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Objective:High-protein diets (HPDs) are associated with greater satiety and weight loss than diets rich in other macronutrients. The exact mechanisms by which HPDs exert their effects are unclear. However, evidence suggests that the sensing of amino acids produced as a result of protein digestion may have a role in appetite regulation and satiety. We investigated the effects of l-phenylalanine (L-Phe) on food intake and glucose homeostasis in rodents.Methods:We investigated the effects of the aromatic amino-acid and calcium-sensing receptor (CaSR) agonist l-phenylalanine (L-Phe) on food intake and the release of the gastrointestinal (GI) hormones peptide YY (PYY), glucagon-like peptide-1 (GLP-1) and ghrelin in rodents, and the role of the CaSR in mediating these effects in vitro and in vivo. We also examined the effect of oral l-Phe administration on glucose tolerance in rats.Results:Oral administration of l-Phe acutely reduced food intake in rats and mice, and chronically reduced food intake and body weight in diet-induced obese mice. Ileal l-Phe also reduced food intake in rats. l-Phe stimulated GLP-1 and PYY release, and reduced plasma ghrelin, and also stimulated insulin release and improved glucose tolerance in rats. Pharmacological blockade of the CaSR attenuated the anorectic effect of intra-ileal l-Phe in rats, and l-Phe-induced GLP-1 release from STC-1 and primary L cells was attenuated by CaSR blockade.Conclusions:l-Phe reduced food intake, stimulated GLP-1 and PYY release, and reduced plasma ghrelin in rodents. Our data provide evidence that the anorectic effects of l-Phe are mediated via the CaSR, and suggest that l-Phe and the CaSR system in the GI tract may have therapeutic utility in the treatment of obesity and diabetes. Further work is required to determine the physiological role of the CaSR in protein sensing in the gut, and the role of this system in humans. more...

Sivaramakrishna Chandrasekhar died at the age of 73 years at his home in Bangalore. This sad news came from Chandrasekhar's daughter, Indira. She wrote: ‘My father had a mild heart attack followed by a stroke at the end of January, but he was recovering very positively. James, the children and I had been to see him only a few weeks ago. He was full of his usual enthusiasm and was planning various trips to conferences and meetings, and a paper on biaxial nematics, an idea that he had pursued for a long time, had just been accepted. It was a very happy visit. Since he was forced to slow down a little, he was able to relax and enjoy all the visitors who called on him. We were all shocked when he was struck down by a massive cerebral haemorrhage on the night of 7 March and are trying to face the grief and emptiness.’ As this sad news spread, the sorrow of Indira and of her brother Ajit, and that of Chandrasekhar's wife Ila, was shared by all working in the field of liquid crystals, to which Chandrasekhar had devoted his scientific talents and efforts since the 1960s. more...

Two new series of esters incorporating the 1, 4-disubstituted bicyclo(2.2.2)octane ring system are reported. Thirty-three 4-n-alkylphenyl 4-n-alkylbicyclo(2.2.2)octane-1-carboxylates and thirty 4-n-alkoxyphenyl 4-n-alkylbicyclo(2.2.2)octane-1-carboxylates have been prepared and found to exhibit wide-range nematic phases persisting until higher temperatures than those of the corresponding esters containing either the trans-1, 4-disubstituted cyclohexane ring or the 1, 4-disubstituted benzene ring in place of the bicyclo-octane ring. Mixtures of these novel bicyclo-octane esters with cyanobiphenyls have been found to be superior for multiplexing applications in twisted nematic cells to equivalent mixtures employing 4-n-alkylphenyl 4-n-alkoxybenzoates or 4-n-al-koxyphenyl trans-4-n-alkylcyclohexane-1-carboxylates. more...

Different substituents (fluoro, chloro, bromo, and cyano) have been separately introduced into the 2-position of the phenolic moiety of the 4-n-alkylphenyl 4-n-alkylbicyclo (2.2.2) octane-1-carboxylates to produce new series of low melting esters with large nematic ranges. In particular, thirty 4-n-alkyl-2-fluorophenyl and thirteen 4-n-alkyl-2-chlorlorophenyl 4-n-alkylbicyclo (2.2.2)octane-1-carboxylates are reported. The effect of the various lateral substituents on the clearing points and viscosities of the esters are rationalized in terms of steric interactions and the "shielding" properties of the bulky 1, 4 disubstituted bicyclo (2.2.2) octane ring. Mixtures of the 4-n-alkyl-2-fluorophenyl 4-n-alkylbicyclo(2.2.2)octane-1-carboxylates and cyanobiphenyls have useful electrooptical properties and have very low injected smectic tendencies. more...

