Liquid crystalline properties of dissymmetric molecules VI. The effect of alkyl chain length on molecular arrangement in the smectic A phase in three-aromatic-ring systems with two ester groups

• Published in: Liquid crystals Vol. 28; no. 7; pp. 1025 - 1034
• Main Authors: Tasaka, Takeyasu, Okamoto, Hiroaki, Petrov, Vladimir F., Takenaka, Shunsuke
• Format: Journal Article
• Language: English
• Published: Taylor & Francis Group 01.07.2001
• ISSN: 0267-8292; 1366-5855
• DOI: 10.1080/02678290110045906

The effect of alkyl and alkoxy chain lengths on the layer structures of smectic A and C phases has been examined by X-ray diffraction measurements on three isomeric systems: 4-alkoxyphenyl and 4-n-alkylphenyl 4-[(4-octyloxyphenyl)carbonyloxy]benzoates (1); 4-octyloxyphenyl 4-[4-(octyloxyphenyl)carbonyloxy]benzoates (2); 4-octyloxyphenyl, 4-alkoxyphenyl and 4-n-alkylphenyl terephthalates (3); and p-phenylene 4-octyloxybenzoates, 4-alkoxybenzoate and 4-n-alkylbenzoate (4). Although all the derivatives exhibit smectic A and/or C phases having a monolayer arrangement of the molecules, the layer spacings are considerably affected by alternation of the ester linkages. The layer spacings for the homologues of 1 are a little shorter than the calculated molecular lengths, while those for 2 agree with the calculated molecular lengths. The layer spacings for 3 show a notable even-odd alternation in the higher homologues. The results are discussed in terms of a subtle change in the molecular structures due to replacement of the ester groups.