Effect of terminal branching on mesomorphism of a homologous series of Schiff base ethers

Abstract

A lot of studies have been focused on the Schiff base's alkyl and alkyloxy possessing polar terminal group. Yet, the thermotropic properties of Schiff base's ether (alkyloxy) with dialkylamino terminal group remained less studied. A series of 4-(dialkylamino)benzylidene-4'-alkyloxyanilines were prepared and all the members are differed by the alkyloxy chain length, CnH2n+1O, where n = 6, 8, 10, 12, 14, 16 and 18. Their transition temperatures and mesophase characteristics were studied by differential scanning calorimetry and optical polarizing microscopy techniques. DSC thermograms exhibited direct isotropization and recrystallization during heating and cooling cycles, respectively. The crystal phase texture changed to dark region isotropic without displaying any mesophase. Lengthening of dialkylamino terminal branch has caused depression of mesomorphic property in the compounds studied.