Twelve 4-phenylbenzylidene-4'-n-alkoxyanilines have been prepared and their liquid crystal phases have been categorised. The properties of these compounds are compared with those of the analogous Schiff's bases, the 4-(4'-n-alkoxybenzylideneamino)biphenyls, in which the central imino-linkage is reversed. A structural factor that may be responsible for an unusual fan texture of the SB phase of Schiff's bases is suggested. more...

Recently1,2 the n-alkyl esters of the 4'-n-heptyloxy- to 4'-n-decyloxy-biphenyl-4-carboxylic acids (inclusive) were prepared. These homologous series all showed a sudden injection of smectic C properties at the n-butyl ester. In the current work, a number of esters of the 4'-n-dodecyloxy-4'-n-tetradecyloxy-, 4'-n-hexadecyloxy-, and 4'-n-octadecyloxy-biphenyl-4-carboxylic acids have been prepared in order to establish the smectic phase sequences at longer, terminal alkoxy chain lengths. It was found that, as the terminal alkoxy chain length was increased there was a natural, smooth progression to esters which exhibit tilted smectic B phases rather than tilted smectic C phases. more...

A single synthetic route for chain-deuteriated, totally ring-deuteriated, or per-deuteriated 4-n-alkyl-4'-cyanobiphenyls has been developed. This new route gives better yields than the previously reported route for the synthesis of 4-cyano-4'-n-pentyl-d11-biphenyl and also eliminates the main "impurity" present in the final product. The synthesis of 4-cyano-4'-n-pentyl-d11-2',3',5',6'-tetradeuteriobiphenyl is also reported. more...

A facile synthesis of S-(+)-4-(2'-methylbutyl)phenol and its interaction with a number of different acids are used to provide a wide variety of new chiral nematic liquid crystals. These new cholesterogens display a range of liquid crystal and other physical properties, and are potentially useful for application in display device and other technologies. Of particular interest in this respect are the materials containing two chiral centres and which therefore have very small helical pitch lengths-as low as 0.1 μm. more...

Thirteen 4', 4''-disubstituted phenyl biphenyl-4-carboxylates have been prepared and their liquid crystal transition temperatures measured. In each case, one of the substituents is a cyano-group and the nematic phases are of positive dielectric anisotropy. The potential of these esters to produce low melting eutectic compositions with a wide nematic range on admixture with simpler 4,4'-disubstituted phenyl benzoates is assessed in relation to requirements for electro-optical displays such as the twisted nematic type. more...

In recent years we have prepared a large number of mono-fluoro- and ortho-difluoro-substituted 4,4''-dialkyl- and 4,4''-alkoxyalkyl-terphenyls. The synthesis and transition temperatures of a variety of related difluoro compounds is presented here so that it is now possible to identify (i) broadening of the molecule, (ii) twisting about an inter-annular bond, and (iii) the presence of an 'inner' (2-, 2'-, 3'- or 2''-substituent) or an 'outer' (3- or 3''-substituent) fluorine, as being the major factors which influence the type and the thermal stability of the mesophases obtained. more...

A series of 4-cyanophenyl 4-X-benzoates and a series of 4-cyanobiphenyl-4'-yl 4-X-benzoates (X =pentyl, butoxy) have been prepared without fluoro-substitution and with mono-fluoro to tetra-fluoro-substitution; all possible combinations of substitution patterns at the positions ortho- to the cyano group and ortho- to the carboxylate group have been obtained in an attempt to determine the structural features which are responsible for some members of these series showing very large positive values of dielectric anisotropy. The synthesis of novel precursors required for the preparation of these esters is described and the melting points and transition temperatures of the esters are discussed and an explanation is provided for the variation of TN-1 values with position and extent of fluoro-substitution. more...

