Ranganathan Shashidhar

Polestar Technologies · Research

The electro-optical and structural properties of chiral lactic acid derivatives with keto linkage group ((S)-4-((1-alkoxy-1-oxopropan-2-yloxy) carbonyl)phenyl4’-alkyloylbiphenyl-4-carboxylates denoted as KL n/m) exhibiting Sm C* phase and Sm A*−Sm C* phase transition have been studied by using a thermodynamic model based on Landau-de-Gennes theory....

Pseudo binary oxide thin films,(TiO2)1-x-(Al2O3)x, were prepared by spray pyrolysis technique on cleaned quartz and silicon substrates. The prepared precursor solutions of Al2O3 and TiO2 were mixed thoroughly in appropriate volume, calculated from the molar fraction. The XRD pattern of Al2O3-TiO2 film shows anatase phase and mixed phase of Al2TiO5...

The nano porous surface structured TiO2 and Al2O3-TiO2 thin films were prepared using spray pyrolysis technique at 350°C. The XRD pattern of Al2O3-TiO2 film shows anatase phase and mixed phase of Al2TiO5. The surface morphology of films show a uniformly distributed nano porous structure. The elemental analysis through EDAX shows good stoichiometry....

The TiO2 films were deposited using Spray Pyrolysis Technique at 300 °C. The as deposited TiO2 films were annealed isochronally at temperatures of 400 °C, 500 °C and 600 °C under air ambient at constant time duration of 30 minutes. The surface morphology show a uniform distribution of TiO2 nano particles having spherical shape grain and estimated v...

Copper oxide (CuO) thin films were deposited on Si (100) substrates at 300 °C by spray pyrolysis technique under optimum conditions. The structural, morphological and compositional studies of the films were made through XRD, Raman, Photoluminescence (PL), SEM and EDAX techniques. XRD and SEM studies reveal that the as prepared films possess monocli...

Titanium dioxide (TiO2) thin films with different thicknesses (55–95nm) were deposited in a multi-cycle on Si (100) substrates at a temperature of 350°C by spray pyrolysis technique under optimum conditions, for the application as a window layer for hetero-junction solar cells. The dark-light I-V characteristics of Au/TiO2/p-Si/Al hetero-junction s...

Titanium oxide films were prepared on ITO coated glass substrates at 350 C using titanium (IV) isopropoxide, acetylacetonate and absolute ethanol as precursors by spray pyrolysis technique. The prepared films were characterized by X-ray diffraction, Scanning electron microscope, Fourier transform infrared spectroscopy and Energy dispersive analysis...

The effect of pressure on several mesogens which possess a strongly polar terminal group (CN or NO2) is studied. In all cases the partially bilayer smectic A (Ad) gets bounded while the nematic phase gets more stabilised at high pressures. In the case of reentrant nematogens, the maximum pressure of smectic stability is seen to be related to the te...

A non-invasive, calorimetric infection detector is provided, comprised of a substrate, and one or more indicator compositions disposed upon or incorporated therein. These indicator compositions exhibit a persistent change color when exposed to gaseous oxides of nitrogen and acids formed therefrom, providing a means of detecting NO production in a w...

Titanium oxide thin films were prepared using solutions of titanium (IV) isopropoxide, acetyl acetonate dissolved in various alcoholic solvents such as methanol, absolute ethanol, 1-butanol, 2-butanol, 1-propanol, 2-propanol and t-butanol in the volumetric ratio's of 1:1.5:22.5 by spray pyrolysis technique at substrate temperature of 350 º C under...

Integrated Child Development Services (ICDS) programme continues to be the world’s most unique early childhood development programme, which is being satisfactorily operated since three decades of its existence. The programme provides package of services, comprising supplementary nutrition, immunisation, health check-up, referral services to childre...

Health is an essential requirement of every individual and so much so of national and international society. It is an important input in the developmental process. The status of under-nutrition and malnutrition in women and children, by direct intervention (Provision of supplementary nutrition) is not likely to improve unless the dietary practices...

