 The Maier-Saupe graphical solution for the order parameter. Thethree straight linesare
for the temperaturesT/T∗= 1 .5, 1.0, and 0.75, fromlefttoright

Fig. 15.5The order
parametera=

√
5 Sversus
the temperatureTin units of
T∗.Thedashed partof the
curve corresponds to
unstable states

0. 7 0.8 0.9 1 1.1
   T

0.25

0.5

0. 75

1

1.25

1.5

1. 75

2

a

Fig.15.5lies at the slightly higher temperatureTni∗= 1. 114 T∗. For this temperature,
the straight line in Fig.15.4just touches the curve rather than intersecting it. At this
point, the order parameterais equal to 0.724 corresponding toS≈ 0 .33.

15.3 Elastic Behavior of Nematics

The elastic behavior of nematic liquid crystals and their great sensitivity to an applied
electric field play an essential role for the operation of liquid crystal displays (LCD).
The speed of switching a LCD is influenced by viscous properties, which are dis-
cussed in Sect.16.4.1.