The synthesis and properties of a range of liquid crystalline side chain polysiloxanes are described. The effects of changes in chemical structure, such as lateral substitution, on the properties of these materials are discussed, and comparisons are made with the effects of similar structural changes in low molar mass materials. By selecting suitable side chains for homopolymers and copolymers, room temperature smectic, nematic and cholesteric (chiral nematic) polysiloxanes of positive dielectric anisotropy have been prepared, including the first example of a nematic siloxane homopolymer containing a cyano-group. more...

The preparation and liquid crystal properties of ten 4-n-alkylphenyl 2'-chloro-4'-(6-n-alkyl-2-naphthoyloxy) benzoates are described. The esters exhibit nematic phases of wide range.

The 2,6-naphthylene ring system has been used to replace each of the 1,4-phenylene rings in various 4-substituted-phenyl 4-substituted-benzoates, where the substituents were alkyl and/or alkoxy. For the dialkyl esters, the N-I temperatures were increased by 60-80° compared with the simpler, analogous phenyl benzoates, irrespective of the position of the 2,6-naphthylene ring. For the esters with one alkyl and one alkoxy substituent, the N-I temperatures were again higher than those of the corresponding phenyl benzoates (∼60°); SA properties were quite pronounced in the 6-alkyl-2-naphthyl 4-alkoxybenzoates. When both substituents were alkoxy groups, SC phases of quite wide thermal range were exhibited, usually preceded on cooling by a nematic and a SA phase. more...

Recently terephthalylidene-bis-4-n-pentyl-aniline (TBPA) was reported to have two types of tilted smectic B (smectic H) phase. However, our study of this material shows that this compound has a smectic F phase and a smectic H phase, and not two H phases as previously thought. more...

The transition temperatures of eight deuteriated, liquid crystalline derivatives of 4-cyanobiphenyl and four deuteriated liquid crystalline Schiff's bases are reported and compared with the transition temperatures of the corresponding non-deuteriated compounds. more...

Using only (-)-2-methylbutan-1-ol as an optically active starting material, other chiral aliphatic materials have been derived by synthetic procedures which preserve the optical activity, and a number of chiral mesogens incorporating the biphenyl (or p-terphenyl) ring system have been prepared. The new cholesterogens give a wide range of physical properties-melting points, cholesteric-isotropic liquid transition temperatures and pitch values. The twisting powers of the individual materials, i.e., the cholesteric pitch values, are related to the proximity of the chiral centre of the alkyl group to the ring system in which it is a substituent. Many of the compounds exhibit only cholesteric mesophases but some give additional smectic phases. The physical properties of the mesogens are assessed with particular reference to their applications in electro-optical displays or in surface thermography. In the latter case, the compounds provide a range of cholesterogens of good chemical/photochemical stabilities from which mixtures with thermochromic properties can be made. Examples are given of mixtures: with such materials, the sensitivity of colour play for a given mixture composition can be manipulated in a way which is not practical with sterol-type cholesterogens. With regard to the smectic properties exhibited by some of the compounds, of particular interest are those chiral smectic C phases which, as thin films in the planar texture, show iridescence colours through selective, temperature dependent reflection of light in the visible wavelength range. more...

The smectic properties are discussed for several series of esters which have the same "central core" molecular structure, i.e., [image omitted] The effects of just extending the carbon chain in a series of n-alkyl esters are discussed for the methyl to n-decyl esters of 4'n-decyloxybiphenyl-4-carboxylic acid. The effect on the inicidence of the smectic C Phase is quite striking. The butyl to hexyl esters inclusive exhibit this phase, while the heptyl to decyl esters show latent smectic C properties for which "virtual" transition temperatures can be obtained. The temperatures of SA to Sc transition lie on two parabolic curves, the even members lying on the curve representing higher Sc thermal stabilities than those of the odd members. The earlier homologues of the series show SA, SB, or SE or SAB properties. The effect on the incidence of the smectic phases was also investigated for molecules containing longer carbon chains. Here the incidence of the smectic C phase is discussed for the methyl to n-nonadecyl esters of 4'-n-octyloxybiphenyl-4-carboxylic acid. This series is roughly divided into three types, with the earlier homologues (methyl to propyl) showing SA, SB, SE, or SAB phases, the middle homologues (butyl to octyl) SA, Sc or Sc "virtual" and the later members (nonyl to nonadecyl) only SA phases. more...

