The tetrakis(triphenylphosphine) palladium (0)-catalysed coupling of arylboronic acids with aryl halides is used to prepare several 4,4″-dialkyl- and 4,4″-alkoxyalkyl-1,1′:4′,1″-terphenyls 2,3- or 2′,3′-difluoro substituents their related biphenyl systems. Lithiation ortho a 1,2-difluoroaromatic unit provides the route 2,3-difluoroarylboronic acids.The 2,3-difluoro substituted terphenyls are low-melting liquid crystals wide-range Sc phases no underlying smectic phase; these compounds...

The Fermi level at the Ga oxide/GaAs interface has been unpinned by rf plasma cleaning GaAs surface in H2 and N2. Following cleaning, a oxide film is reactively electron beam deposited onto substrate. Metal-oxide-semiconductor (MOS) capacitors fabricated on these structures show good high-frequency capacitance-voltage characteristics. This indicates that density of states reduced to ∼1011 eV−1 cm−2. MOS are found be stable air after several months.

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

A number of laterally fluorinated 4,4″-di-n-alkyl-, 4,4″-di-n-alkoxy- and 4-n-alkyl-4″-n-alkoxy-l,r:4′,1″-terphenyls structure (I) have been synthesised, with the lateral fluoro-substituent in central benzene ring. The nematic smectic thermal stabilities for all three series compounds, examined. typical example is (I), X = n–C5 HU, Y n–C3 H7, C–N 50°C N–I 140.6°C. For 4,4″-di-n-alkyl-1,1′:4′,1″-terphenyls, position respect to longest n-alkyl chain found be important determining behaviour...

Abstract A large number of laterally fluorinated 4-n-alkyl- and -alkoxy-phenyl 4'-n-alkyl- -alkoxy-benzoates 4-n-alkylphenyl trans-4'-n-alkyl- -alkoxy-cyclohexane-1-carboxylates were synthesised. In these compounds, the lateral fluoro-substituent was situated in either phenol or carboxylic acid moiety molecules for benzoate esters, but only moeity trans-cyclohexane-1-carboxylate esters. The nematic thermal stabilities fluorophenyl esters fiuorobenzoate compared with those corresponding...

Abstract A series of 4-cyanophenyl 4-X-benzoates and a 4-cyanobiphenyl-4′-yl (X =pentyl, butoxy) have been prepared without fluoro-substitution with mono-fluoro to tetra-fluoro-substitution; all possible combinations substitution patterns at the positions ortho- cyano group carboxylate obtained in an attempt determine structural features which are responsible for some members these showing very large positive values dielectric anisotropy. The synthesis novel precursors required preparation...

Abstract The synthesis is reported of fifteen three-ring 2,5-disubstituted pyridines and two pyridine-N-oxides where the pyridine rings carry a variety alkyl, aryl, cyclohexyl, cyclohexylethyl fluorinated-aryl substituents. mesomorphic transition temperatures for these compounds have been measured; all show enantiotropic phases. different substituent effects are discussed comparisons made with previous work on analogous systems hetero-function replaced by C-F.

A simple theory of the dielectric relaxation dipolar mesogenic groups in a liquid-crystal environment is described. It shows that four modes which are active experiment arise from combinations certain time-correlation functions for angular motions nematic potential. Experimental data siloxane polymer reported wide ranges frequency and temperature different macroscopic alignments sample (homeotropic, planar). These analysed with aid theory, it shown director order parameter Sd, local S dipole...

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

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

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

Abstract Initial experimental evaluation of a novel liquid-crystalline polysiloxane for thermo-optical recording is presented. A versatile system using single laser source has been used to gather information on the dynamics addressing. To ensure most stable, highest-contrast pixel polymer must be heated through its biphasic region and some way into isotropic phase. It was found that at 60°C pulses 300μs or less, write-in selective erasure times were submillisecond timescale, bulk required...

Abstract Some new examples of injected smectic behaviour for binary mixtures strong terminally polar mesogens (CBs, PCHs, BCOs, and CCHs) with a range non-polar esters are presented. Variations in the strength discussed. Examples S B as well SA injection occur. Studies 4,4″-dialkyl-2″-fluoro-p-terphenyls (I) cyano-substituted also described provide an example A E phases. Of greater interest is observation that consisting solely hom-ologues can exhibit reentrant nematic behaviour, providing...

Cyclic poly(hydrogenmethylsiloxane) fractions [H(Me)SiO]x with 4 < x 24 (x= number-average degree of polymerisation) have been prepared by a pyrolysis reaction and interacted suitable mesogenic alkenes to form liquid crystalline cyclic polymers; some the properties these polymers are reported here compared those their open chain analogues.

Abstract 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 4,4″-dialkyl- 4,4″-alkoxyalkyl-p-terphenyls carrying a single lateral fluoro-substituent. Subsequently, 2,3- or 2′,3′-difluoro-substituents (and related biphenyls) have been found to superior, when appropriate cyanohydrin esters. synthesis of these difluoro-oligophenyls will discussed, particular reference...

Abstract The removal of the alkene side‐chain precursor from liquid‐crystal (1.c.) polysiloxanes during their isolation by precipitation has been monitored thin‐layer chromatography. commonly used procedure involving only three precipitations shown to be frequently insufficient remove completely 1.c. polymer. Using 8 10 and monitoring &lt;0,1 wt.‐%, resultant polymers have found both higher glass transition temperatures clearing temperatures; more consistent phase are also obtained batch batch.

Abstract In this structure–property correlation study we have investigated a number of novel disc-shaped compounds incorporating 1,3,5-trisubstituted benzene at the central core. All materials with peripheral arms attached through an ester linkage exhibited columnar phase (Colr or Colh). The sole use core–OOC–arm linkages resulted in Colr phase, whereas any inclusion core–COO–arm caused Colh phase. We suggest that mesophases are being generated due to space occupied regions by gradual offset...

Abstract The preparation of several 4'-alkylphenylethyl- and trans-4'-alkylcyclohexyl-ethyl-4,4'-disubstituted biphenyls their 2-fiuoro derivatives is described transition temperatures are reported. effect on the caused by replacement a cyclohexane ring benzene fluoro-substitution nematic, smectic A B thermal stabilities discussed. In these systems, in others, when lateral fluoro-substituent points towards longer terminal aliphatic unit (alkyl or alkylcyclo-hexylethyl) it causes greater...

Abstract A large number of ferroelectric dopants incorporating a chiral lactate unit, , have been synthesized and extrapolated values Ps as high 160 nC cm−2 found, although many these compounds did not show any liquid crystal behavior. Terphenyls laterally fluoro-substituted terphenyls the unit also synthesized, in one case, host material with an SC * phase value 124 was obtained. Compounds containing two units (one which unit) were either directly linked or separated by phenyl ring; latter...