E. Chin

A Protection-Deprotection Method for the Synthesis of Substituted Benzoyloxybenzoates

Abstract Common syntheses of phenyl benzoyloxybenzoates generally produce products in low yields. A variety of synthetic pathways were employed in an attempt to increase the overall yield of the final product. It was found that catalytic agents such as boron trifluoride-etherate (BF3 Et2O), 1,3-dicyclohexylcarbodiimide (DCC), and 4-N, N-di-methylaminopyridine (DMAP) were relatively ineffective in these processes. However. protection of the hydroxy moiety of an appropriately substituted benzoic acid with methyl chloroformate, followed by esterification under normal conditions, and deprotection with ammonia in ethanol produces the hydroxy-benzoyloxybenzoate intermediate. This material can be used in further esterifications to produce phenyl benzoyloxybenzoate compounds in good yield. Materials such as the triply reentrant compound 4-n-nonyloxyphenyl 4-nitrobenzoyloxybenzoate (DB9ONO2) can be prepared by this method.

A chiral induced ferroelectric liquid crystal phase transition with a vanishingly small enthalpy

Abstract Information on molecular interactions that give rise to the stabilization of various ferroelectric, liquid-crystalline mesophases is important to the realization of their potential utility in a wide variety of optical devices. Understanding the roles that optical activity and optical purity play in the formation and properties of the various smectic phases is therefore of particular interest. In order to study this relationship three new liquid-crystalline materials were prepared, one as a racemic mixture, the other two as the optically active analogues. The optically active isomers appear to exhibit a different mesophase morphology from the racemate. The chiral compounds apparently possess two extra ferroelectric mesophases in comparison to the racemic mixture. The transitions to and from these phases have extremely small enthalpies. An attempt is made to explain the results for the chiral compounds in terms of differing dipolar couplings in the chiral ferroelectric phases. In the racemic mixtur...

The ferroelectric and liquid-crystalline properties of some chiral alkyl 4-n-alkanoyloxybiphenyl-4′-carboxylates

A variety of chiral esters of a range 4-n-alkanoyloxybiphenyl-4′-carboxylic acids have been prepared in order to produce three closely related homologous series of liquid-crystalline materials. The majority of the materials synthesized were found to exhibit smectic liquid-crystalline phases close to room temperature. Many of these phases were also found to be ferroelectric. Moreover, the ferroelectric behaviour observed was found to be very unusual, and in the case of some materials a peculiar change in sign of the spontaneous polarization direction with temperature was detected.

Liquid-Crystalline Derivatives of S-3,7-dimethyloctan-1-ol

Abstract A wide variety of liquid-crystalline derivatives of S-β-citronellol (S-3,7-dimethyloct-6-ene-1-ol) were prepared and found to exhibit ferroelectric smectic phases. The S-β-citronellol was initially hydrogenated to produce S-3,7-dimethyloctan-1-ol (3M7M8OH). This in turn was either brominated, oxidized, or used in an unchanged form to synthesize a range of materials, many of which exhibited smectic C* phases. The magnitude of the spontaneous polarization for a number of these derivatives was measured. Generally, the materials reported were found to have values for their spontaneous polarizations in the range of 5 to 15 nCcm−2. Many of the materials were also found to have short helical pitches in their C* phases, making them useful as unwinding agents in ferroelectric mixtures.

The Liquid-Crystalline Properties of Some Chiral Derivatives of the 4-n-Alkanoyloxbiphenyl-4′-Carboxylic Acids

Abstract A variety of chiral derivatives of some 4-n- alkanoyloxybiphenyl-4′-carboxylic acids were prepared in order to produce a number of structurally related homologous series of compounds. In this systematic study, the synthesis of a number of chiral 2-chloropropyl, 3-chlorobutyl, alkylether, and 1 -methylalkyl esters of these acids are reported. The liquid-crystalline and ferroelectric properties of these materials were also investigated and the results obtained are compared with those previously established for the closely related 1 -methylpropyl, 2-methylbutyl, and 3, 7-dimethyloctyl esters of the same acids.

Ferrielectric and antiferroelectric properties of a fluoro-substituted biphenyl ester

The material (R)-1-methylheptyl 4-(4′-n-dodecyloxybiphenyl-4-ylcarbonyloxy)-3-fluorobenzoate has been prepared and its liquid-crystalline properties investigated. This material was selected for synthesis because it was expected to exhibit a ferroelectric smectic C* phase with a large value for its spontaneous polarization. Moreover, as the material carries a terminal peripheral chiral 1-methylheptyl moiety it was also expected to exhibit strong chirality-dependent properties. Thus, the material was also found to possess ferrielectric and antiferroelectric modifications in addition to the normal ferroelectric phase. In particular, the ferrielectric phase was found to exhibit unusual behaviour in the presence of applied electric fields.

The effect of structural changes in the molecular core and periphery on the liquid-crystalline properties of some chiral 4-n-alkoxyphenylpropiolates

Abstract The thermotropic liquid-crystalline properties of several homologous series of chiral 4-n-alkoxyphenylpropiolates were correlated with chemical structural modification on the periphery of the rigid, aromatic, molecular core. The temperature ranges of the most disordered mesophase in each series were shown to be inversely proportional with respect to the number of carbon atoms in the terminal alkoxy moiety. The type of mesophase exhibited by an homologous series is determined by the number of carbons in the chiral alkyl substituent. Homologous series containing short chain chiral alkyl substituents formed mesophases that had higher degrees of disorder (i.e. cholesteric phases) than did those that contained long chain chiral alkyl substituents.