Honey has a potent broad-spectrum antibacterial action that may make it suitable for "anti-infective" treatment of periodontal disease. The aims of this study are as follows: 1) to evaluate the antibacterial efficacy of honey against oral bacteria and compare the same with 0.2% chlorhexidine; and 2) to compare antiplaque efficacy in vivo with chlor...

We report here the results of detailed density, dielectric and x-ray studies on three systems exhibiting different types of Smectic A-Smectic A transitions. It is found that although the layer spacing shows marked changes at the transitions, the corresponding density changes are extremely small. In every case studied, the dielectric anisotropy show...

The field dependent birefringence and the tilt angle are measured for a series of four electroclinic liquid crystals. The zero-field birefringence decreased significantly and monotonically with the length of the siloxane side chain. For all four samples, the birefringence and the electroclinic tilt angle increased substantially with the application...

The electro-optical properties of an electroclinic liquid crystal have been investigated using a spatially resolved technique which measures the birefringence, optical tilt angle and extinction within adjacent stripe domains. A comparison of these results with the data obtained from standard optical and X-ray measurements suggests the presence of s...

The thickness dependence of ferroelectric polarization in a SmC* liquid crystal exhibiting a large value of polarization has been investigated. It is observed that the saturation value of the polarization shows no significant thickness dependence. This observation is in accordance with a recent theoretical framework developed by Galerne. It is show...

Novel liquid crystalline Low Molecular Mass (LMM) materials bearing two chiral lactate groups, as well as compounds of like structure to MHPOBC have been synthesized. All the LMM compounds exhibit the SmC*A (antiferroelectric) and/or SmC*gamma (ferrielectric) phases. The mesogens have been incorporated as pendant groups on polymer backbones of thre...

The implementation of circuit architectures based on molecular electronic devices has been impeded by the availability of facile fabrication schemes for the interconnection of individ-ual devices. The deposition and patterning of a top contact layer between adjoining devices for interconnection purposes can re-sult in contacts of poor fidelity, whi...

X-ray, electrical, electro-optical, and dielectric studies in the de Vries smectic A (SmA) phase of organosiloxane derivatives exhibit features surprisingly different from that of a conventional SmA phase. The switching data show a double peak profile, characteristic of an antiferroelectric (AF) structure. A model with the adjacent smectic layers h...

A quantitative study of the structure and correlation of individual layer interfaces in a liquid-crystalline polymer multilayer film is reported. Off-specular and specular X-ray scattering data on successively deposited Langmuir-Blodgett films of the polymer show that the roughness of the first and subsequently deposited smectic layers is directly...

The theory of melting of molecular crystals developed by Pople and Karasz, which takes into account order-disorder processes in both the positions and orientations of the molecules, is discussed in a slightly modified form. The theory is an extension of the two-lattice model of Lennard-Jones and Devonshire so as to allow the molecules to take up tw...

The modified form of the Pople-Karasz theory of melting of inolecualr crystatls in a pervious paper is applied to study the thermodynamics of solid-solid and melting trasitions. The results are in substantial agreement with the predictions of the theory in its original form.

IntroductionDevelopment of Materials with Large Electroclinic Coefficients (ECE)Layer Buckling and Associated EffectsOther Symmetry-Breaking EffectsApplication of Electroclinic Liquid Crystals

The study of charge transport through increasingly complex small molecules will benefit from a detailed understanding of how contaminants from the environment affect molecular conduction. This should provide a clearer picture of the electronic characteristics of molecules by eliminating interference from adsorbed species. Here we use magnetically a...

The correlation between molecular structure and electrooptic performance is studied for novel room temperature chiral smectic A liquid crystals. It is observed that slight modifications of the hydrocarbon chain connected to the chiral center result in dramatic differences in their electrooptic performance. If the hydrocarbon chain is shortened or i...