A series of polysiloxanes having laterally-attached mesogenic side chains and involving variations in spacer length and the nature of the two end groups are reported. The terminally-attached analogues of some of these polymers are also reported. Optical microscopy and differential scanning calorimetry were used to establish the mesomorphic properties. An explanation is proposed for the low TN-1 values observed for the polymers with laterally attached side chains. more...

Advances in fields such as the applications, the physics, or the theory of liquid crystals depend very critically upon the organic chemist and his role in synthesising materials that, at the one extreme, are novel and imaginative enough to exhibit new and challenging phases or sequences of phase behaviour, or at the other extreme, have preselected molecular structures tuned to make some new application possible or to test some theory.A conference lecture of this kind provides a convenient opportunity to stress the importance of the organic chemist's role and to illustrate how his artistry is brought to bear in solving a range of materials problems.Several areas of progress are reviewed and used to illustrate how the development of new synthetic methods and reagents is enhancing the chemist's ability to respond to the needs of the liquid crystal community for highly pure compounds of growing structural complexity that have increasingly exacting physical properties and are frequently, today, also chiral and totally optically pure.One particularly important area is highlighted. This refers to developments in cross-coupling reactions, whereby routes to complex linear structures have been perfected and allow small manageable units, e.g., benzene derivatives in which substituents destined to be lateral groups are pre-positioned, to be used as the synthetic precursors that are then linked together in a convergent manner by palladium-catalysed processes and under conditions that are tolerant of many functional groups that may be wanted in the finished molecules.By such and other means, many mesogenic compounds that could only have been synthesised a few years ago by impossibly low yield processes, are now readily and economically available for study or applications. more...

Further to earlier work on the liquid crystal properties of fluoro-1,1':4',1"-terphenyls1 we have now extended this series to include terminally fluoro-and cyano-substituted 2'-fluoro-1,1':4',1''-terphenyls, chiral 2'-fluoro-1,1':4',1''-terphenyls, and esters derived from 2'-fluoro-1,1':4',1"-terphenyls and incorporating the alkylcyclobutyl group. The preparations and transition temperatures for these series of compounds are presented and their transition temperatures and mesophase types are discussed. An interesting result from this work was the appearance of an S*C phase for one chiral homologue and of Sc phases for the esters incorporating the alkylcyclobutyl group. The Sc formation is attributed to the presence of the fluoro-substituent.Keywords: terphenyls, fluoroterphenyls, smectic C phases, cyclobutyl esters more...

This paper describes the reasoning underlying the design and synthesis of a range of cyanohydrin esters, specifically as high Ps dopants of host SC materials, for use in fast switching ferroelectric displays. Full synthetic details are given for the preparation of optically pure cyanohydrin esters from naturally occurring L-amino-acids; examples derived from (a) a D-amino-acid, (b) lactic acid are also given. Such materials provide excellent dopants which in suitable SC hosts provide mixtures with wide S*C ranges, good Ps values and long pitches, which switch rapidly at room temperature and may be multiplexed at video frame rates. more...

The preparation of sixteen dimethylene linked compounds is described [14 incorporating the cyclobutane ring and 2 incorporating the spiro[3.3]heptane ring], and a comparison is made between the transition temperatures of these compounds and those of the corresponding esters.1 This comparison once again highlights the fact that the cyclobutane ring should be regarded, in terms of its ability to promote nematic thermal stability, as a "chain stiffener" rather than as a ring system.A comparison is also made of the nematic thermal stabilities of the trans-cyclobutane and the spiro[3.3]heptane systems and of the trans-cyclohexane and the spiro[5.5]undecane systems. more...

A large number of ferroelectric dopants incorporating a chiral lactate unit, [image omitted], have been synthesized and extrapolated values of Ps as high as 160 nC cm-2 have been found, although many of these compounds did not show any liquid crystal behavior. Terphenyls and laterally fluoro-substituted terphenyls incorporating the chiral lactate unit have also been synthesized, and in one case, a ferroelectric host material with an SC* phase and a Ps value of 124 nC cm-2 was obtained.Compounds containing two chiral units (one of which was a chiral lactate unit) were also synthesized in which the two chiral units were either directly linked or separated by a phenyl ring; the latter compounds gave very high Ps values (199 nC cm-2).The effect of molecular structure on Ps, tilt angle and phase behavior is discussed for both the mono-lactates and the di-chiral compounds.An outline (with references) of the experimental procedures used to prepare these compounds is also given. more...

