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The effect of acid concentration on the conversion between three distinct optical species, spiropyran (SP), merocyanine (MC) and MC-[OH.sup.+], are examined through spectrophotometric and NMR studies. The study shows that the acidochromic rate of conversion between SP and MC-[OH.sup.+] is inversely proportional to the concentration of acid present in the media.

The atropisomeric dopant 2,2',6,6'-tetramethyl-3,3'-dinitro-4,4'-bis[4-nonyloxybenzoyl)oxy]biphenyl (1) induces a ferroelectric SmC* phase when doped into the SmC liquid crystal hosts2-(4-butyloxyphenyl)-5-octyloxypyrimidine (PhP1) and (plusmn)-4-[(4-methylhexyl)oxyl]phenyl 4-decyloxybenzoate (PhB). The results obtained using the atropisomeric dopant as probe suggest that the chiral perturbation exerted by 2,2',6,6'-tetramethyl-3,3'-dinitro-4,4'-bis[4-nonyloxybenzoyl)oxy]biphenyl can amplify the polarization power of another atropisomeric dopant.

Thermal racemization is examined with reference to a series of six substituted indolinobenzospiropyrans. The results of this study which show competition between the polar and nonpolar mechanisms are presented.

A study synthesized in optically pure form 11 chiral, atropisomeric dopants and measured their polarization power in five sC liquid crystal hosts representing four distinct structural classes of mesogens. It is argued that polarization amplification occurs through a feedback mechanism where intercore chirality transfer leads to an asymmetric distortion of the ferroelectric sC lattice. This in turn further increases the conformational asymmetry of the atropisomeric dopant.

Research was conducted to examine the role of dispersion and electrostatic forces on solute-solvent interactions in a nematic liquid crystal phase. A series of 23 substituted biphenyl, phenylpyridine and bipyridine derivatives were doped in the nematic liquid crystal host. Results indicated that charge-transfer complexation and molecular dipole-dipole interactions do not have a significant effect on the stability of arene-arene interactions in the nematic phase.

A novel chiral dopant is synthesized in 11 steps from 4,4'-dihydroxy-2,2'-dimethyl-6,6'-dinitrobiphenyl to give 9% yield. It induces a ferroelectric Sc* phase in two Sc liquid crystal hosts via spontaneous polarization. It induces positive polarization in the presence of cyclohexanecarbonitriles and negative polarization in the presence of phenyl benzoate. The polarization power of the dopant is dependent on the nature of the Sc host.

A molecular orbital computational study was carried out on cis-1,3-diarylcyclohexanes to quantify pi-stacking of the aromatic rings from the corformational equilibria shifts. The calculations from Hammett correlations, electrostatic potentials, and molecular orbital energy gaps conformed with experimental results. Arene-arene pi-stacking is governed more by electrostatic than charge-transfer interactions. The closest correlation is detected on the pi-face of individual component arenes by electrostatic potentials measured from the electron density surface.

The synthesis of axially chiral (arylmethylene)cycloalkenes in their racemic and enantiomeric forms leads to a study of their use in optical switches. Theirirradiation with UV light leads to double-bond isomerization and to racemization, but sometimes to destruction of both enantiomers. The use of the chiral exciton coupling model allows these monochromophoric compounds to exhibit enough anisotropy induce cholesteric behavior upon addition to nematic crystals. Other results of this evaluation and their implications are discussed.

The article explains the design, synthesis and characterization of two different series of liquid crystals with 'de Vries-like' properties. The frustration observed between the elements promoting SmA and SmC phases is also discussed.

A new approach is described where in the axially chiral monomers are employed for the synthesis of the chiral periodic mesoporous organosilicates. These materials are shown to be widely used in various applications, including the catalysis and separation science.

Various routes are examined for the synthesis of chiral biphenyl species that are substituted at the 2,2', 4,4' and 6,6' positions. An Ullmann coupling is employed on a dibrominated arene, which has occurred selectively at the more hindered bromine by virtue of the directing effect of an ortho ester substituent.