An electro‐optical technique was used to measure the rotational viscosity of nematic liquid crystals, whose structures were chosen to investigate the effects of linking groups and lateral groups on rotational viscosity. These results are compared with the theory developed by Osipov and Terentjev. It is shown that the theory is useful in predicting...

Various research groups, including ours, have observed switching with memory behavior at room temperature from a monolayer of oligo(phenylene ethynylene) (OPE) molecules with a nitro sidegroup.^1,2. This switching behavior has the potential to be used in molecular electronic devices. However, the transport mechanisms of this ``nitro'' molecule are...

Self-assembled monolayers (SAMs) of the isocyano derivative of 4,4'-di(phenylene-ethynylene)benzene (1), a member of the "OPE" family of "molecular wires" of current interest in molecular electronics, have been prepared on smooth, {111} textured films of Au and Pd. For assembly in oxygen-free environments with freshly deposited metal surfaces, infr...

Reported herein are the synthesis, electrochemical and structural characterization of wire-like Ru2-alkynyl compounds, Ru2(ap)4(Ln)x, where ap is 2-anilinopyridinate, and Ln is –(CCC6H4)nSCH2CH2SiMe3 with n=1 (1) and 2 (2), and x can be 1 (a) and 2 (b). Reactions between Ru2(ap)4Cl and one equiv. of LiLn yielded the mono-alkynyl compound only, whil...

Reported in this contribution are the synthesis, characterization, and charge transport properties of wire-like Ru2(ap)4(OPEn), where ap is 2-anilinopyridinate and OPE is -(CCC6H4)nSCH2CH2SiMe3 with n = 1 (1) and 2 (2). Scanning tunneling microscopy (STM) measurements of compound 2 inserted into a SAM of C11 thiol reveal that molecule 2 exhibits (i...

A three-dimensional bottom-up self-assembly technique is developed to use biomolecules such as DNA as scaffolds. The use of viruses as nanoscale scaffolds for devices provide the exquisite control of positioning on the nanoscale. The efficacy of the approach is tested on 3D conductive molecular networks using cowpea mosaic virus (CPMV) as a scaffol...

The second- and fourth-order apparent orientational order parameters of the core part of the molecule P2 (app) and P4 (app) , have been measured by polarized vibrational Raman spectroscopy for a homogeneously aligned ferroelectric smectic liquid crystal with three dimethyl siloxane groups in the achiral terminal chain, which shows de Vries-type phe...

Molecular electronics has been proposed as a pathway for high-density nanoelectronic devices. This pathway involves the development of a molecular memory device based on reversible switching of a molecule between two conducting states in response to a trigger, such as an applied voltage. Here we demonstrate that voltage-triggered switching is indee...

We have studied the alignment of nematic liquid crystals on photo-sensitive chemisorbed monolayers. Surface modification and a single UV exposure at normal incidence resulted in photo-dimerized monolayers. A uniform, planar alignment of liquid crystals is realized on these surfaces. Chemical modification of the photo-sensitive chromophores of the m...

The scaling of conductance across metal−molecule−metal junctions consisting of self-assembled monolayers of dithiol molecular wire candidates is demonstrated through current−voltage measurements carried out by two experimental techniques. We show that scanning tunneling microscopy measurements on single molecules are correlated with crossed-wire me...

Coupling of photosynthetic reaction centers (RCs) with inorganic surfaces is attractive for the identification of the mechanisms of interprotein electron transfer (ET) and for possible applications in construction of photo- and chemosensors. Here we show that RCs from Rhodobacter sphaeroides can be immobilized on gold surfaces with the RC primary d...

The issue of state change of a poly(3,4-ethylenedioxythiophene) (PEDOT) derivative from an insulating to a conducting one, was discussed. The change was made possible by the cleavage of a moderate length electron withdrawing side-group to reveal the highly conducting methanol derivative P(OH-EDOT). Fourier transform infrared (FTIR) spectroscopy and...