Some new examples of injected smectic behaviour for binary mixtures of strong terminally polar mesogens (CBs, PCHs, BCOs, and CCHs) with a range of terminally non-polar esters are presented. Variations in the strength of the injected behaviour are discussed. Examples of SB as well as SA injection occur.Studies of mixtures of terminally non-polar 4,4''-dialkyl-2''-fluoro-p-terphenyls (I) with cyano-substituted mesogens are also described and provide an example of injection of SA and SE phases.Of greater interest is the observation that binary mixtures consisting solely of hom-ologues of (I) can exhibit reentrant nematic behaviour, providing further evidence that reentrant phenomena are not a special feature of terminally polar mesogens and their mixtures. An isomeric mixture of two compounds of structure (I) also gives an interesting case of an injected Sc phase, and enhanced Sc properties are recorded for other mixtures of homologues of (I).Mixtures involving alkyl/alkoxy analogues of (I) also provide examples of Sc phase injection or enhancement, and in one case some evidence for injected SI, behaviour. more...

Two polymeric water-soluble fractions were isolated by gel filtration after mild acid hydrolysis of the lipopolysaccharide from Pseudomonas aeruginosa N.C.T.C. 1999. The fraction of higher molecular weight retained the O-antigenic specificity of the lipopolysaccharide and may be ‘side-chain’ material. This fraction was rich in N (about 10%) and gave several basic amino compounds on acid hydrolysis; fucosamine (at least 2.8% w/w) was the only specifc component identified. The fraction of lower molecular weight was a phosphorylated polysaccharide apparently corresponding to ‘core’ material. The major components of this fraction and their approximate molar proportions were: glucose (3-4); rhamnose (1); heptose (2); 3-deoxy-2-octulonic acid (1); galactosamine (1); alanine (1-1.5); phosphorus (6-7). In the intact lipopolysaccharide this fraction was probably linked to lipid A via a second residue of 3-deoxy-2-octulonic acid, and probably also contained additional phosphate residues and ethanolamine. The residues of 3-deoxy-2-octulonic acid were apparently substituted in the C-4 or C-5 position, and the phosphorylated heptose residues in the C-3 position. The rhamnose was mainly 2-substituted, though a little 3-substitution was detected. The glucose residues were either unsubstituted or 6-substituted. Four neutral oligosaccharides were produced by partial acid hydrolysis and were characterized by chemical, enzymic, chromatographic and mass-spectrometric methods of analysis. The structures assigned were: Glcpα1-6Glc; Glcpβ1-2Rha; Rhapα1-6Glc; Glcpβ1-2Rhapα1-6Glc. The galactosamine was substituted in the C-3 or C-4 position, the attachment of alanine was indicated, and evidence that the amino sugar linked the glucose-rhamnose region to the ‘inner core’ was obtained. more...

A series of terminally cyano substituted side chain polysiloxanes have been characterized using optical microscopy, D.S.C., and X-ray diffraction. Values for the lamellar spacings, d, of the interdigitated smectic A phases were obtained, and the variations in d with temperature and length of the flexible aliphatic spacer are discussed. The spacing for m = 4, 5, and 6 increased regularly with m whereas the short m = 3 spacer gave an anomalously high value. more...

The so-called 'smectic' D phase of 4'-n-octadecyloxy-3'-cyanobiphenyl-4-carboxylic acid (one of only four materials known to exhibit this phase) has been shown unambiguously by X-ray diffraction to be characterized by a primitive cubic space group. The space group is either P23 or Pm3, and the lattice parameter a0 is 86 Å. It is shown that data from previous studies of this phase may be re-intepreted to be consistent with these findings. In view of these conclusions it is clearly inappropriate to refer to the phase as smectic. more...

Sixteen new side chain liquid polysiloxanes, either homopolymers derived from poly(hydrogenmethyl)siloxane or copolymers derived from poly(hydrogenmethyl-dimethylsiloxane), are reported with side chains carrying fluoro-substituents. The known effects of fluoro-substitution in low molar mass liquid crystals are strongly echoed in the polymeric analogues and interesting comparisons are made between homo- and co-polymers carrying the same fluorinated side chains. more...