The axially chiral dopants (R)-5,5'-5,6'- and 6,6'-diheptyloxy-2,2'-spirobiindan-1,2'-dione were synthesized in optically pure form, and their absolute configurations were assigned by the exciton chirality method using circular dichroism spectroscopy. The new compounds were doped in four achiral liquid crystal hosts to give chiral smectic C* phases with spontaneous polarizations that vary with the core structure of the host.

The synthesis and characterization of smectic C* (SmC*) mesogens with a chiral fluorenol core as the only stereopolar unit are undertaken. The role of chiral smectic C* (SmC*) liquid crystals in the commercial development of high-resolution reflective microdisplays is discussed.

The ferroelectric SmC* phase is a chiral liquid crystal phase characterized by a spontaneous electric polarization (Ps), which can be coupled to an electric field to produce an electrooptical light shutter. In a ferroelectric SmC* host, the trans-cis photoisomerization of an achiral azobenzene dopant destabilizes the SmC* phase, which results in a decrease of polarization at constant temperature.

First example of a photochemically bistable FLC photoswitch using a photochromic dithienylethene dopant is presented. The spontaneous polarization of a ferroelectric liquid crystal can be modulated reversibly via photoisomerization of the dithienylethene dopant.

The (R,R)-6,6'-bis(1-methylheptyloxy)-5,5'-dinitrothioindigo was synthesized based on photoirradiation techniques and analyzed to characterize the kinetics of spontaneous polarization. The complex compound was composed of chiral side chains that were strongly coupled with the thioindigo core via steric and dipole-dipole coupling with the adjacent nitro groups. The spontaneous polarization of the ferroelectric liquid crystal was also enhanced without the concomittant destabilization of the chiral smectic phase.

Molecular structure and helicity of induced chiral nematics were investigated with regard to chiral biphenyls and short-range and electrostatic-induction interactions.

The axially chiral dopants (R)-5,5'-, 5,6'-, and 6,6'-diheptyloxy-2,2'-spirobiindan-1,1'-dione ((R)-2, -3, and -4) were synthesized in optically pure form, and their absolute configurations were assigned by the exciton chirality method using circular dichroism spectroscopy. These new compounds were doped in four achiral liquid crystal hosts to give chiral smectic C* (SmC*) phases with spontaneous polarizations (Ps) that vary with the core structure of the host. The spontaneous polarization induced by the 5,5'-dialkoxy derivative (R)-2 is uniformly positive, whereas that induced by the 6,6'-dialkoxy derivative (R)-4 is uniformly negative and shows a different trend in host dependence. Polarization power (δp) values range from +21 nC/cm² for (R)-2 in 2',3'-difluoro-4-heptyl-4"-nonyl-p-terphenyl (DFT) to -1037 nC/cm² for (R)-4 in 4-(4'-heptyl[1,1'-biphen]-4-yl)-1-hexylcyclohexanecarbonitrile (NCB76). The unsymmetrical dopant (R)-3 behaves like a hybrid of the two symmetrical isomers, with lower absolute values of δp, on average, and varying signs of Ps. ²H NMR spectra of the doped mixtures using racemic mixtures of 2-4 with OCD2C6H13 side-chains, in combination with phase diagrams, show that relatively minor changes in the dopant structure, that is, moving the alkoxy side-chains from the 5,5' to the 6,6' positions of the spirobiindandione core, have profound effects on dopant-host compatibility, and on the propensity of the dopant to exert chiral perturbations in the host environment. The variations in sign and magnitude of δp as a function of alkoxy group positions are rationalized based on an analysis of zigzag conformations that conform to the binding site of the SmC host according to the Boulder model. [ABSTRACT FROM AUTHOR]

The article discusses the formation of ferroelectric liquid crystals (FLCs) with de Vries-like structure. It mentions that FLCs are usually made from achiral liquid crystal mixture and a chiral dopant. It describes the formation of de Vries-like materials which are a class of liquid crystals with layer contractions of less than or equal to one percent. An experiment to create ferroelectric liquid crystals (FLCs) with de Vries-like structure is described.