99434-04-5Relevant academic research and scientific papers
Substituted Terminal Alkyl Groups and Their Prospects in Liquid Crystal Chemistry
Osman, Maged A.
, p. 353 - 360 (2007/10/02)
Polar substituents may be attached to the terminal alkyl groups of rodlike mesogens to increase their ε and to give a positive or negative Δε.The mesomorphic behaviour of some biphenyls, phenylcyclohexanes and bicyclohexanes with substituted alkyl groups was studied and compared to that of the corresponding unsubstituted compounds.In the first series no conclusive results could be obtained due to the relatively high melting points and low clearing points of the investigated compounds.In the phenylcyclohexanes and bicyclohexanes, substituents in ω-position were found to enhance the clearing temperature.In contrast, cyano groups in α-position depressed the clearing point.However, this depression is still much less than that caused by the introduction of lateral substituents in the phenyl moieties of the rigid core.
Aliphatic Liquid Crystals with Positive Dielectric Anisotropy
Osman, Maged A.,Huynh-Ba, T.
, p. 959 - 963 (2007/10/02)
Cyanoethyl-substituted cyclohexyl cyclohexanoates, bi(cyclohexanes) and phenyl cyclohexanes were synthesized.Their mesomorphic behaviour is compared to that of the corresponding cyano derivatives. (Cyanoethyl)cyclohexyl cyclohexanoates show mesomorphic properties in contrast to the corresponding cyano derivatives.Separation of the cyano substituent from the rigid core of an anisotropic aliphatic compound by methylene groups enhances the thermodynamic stability of its mesophase.In aromatic compounds, the cyanoethyl group leads to lower clearing points.These phenomena are attributed to the influence of steric effects on the packing density and to the dependence of the clearing point on molecular association.