A number of side chain liquid crystal polysiloxanes prepared from both homo-and co-polymeric backbones have been studied by 29Si N.M.R. and the chemical shifts assigned. Partly mesogenated poly(hydrogenmethylsiloxanes) have been similarly studied and chemical shift assignments made for sequence distributions. The data should prove helpful in studies of compositional variation in preparations of side chain copolymeric polysiloxanes. more...

The liquid crystal properties of a homologous series from methyl to heptyl of novel I-(trans-4-alkylcyclohexyl)-2-phenylethanes (PECH) are presented. These compounds are stable materials of low viscosity and low dielectric anisotropy incorporating the -CH,CH,- inter-ring linkage. Comparisons are made between the propyl homologue, PECH 3.H, and the commercial isomeric material PCH 3.2. The effect of replacing the trans-cyclohexane ring with a bicyclo(2.2.2)octane ring is discussed. A reversed PECH system, in which the alkyl chain is attached to the aromatic moiety (mono-substituted cyclohexane ring), was prepared. An analogous mono-substituted cyclopentane system was also investigated. The separation of two polar/highly polarisable functions in a molecule by a non-polar, non-conjugated group is known to have a detrimental effect on the liquid crystal thermal stability. A collection of data exemplifies this effect which is discussed simply in terms of molecular bonding principles. more...

A number of side-chain liquid crystal homopolymers derived from poly-(hydrogenmethylsiloxane) and their copolymeric analogues with the same mesogenic side chains appended to a poly(hydrogenmethyldimethylsiloxane) backbone have been prepared. The homo and copolymers exhibit the same mesophase types, but markedly different Tg values, mesophase transition temperatures and isotropisation enthalpies. These differences are interpreted in terms of the relative DP values and flexibilities of the backbones for the homo and copolymers. more...

X-ray diffraction has been used to study the nematic phases of the cis and trans isomers of an elongated molecule containing the cyclobutane group. It has been shown that these nematic phases consist of a mixture of single molecules and overlapping core dimers. It has been found that increasing the temperature of the cis isomer rapidly reduces the dimer population, whereas increasing the temperature of the trans isomer enhances the dimer population. This provides an explanation of the relatively high clearing temperature of the trans isomer. The different temperature dependences of the dimer population in the cis and trans isomers has been explained by a model involving inversion of the cylobutane group. more...

Three side chain liquid crystal polymers have been studied by neutron scattering methods. We have compared the three compounds, all with a polysiloxane backbone, a four-atom flexible spacer, (CH2)3O, and a benzoate ester mesogenic unit. However, the mesogenic unit was terminated by one of three different groups. The hexyloxy and cyano derivatives gave smectic A phases and the methoxy gave a nematic. Small angle neutron scattering measurements of mixtures of deuteriated and hydrogenous versions of the same polymer have been used to determine the dimensions and anisotropy of the backbone. The anisotropy was found to be similar in the smectic and nematic phases and suggested a tendency for the polymer backbone to be confined between the layers of mesogenic units. The SANS results show two different characteristic sizes. One is attributed to the size of a single polymer molecule. The other indicates density fluctuations on a scale larger than one polymer molecule. The local packing of the mesogenic units has been studied by comparison of neutron Bragg scattering from the smectic layers in materials with specific parts of the mesogenic units deuteriated. This has allowed the degree of interdigitation of mesogenic units in different layers to be deduced in the hexyloxy compound. It was found necessary to postulate a chain rich region midway between the polysiloxane backbones. This could only occur if the mesogenic units were significantly statistically tilted with respect to the smectic layer normal. more...

The N-I transition temperatures for a range of 4-propyl 1-monoesters and several 1,4-diesters of cubane, bicyclo(2.2.2)octane, cydohexane and benzene have been determined. The differences between the values for the monoesters and diesters of each system and between those for the various ring systems for the mono- and di-ester series are discussed. Cubane has a very poor ability to generate nematic phases of high thermal stability, and the relative nematic stability of the benzene derivatives are significantly different in the two series, the diesters with a central benzene ring having the highest N-I transition temperatures. The values for diesters and monoesters of dihydrocubane are compared with those for cubanes and the effect of deviations from colinearity of the substituent bonds and of changes in flexibility are discussed. more...

