E. S. R. study of some 4-methoxybenzilidene-4'-amino-n-alkyl cinnamates

Abstract

Nitroxide spin probes dissolved in compounds of the homologous series 4-methoxybenzilidene-4'-amino-n-alkyl cinnamate are used for E. S. R. studies of the order parameter in oriented nematic and smectic mesophases. Comparison between experimental results and McMillan's theoretical predictions for the smectic A ↔ nematic transition allows one to show the important role taken by the alkyl end-chain at such a transition