A detailed investigation of the processing parameters influencing the oxidative polymerization of 3,4-ethylenedioxythiophene (EDOT) and a methanol-substituted derivative (EDOT–CH2OH) was performed with the goal of maximizing the conductivity of the polymer. We show that the conductivity can be significantly enhanced by varying the monomer, oxidant...

We demonstrate the ability to tune the current rectification in metal–molecule–metal junctions through control of the interaction strength of one of the two metal–molecule contacts. Current–voltage characteristics of thiolate bound molecular wires with a nitro or pyridine termination show that the extent of current rectification in a molecular junc...

The fabrication of carbon nanotube (CNT) devices using a new parallel assembly technique that control CNT placement using arrays of micromagnetic traps (MMT) was discussed. The method to control CNT placement on surfaces includes directed chemical vapor deposition (CVD) growth of carbon nanotubes, electrophoretic trapping and selective deposition o...

The addition of small, hydroxylated secondary dopants (SDs) can greatly decrease the surface resistance (SR) of poly(3,4-ethylenedioxythiophene)–poly(styrenesulfonate) (PEDOT–PSS) thin films with virtually no loss in film transparency. For example when 2,2′-thiodiethanol or glycerol are added to an aqueous suspension of PEDOT–PSS, thin films cast f...

We report low-temperature charge transport measurements of metal−molecule−metal junctions. Studies on insulating alkyl and π-conjugated molecular wires provide experimental insight into the coupling between tunnel charge carriers and molecular vibrations in molecular electronic systems. By comparison with other vibrational spectroscopy studies and...

The reaction between Os-2(OAc)(4)Cl-2 and Hap (Hap is 2-anilinopyridine) under prolonged refluxing conditions resulted in a new Os-2(III) compound, Os-2(ap)(4)Cl-2 (1). The molecular structure of 1 was determined from a single crystal X-ray diffraction study, which revealed an Os-Os bond length of 2.396[1] Angstrom, and a cis-(2,2) arrangement of t...

When an ultrasonic wave is applied to a nematic liquid-crystal cell, the molecules change their orientation, leading to a change in the optical intensity transmitted through the cell. Modeling this acousto-optic effect involves three separate theoretical issues: (a) calculating the intensity of sound transmitted through the cell walls into the liqu...

Nanowire metal−molecule−metal junctions containing dithoilated molecules of dodecane (C12), oligo(phenylene ethynylene) (OPE), and oligo(phenylene vinylene) (OPV) were prepared by replicating the pores of sub-40 nm diameter polycarbonate track etched membranes. Bottom Au−S or Pd−S contacts were made by potential-assisted molecule assembly onto the...

We present a demonstration of molecular rectification in a metal−molecule−metal junction created by self-assembly where endgroup chemistry does not influence the observed conductance asymmetry. Using a protection scheme which allows for stepwise deprotection of aryl thiols, the deposition of α,ω-dithio-molecules with a preferred polar order can be...

The dependence of the acousto-optic response of two nematic liquid crystals on several possible future device parameters is investigated. Several paths for possible optimization are identified. A large enhancement of the acousto-optic response is obtained through optimization of the incident angle of the acoustic wave. The power required for a give...

Polar interactions between liquid crystal molecules and cell surfaces give rise to the surface electroclinic effect. This results in rotation of the layer normal away from the alignment direction near the surface and an interfacial region where the molecular director twists from the alignment direction until it reaches the layer normal direction. W...

A method of fabrication of twisted nematic device is described utilizing the monomolecular chemisorbed layer on at least one internal transparent electrode of capillary cell. The layer is capable of aligning and re-aligning the liquid crystal molecules upon UV irradiation. The preliminary uniform LC orientation with high contrast of the order of 10...

For molecular electronics to become a viable technology the factors that control charge transport across a metal-molecule-metal junction need to be elucidated. We use an experimentally simple crossed-wire tunnel junction to interrogate how factors such as metal-molecule coupling, molecular structure, and the choice of metal electrode influence the...