A chiral center has been introduced into different positions of one of the terminal alkyl chains of the known 4-alkylphenyl, 4-alkoxyphenyl and 4-alkyl-2-fluorophenyl 4-alkylbicyclo(2.2.2)octane-1-carboxylates1.2 to produce seven homologous series of esters possessing cholesteric phases. Several of the esters exhibit enantiotropic cholesteric phases of tight pitch at and above room temperature, whilst others exhibit longer pitch enantiotropic cholesteric phases (sometimes at room temperature) which reflect light in the visible region of the electro-magnetic spectrum and are thermochromic. more...

A number of esters and other compounds containing a trans-1,4-substituted cyclohexane ring system-have been prepared, and the liquid crystal thermal stabilities of these new mesogens are discussed in relation to those of their analogues containing the 1,4-phenylene ring. The observed effects are discussed in terms of a possible thermal energy absorption by the cyclohexane ring in causing minor conformational changes.Other physical properties of these new mesogens are also discussed with particular reference to their potential in applications. In relation to electro-optical display devices, such properties as birefringence, dielectric anistropy, viscosity etc., are important parameters, and the new materials have been assessed in this context as possible additives to the 4-n-alkyl- and 4-n-alkyloxy-4'-cyanobiphenyls for producing a favorable combination of physical parameters.Also reported is a liquid crystal mixture which has a 100°C nematic range and which contains only materials which are aliphatic. This mixture is assessed for its potential application as an anistropic solvent in analytical techniques such as ultra-violet spectroscopy and nuclear magnetic resonance spectroscopy. more...

The preparation of pure crystalline cholsteryl oleyl carbonate is described. The melting point, the mesophase transition temperatures, and the enthalpy of the melting process are recorded, and a method of maintaining cholesteryl oleyl carbonate in a pure state over extended periods of time is suggested. more...

Re-examination of the bis-(4'-n-alkoxy-benzylidene)-1,4-phenylenediamines, particularly the heptyloxy homologue, by optical microscopy and differential scanning calorimetry has confirmed the existence of two hitherto unclassified smectic phases, which are now assigned the code letters J and K (SJ andSk more...

A preliminary study of the properties of nine cyanoaryl esters of various 40-alkylbicyclo [2.2.2] octane-carboxylic acids has been extended and results are now presented for a wider range of 4-cyanophenyl, 2-cyano-6-naphthyl, and 4-cyano-4-biphenyl 4-alkylbicyclo [2.2.2]octane-1-carboxylates. more...

Three areas of research into liquid crystals which have seen considerable development since the last International Liquid Crystal Conference at Bordeaux in 1978 have been selected for a brief over-view.These areas concern: New Liquid Crystal Materials containing non-aromatic ring systems and the developments which have followed from the earlier studies of esters of trans-4-n-alkylcyclohexane-1-carboxylic acids and the trans-4-n-alkyl-l-(4'-cyanopheny1)cyclohexanes (PCH's). Agreement over a Nomenclature Problem Concerning Smectic Polymorphs and some interesting features of the smectic phase sequences for the 4-n-alkoxybenzylidene-4'-n-alkylanilines. Discotic Phases - the discovery that the historically well known mesophase of di-isobutyl-silandiol is a discotic liquid crystal phase and the progress being made in studies of other discotic systems. more...

The first indication that terphenyl derivatives might provide suitable host Sc systems which could be doped with chiral materials and used in ferroelectric smectic C devices arose with 4,4''-dialkyl- and 4,4''-alkoxyalkyl-p-terphenyls carrying a single lateral fluoro-substituent. Subsequently, 4,4''-dialkyl- and 4,4''-alkoxyalkyl-p-terphenyls with 2,3- or 2',3'-difluoro-substituents (and related biphenyls) have been found to be superior, when doped with appropriate chiral cyanohydrin esters. The synthesis of these difluoro-oligophenyls will be discussed, with particular reference to the use of tetrakis(triphenylphosphine)palladium(0)-catalysed coupling of arylboronic acids with aryl halides.The liquid crystal properties of the various materials will be discussed together with some results relating to the excellent ferroelectric behaviour of the doped systems. These mixtures provide wide range S*c phases, large Ps values, good aligning properties on rubbed polymers, switching times that are fast, and a multiplexing capability consistent with video line address times at room temperature. more...

