ABSTRACT
More than 80,000 LC compounds have been found. One observes LC phases in:
• Organic compounds consisting of highly anisotropic molecules of rod-like conformation
• Polymers with high degree of rigidity in the backbone or side-chains • Polymers or associated molecules that form rigid-rod like structures
The molecules or groups of molecules that display LC order are called mesogens or mesogenic compounds. The first mesogen was found by Reinitzer (Austria) and Lehmann (Germany) in 1888, cholesteryl nonanoate (ester of cholesterol and nonanoic acid) (Figure 2). This compound displays two melting points:
Tm1 = 145.5 °C ⇒ cloudy liquid
Tm2 = 178.5 °C ⇒ clear liquid
The organic compound 4-methyloxybenzylidene – 4’-butylaniline (MBBA) (Figure 3) was the first compound found that displayed liquid crystallinity at room
temperature (Kelker and Scheurle, 1969).