In bulk ferroelectric liquid crystals, the molecular director twists in a helix. In narrow cells, this helix can be unwound by an applied electric field or by boundary effects. To describe helix unwinding as a function of both electric field and boundary effects, we develop a mesoscale simulation model based on a continuum free energy discretized o...

A study was conducted on three materials showin the de Vries type of SmA* phases using the electro-optic and FTIR techniques. A comparison of the experimental results with Monte Carlo simulations and some theoretical findings lead a second-order SmA-SmC* transition possesses a structure with no long-range correlation within the smectic layer given...

Charge transport across a metal−molecule−metal junction consisting of π-conjugated molecular wires in a densely packed monolayer is studied as a function of junction area. The current−voltage characteristics, measured using a crossed-wire junction at different contact forces, scale onto a single curve. The integer scaling factors, ranging from 1 to...

Current–voltage characteristics as measured by scanning tunneling microscopy for several different molecular backbones are presented. It is demonstrated that isolated oligo(phenylene ethynylene) molecules have the same measured conductance as oligo(phenylene ethynylene) molecules in a crystalline self-assembled monolayer. This result suggests that...

A new series of laterally substituted bis(alkoxybenzoyloxy)hydroquinone compounds has been synthesized and their mesomorphic properties studied. A number of hydroquinone compounds were synthesized with terminal n-alkoxy chains ranging from n-butyloxy to n-decyloxy. Additionally, lateral substituents ranging from n-butyl to n-octyl were incorporated...

To investigate the electrical characteristics of organometallic complexes as molecular conductors, organometallic pi-conjugated molecules of the type trans-[PtL2(CCC6H4SAc-4)2], where L = PCy3, PBu3, PPh3, P(OEt)3, P(OPh)3, were synthesized and characterized by NMR, IR, UV, and X-ray spectroscopies. For the three complexes (L = PCy3, PPh3, and P(OE...

Biological cells have been imaged using liquid crystals as an optical amplification medium. Preferential orientation of the liquid-crystal molecules at the surfaces of cells immobilized on substrates leads to well-resolved images, with very sharp contrast compared to images observed by standard phase-contrast microscopy. The feasibility of this tec...

Measurements of the orientational order parameter of dissolved dichroic dyes are reported for two smectic-A liquid crystals that tilt in the presence of an in-plane electric field without any decrease in the layer spacing. The dye order parameter is determined by measuring the anisotropic absorption of linearly polarized light. Different dyes are u...

In a nematic liquid-crystal cell, the molecules can be realigned by an ultrasonic wave, leading to a change in the optical transmission through the cell. We present a model for this acousto-optic effect, and show that the magnitude of this effect is controlled by a director-density coupling. We then measure the optical transmission as a function of...

Novel ferroelectric liquid crystal materials with large pyroelectric coefficients (exceeding 100 nC/cm2·K even under zero applied bias field) as compared to those reported so far have been synthesized. The materials described show a low melting point (<−10 °C) and low SmC*−SmA phase transition temperatures suitable for practical devices. Combined w...

Current-voltage (I-V) characteristics for metal-molecule-metal junctions formed from three classes of molecules measured with a simple crossed-wire molecular electronics test-bed are reported. Junction conductance as a function of molecular structure is consistent with I-V characteristics calculated from extended Hückel theory coupled with a Green'...

Charge transport studies across molecular length scales under symmetric and asymmetric metal-molecule contact conditions using a simple crossed-wire tunnel junction technique are presented. It is demonstrated that oligo(phenylene ethynylene), a conjugated organic molecule, acts like a molecular wire under symmetric contact conditions, but exhibits...

The demand for displays with a large number of pixels is being driven by both military and commercial applications. Displays with very high information content are expected to have >1Gigapixels, requiring I/O bandwidth well beyond current integrated circuit technology, if display architectures continue as they have in the past. In this paper we pre...

