Effects of Polysubstitution on Mesomorphic Properties: Methyl Derivatives of 4- Alkanoyloxy-4′-ethoxy- and 4-(4-Alkoxybenzoyloxy)-4′-ethoxyazobenzenes

Abstract

The effects of methyl substituents placed in the 2- and/or 3-positions of 4-alkanoyloxy-4′-ethoxyazo-benzenes upon the nematic-isotropic transition temperature have been examined. While the 2- and 3- methyl derivatives exhibit transition temperatures lower by 50–55°C than the parent compound, the 2,3-dimethyl derivative exhibits a temperature higher by 20–30°C than either the 2- or 3-methyl derivative. Furthermore, the mesomorphic behavior of a complete set of mono-, di-, tri-, and tetramethyl derivatives have been recorded employing 4-[4-(decyloxy)benzoyloxy - and 4-[4-(dodecyloxy)benzoyloxy −4′-ethoxyazobenzenesas the parent compounds in order to demonstrate the effects of methyl groups added to the central part of the three-ring system.

Key Words:

• liquid crystals
• nematic
• lateral methyl groups