Mesomorphic properties and molecular structure. II. Structure of the smectic A phase in the 4-propionyl-4' -n-alkanoyloxy-azo-benzene series

Structural parameters concerning the smectic A phase in homologues of the 4-propionyl-4'-n-alkanoyloxy-azo-benzene series have been obtained by using dilatometry and X-ray diffraction techniques. The comparison with the data of the previously investigated homologues of the 4-acetyl-4'-n-alkanoyloxy-azo-benzene series suggests that the same model can be adopted for both series with some modifications regarding the spreading of the aliphatic chains and the tilt angle of the aromatic cores. Experimental evidence for the tilt angle of the rigid part of smectogenic molecules in the smectic A phase is discussed in relation to the chemical constitution and molecular architecture Les parametres structuraux concernant la phase smectique A des homologues de la serie du titre sont obtenus par dilatometrie et par diffraction RX. La comparaison avec les donnees de la serie equivalente acetyl-4, montre que pour les deux series on peut adopter le meme modele sous reserve de quelques modifications concernant le degre de desorganisation des chaines aliphatiques et l'angle d'inclinaison des parties polaires des molecules