Effects of Lateral Substituents on Mesomorphic Behavior. IV. Phenyl 4-(4-Alkoxybenzylideneamino)-benzoates

Abstract

Phenyl 4-(4-alkoxybenzylideneamino)benzoates exhibit both a nematic phase and a smectic A phase when the alkyl chain is propyl to decyl. While the 2-X substitution tends to eliminate the smectic phase, the 3-X substitution tends to eliminate the nematic phase. A smectic A phase is generated by the methoxy to decyloxy members of the 3-Me, 3-F and 3-Cl derivatives, by the ethoxy and higher members of the 3-Br derivative and by the butoxy and higher members of the 2-F derivative. The smectic thermal stability can be enhanced or depressed by the 3-X substitution depending on the kind of halogen and the alkyl chain length; for example, 29°C for X=F, 3°C for Cl and −11°C for Br in the case of the propoxy member and 5°C for X=F, − 15°C for Cl and −24°C for Br in the case of the decyloxy member.

Key Words:

• lateral substituent
• nematic
• smectic