Films fabricated from commercially available poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) aqueous dispersions have been widely used in many electronic and optoelectronic applications. Previous attempts to utilize them as anodes in organic light-emitting diodes (OLEDs) were not satisfactory due to their low conductivity. In th...

The ionic conductivity of ferroelectric liquid crystals used for pyroelectric detection is a measure of the noise contribution to the output of the device. This is obtained from a measurement of the dielectric loss of the liquid crystal material. An annealing procedure has been developed that reduces the ionic conductivity and hence the dielectric...

A detailed study of the dependence of the polar anchoring energy of liquid crystals on the chemical structure of photoaligning layers is presented. The monolayer alignment layers consist of different chemical groups at the terminus so that the interaction of the alignment layer with the liquid-crystal molecules is systematically varied. The results...

Activity in the field of molecular electronics is steadily increasing, and the race is on to develop molecules that exhibit useful device properties. As important as molecular "devices" will be, advances in molecular electronics will not be made unless we also have the molecular parts interconnect devices with each other and the outside world, i.e....

The thickness of a ferroelectric liquid crystal cell strongly affects its polarization response under an applied electric field, particularly when the thickness is of the same order as the chiral pitch length, e.g. microns. To understand this size effect, we study a mesoscale simulation model based on a continuum free energy functional discretized...

Poly(ethylenedioxythiphene) (PEDOT) is a promising candidate for an optically transparent organic conductor. We have used x-ray diffraction to characterize mixtures of PEDOT with a variety of ionic and nonionic dopants. We establish correlations between the local structural order and the transport properties.

We report a photoemission study of the interfaces between spin-cast films of a new variation of a polymer blend consisting of poly(3,4-ethylenedioxy-thiophene) (PEDOT) and poly(4-styrenesulfonate) (PSS) and glycerol as an additive, and vacuum-evaporated hole transport layers (HTL) of 4,4'-bis(carbazol-9-yl)biphenyl (CBP),N,N'-diphenyl-N,N'-bis(1-na...

Poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) aqueous dispersion (PEDOT:PSS) is a highly conductive polymer. Attempts to utilize them as an anode in an organic light emitting diode have been made but a satisfactory result was not obtained due to low device efficiency caused by the relatively high surface resistance and poor optical transp...

An unresolved issue in the theory of liquid crystals is the molecular basis of the electroclinic effect in the smectic-A phase. Recent x-ray scattering experiments suggest that, in a class of siloxane-containing liquid crystals, an electric field changes a state of disordered molecular tilt in random directions into a state of ordered tilt in one d...

The noise level in a pyroelectric device and therefore the sensitivity is dictated mainly by the dielectric losses in pyroelectric materials. An annealing procedure has been developed that reduces the dielectric loss significantly. The procedure consists of subjecting the ferroelectric liquid crystal sample to an electric field in the isotropic pha...

We report a synthesis of 7-(8-trimethoxysilyloctyloxy)coumarin that can self-assemble into optically active monolayers on substrates. Atomic force microscopy and UV–vis spectroscopy have been used to characterize the self-assembly processes and photochemical reaction of the coumarin silane on substrates. We also show that when irradiated with linea...

We present here results of our studies on the structure-property relationship of side chain liquid crystalline polymers exhibiting ferroelectric behavior. In particular the polarization properties of linear as well as cyclic siloxane-based ferroelectric polymers and the nature of the self-assembly of linear siloxane-based systems in monolayers and...

Display research has comprised a substantial portion of the defense investment in new technology for national security for the past 13 years. These investments have been made by the separate service departments and, especially, via several Defense Advanced Research Projects Agency (DARPA) programs, known collectively as the High Definition Systems...

We have investigated the effect of surface order on the orientation and mobility of pentacene. The surface order was created using monolayers and polymers that are normally used to align liquid crystals. Rubbed polyvinylalcohol layers were found to align approximately 27% of the pentacene grains within a 30 degrees range. When introduced in a thin-...