Di(5-alkylsalicylidene)ethylenediaminato nickel(II) and copper(II) complexes have been synthesized and investigated. They show similar behaviour to the corresponding alkyloxy-substituted complexes - wide mesophase ranges and calamitic smectic phases. The thermal stability of the nickel(II) complexes is higher than that of the copper(II) complexes.The title compound crystallizes with one water molecule per formula unit (water - diethyl ether interface) and Z = 4 in space group P21/c. X-ray crystal structure analysis shows that the molecular skeleton with the exception of the ethylene bridge is essentially planar and adopts a maximum stretched form. The crystal packing is characterized by a herringbone arrangement of columns of centrosym- metrical pairs of molecules. more...

A number of esters of structure (I) incorporating the cyclobutane, spiro[3.3]heptane, or dispiro[3.1.3.1]decane rings has been prepared using a diethyl malonate synthesis. Strict comparison of the liquid crystal behaviour amongst the three classes containing a terminal cyano-substituent was not possible because both the cyclobutanes and dispiro[3.1.3.1]decanes are mixtures of cis- and trans-isomers; the spiro[3.3]heptanes are racemic systems. Using preparative hplc, it was however possible to isolate the pure cis- and trans-isomers of two of the cyano-substituted cyclobutane esters (I; R = alkyl, - × - = [image omitted], Y = CN). From the physical data and the results for the corresponding spiro[3.3]heptane esters, conclusions regarding the effects of these ring systems on liquid crystal behaviour were obtained.The pure cis- and trans-isomers of the cyclobutane ester (I, R = C3H7, - × - = [image omitted], Y = CN) have been assessed for the trends in both order parameter and viscosity with temperature; the results support the idea that the trans-cyclobutane ring adopts a more planar conformation at higher temperatures. more...

A variety of one-ring, two-ring, and three-ring esters incorporating one or two 1.4-disubstituted bicyclo(2.2.2)octane rings has been synthesised. In some cases the esters are fully alicyclic, e.g., terminally alkyl substituted alkyl bicyclo-octanoates, bicyclo-octyl bicyclo-octanoates and bicyclo-octyl cyclohexanoates. In others, the acidic moiety consists of one or two benzene rings or a benzene ring linked to a cyclohexane ring. The range of esters also includes some alkyl and bicyclo-octyl esters in which the acidic moiety contains a bicyclo-octane linked to a benzene ring system. The transition temperatures for the different types of ester are reported and compared with one another and with literature values for related esters.Results obtained from measurements of viscosity, birefringence, and electro-optical characteristics on some of the fully alicyclic esters are also reported. more...

The preparation and mesomorphic properties of a number of 1-n-alkyl-4-(4-n-alkyl- and 4-n-alkoxy-phenyl)bicyclo(2.2.2)octanes and 1-n-alkyl-4-(4'-n-alkylbiphenyl-4-yl)bicyclo(2.2.2)octanes are described. The clearing temperatures reported emphasise the high thermal stability conferred upon liquid crystal phases by the presence of the bicyclo-octane ring in a mesogen. Some physical data relating to the use of such materials in mixtures for electro-optical displays have been obtained. more...

Several 1,4-di-n-alkylbicyclo (2.2.2) octanes ((4), dialkyl BCO) have been prepared and virtual TN-1 values and extrapolated viscosities are reported. Their TN-1 values are markedly dependent on the nature of the host, but the ability of the BCO unit to give derivatives of relatively hight TN-1 is confirmed; the viscosities of the dialkyl BCO derivatives in various host mixtures are given and compared with the values for other low viscosity additives. 1-n-Alkyl-4-n-alkoxybicylco (2.2.2) octanes and 1-n-alkyl-4-n-alkoxybicyclo(2.2.2) octan-2-ones, (5) and (6) respectively, have also been prepared and the effect of the ether carbonyl functions on the TN-1 values is discussed. An outline of the synthetic routes to (4), (5) and (6) is given. more...