- Phase Transitions in N(p-n-Butoxybenzylidene)p-n-Alkyl Anilines: Densitiy and Refractive Index Studies
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The density and refractive index variation with temperature in N(p-n-butoxybenzylidene)p-n-alkylanilines viz., 4O.m compounds for m = 4 to 12 are presented.The density, thermal expansion coefficient and the refractive index results infer first order character for IN, AB and CB transitions and a second order character for NA and AC transitions.Pretransitional effects are discussed at IN and AB transitions.The odd-even effect is observed at both the IN and NA phase transitions.The variation of refractive index anisotropy as a function of temperature, in the nematic phase of the compounds in a homologous series has shown an interesting p henomena.The temperature dependence of nematic refractive index anisotropy yields mean field exponent ν = 1 in the vicinity of NA transition.The influence of molecular chemical constitution, the nematic thermal range and the McMillan parameter values on the order of NA transition is discussed in detail.
- Rao, N. V. S.,Potukuchi, D. M.,Pisipati, V. G. K. M.
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- RECHERCHES SUR LES SUBSTANCES MESOGENES-VIII; PREPARATION ET PROPERTIES MESOMORPHES DE SERIES ISOMETRIQUES
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The synthesis and the mesomorphic properties of various series of isometric mesogenic compounds are described.It is confirmed that isometric mesogenic molecules may be nematogenic and/or smectogenic according to the position of the polar rigid core.
- Malthete, Jacques,Canceill, Josette,Gabard, Jacqueline,Jacques, Jean
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p. 2815 - 2821
(2007/10/02)
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- Organic thermotropic nematic compounds
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A new family of organic thermotropic nematic compounds comprising N-(para-substituted alkoxy-benzylidene)-anilines having also a para-n-butyl substituent on the aniline ring. These compounds have the following structural formula: STR1 wherein R is a straight chain alkyl group containing 1 to 4 carbon atoms and R' is n-butyl. Synthesis involves combining the desired p-substituted benzaldehyde and p-n-butyl aniline in equimolar proportions in anhydrous ethyl alcohol with glacial acetic acid as catalyst. The resulting homologous series of compounds are useful as materials which undergo a change in optical properties under the influence of externally applied energy, preferred members of which, either individually or in binary mixtures, have melting points near room temperature, a broad nematic mesomorphic temperature range within an overall range of about 0° to about 70° C., low viscosity in the nematic phase, good stability, and substantially no color.
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