A photoemission study of the interface between spin-cast films of a conducting polymer blend consisting of poly(3,4-ethylenedioxythiophene) (PEDOT), poly(4-styrenesulfonate) (PSS) and glycerol as an additive, and vacuum-evaporated hole transport layers (HTL) of 4,4′-bis(carbazol-9-yl)biphenyl, N,N′-diphenyl-N,N′-bis(1-naphthyl)-1-1′biphenyl-4,4′-di...

We carry out Monte Carlo simulations to investigate the effect of molecular shape on liquid-crystal order. In our approach, each model mesogen consists of several soft spheres bonded rigidly together. The arrangement of the spheres may be straight (to represent uniaxial molecules), Z-shaped (for biaxial molecules), or banana-shaped (for bent-core m...

Two outstanding theoretical questions on chiral smectic-A liquid crystals are: What is the distribution of molecular orientations, and how does the distribution change when an applied electric field induces an electroclinic tilt? In some liquid crystals, an electric field makes the molecules tilt as rigid rods from an initially untilted state to a...

The design of a high-pressure cell which uses DTA as a probe to detect weak first-order transitions is described. Experimental data are presented to illustrate the applicability of this technique to the study of phase transitions in liquid crystalline materials under pressure.

Evidence of photodimerization-induced positional order in self-assembled monolayers (SAMs) is reported. Scanning force microscopy studies of SAMs of an alkylsilane with an olefinic group on a silicon surface show that the terminal alkyl chains are initially disordered but become highly ordered upon irradiation with UV light. Development of the crys...

Synthesis of a new class of triethoxysilane materials for photoinduced orientation of liquid crystals is reported. A feature of these silanes is the incorporation of a photosensitive chromophore in the chemical structure. This leads to the formation of a complete monolayer with smooth surface morphology. The effect of varying the chemical structure...

Smectic-A liquid crystals exhibiting a large electroclinic effect are important for applications in view of their analog gray scale capability. In most of these materials, large electroclinic tilt angles are accompanied by buckling effects due to layer compression. This layer buckling is easily observed in an optical microscope as periodic stripes...

We have carried out X-ray reflectivity as well as X-ray diffuse scattering studies on thin liquid crystalline polymers formed on solid surfaces. Due to the microphase separation of the siloxane backbone from the mesogenic end group, the polymer films form extremely ordered layers in which the thermal fluctuations are highly quenched. This enables u...

Chiral twisting of the molecular orientation within the layer of a smectic-A liquid crystal has been investigated using circular dichroism spectroscopy. The results indicate that a rotation of the layers away from the alignment direction is induced by the surface electroclinic effect. This leads to an interfacial region where the molecular director...

Optical and x-ray scattering studies of a chiral, organosiloxane smectic-A liquid crystal indicate a large field induced optical tilt of up to 31 degrees accompanied by a very small contraction of the smectic layers. This result suggests that the molecules have a nonzero tilt even with no applied field, and that the primary effect of the field is t...

Nematic liquid crystals are easily aligned by rubbing of the confining cell walls, but the mechanism for the alignment is not well understood. The nematic director is sometimes, but not always, lined up with the rubbing direction. We investigate this effect via molecular-scale Monte Carlo simulations, with a system of 5,000 rigid rod-like particles...

Using Monte Carlo simulation methods, we explore the role of molecular shape in the phase behavior of liquid crystals and the electroclinic effect. We study a "bent-rod" mesogen shaped like the letter Z, composed of seven soft spheres bonded rigidly together with no intramolecular degrees of freedom. For strongly angled molecules, we find that ster...

Chiral smectic A electroclinic liquid crystalline materials are prime candidates for electrooptic applications because of their gray scale capability and fast dynamic response. The evolution of this technology greatly depends on the development of chiral smectic A materials with large induced tilt angles, field-independent fast switching times and...