Electronic Structure Properties in the Nematic Phases of FeSe

We investigate the electronic structures of FeSe in the presence of different possible orders and spin-orbit coupling （SOC）. It is found that only the ferro-orbital order （FO） and the collinear antiferro-magnetism （C-AFM） can simultaneously induce splittings at F and M. Bicollinear antiferro-magnetism （B-AFM） and SOC have very similar band structures on F-M near the Fermi level. The temperature T insensitive splitting at F and the T-dependent splitting at M observed in recent experiments can be explained by the d-wave bond nematic （dBN） order together with SOC. The recent observed Dirac cones and their T-dependence in FeSe thin films can also be well explained by the dBN order together with the band renormMization. Their thickness- and cobalt-doping- dependent behaviors are the consequences of electron doping and reduction of Se height. All these suggest that the nematic order in the FeSe system is the dBN order.

Mesomorphic Characteristics of Induced Chiral Nematic Phase of[Smectic LCP,PS(4BC/DM)/Nematic LC,E7/Chiral Dopant,CB-15]-Ternary Composite System

The phase transition behavior and aggregating states of [smectic LCP, PS(4BC/DM)/nematic LC, E7/chiral dopant, CB-15] ternary composite system were investigated on the basis of differential scanning calorimetry (DSC) measurement, polarizing optical microscopy (POM) observation and wide angle X-ray diffraction (WAXD) patterns. It was demonstrated that if the weight ratio of the chiral dopant was fixed as 4.8wt%, an induced chiral nematic (N^(*)) phase existed in the ternary system when PS(4BC/DM) ratio was below 47.6 wt%. Moreover, smectic like long range ordering appeared in the induced N^(*) phase in a certain temperature range just above the smectic A(S_(A))-N^(*) phase transition when PS(4BC/DM) ratio was between 19.1wt% and 47.6wt%.

Asymmetric dynamic phase holographic grating in nematic liquid crystal

A new scheme for recording a dynamic phase grating with an asymmetric profile in C60-doped homeotropically aligned nematic liquid crystal（NLC） was presented.An oblique incidence beam was used to record the thin asymmetric dynamic phase holographic grating.The diffraction efficiency we achieved is more than 40%,exceeding the theoretical limit for symmetric profile gratings.Both facts can be explained by assuming that a grating with an asymmetric saw-tooth profile is formed in the NLC.Finally,physical mechanism and mathematical model for characterizing the asymmetric phase holographic grating were presented,based on the photo-refractive-like（PR-like） effect.

Nematic and smectic stripe phases and stripe-Sk X transformations

Based on the findings of skyrmion nature of stripes and the metastability of a state of an arbitrary number of skyrmions,precisely controlled manipulation of stripes of skyrmion number 1 in pre-designed structures and mutual transformation between helical states and skyrmion crystals(Sk Xs)are demonstrated in chiral magnetic films.As a proof of the concept,we show how to use patterned magnetic fields and spin-transfer torques(STTs)to generate nematic and smectic stripe phases,as well as“UST”mosaic from three curved stripes.Cutting one stripe into many pieces and coalescing several skyrmions into one by various external fields are good ways to transform helical states and Sk Xs from each other.

MORPHOLOGY OF A THERMOTROPIC AROMATIC POLYESTER

The crystalline morphology of a thermotropic aromatic polyester has been studied by microscopy techniques. Spherulites with ringed structure under polarizing micioscope were observed for solution cast specimens, They were composed of radially growing crystalline lamellae of thickness around 100. It was found that the molecules were packed in the thickness direction. Banded texture was observed in randomly packed domains for melt cast specimens. The bands have the same width and internal structure as those usually observed in oriented specimens of these polymers obtained by shearing their mesomorphic melt.

Studies on Liquid Crystalline Bis[4-(p-phenoxy)-phenylbenzoate]Alkyldicarboxylat

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Polarizabilities and Orientational Order Parameter in N-(p-n-Ethoxybenzylidene)- p-n-Alkoxy Anilines, 2O.Om LC Compounds

n.m, n.Om, nO.m and nO.Om compounds play an important role in the fundamental and applied aspects. As a part of our systematic studies of the above homologous series regarding the synthesis, characterization and phase transition studies, here the authors report the polarizabilities and orientational order parameter, S in N-(p-n-ethoxybenzylidene)-p-n-alkoxy anilines, 2O.Om with m = 3 to 10 liquid crystalline compounds except with m = 5 which has been already published. The rest of the compounds exhibit the nematic LC phase except with m = 10 which shows the smectic-C phase along the nematic phase which is originally not detected by Godzwon et al. But the author’s observations with TM and differential scanning calorimeter have shown the existence on SmC phase in addition to nematic phase. Further, SmC is clarified using the histogram technique whose details are given below and are published elsewhere. The orientstonal order parameter, S is estimated using different methods and compared with the value obtained from birefringence, δn = (ne – no) where no field model is used. It is observed in these compounds case as in other LC compounds Vuks isotropic model is favored compared to that of anisotropic model proposed by Neugebauer.

Entanglement-free determination of pretilt angles of twisted nematic liquid-crystal cells by phase measurement

Because of low cost, fast response time, and high light transmittance, thin-film-transistor （TFT） driven twisted nematic （TN） liquid-crystal displays （LCDs） have been widely used in calculators, computer screens, and cell phones. The pretilt angle of the TN medium within the TFT-TN panel affects not only its response times and view- ing angles but also the light-leakage positions of fringed- field-induced disclination lines within pixels of theTFT-TN panel.

Tuning the helical twisting power of nematic liquid crystals induced by chiral 1,2-propanediol derivatives using varied substituents

In this study,a novel series of chiral 1,2-propanediol derivatives with different electron-donating and electron-withdrawing groups were synthesized and characterized by FT-IR and ~1H NMR.The helical twisting properties of all the chiral dopants were investigated by doping the chiral dopants into a nematic liquid crystal host（SLC-1717）.The results indicate that the donor-acceptor electron effect have a prominent influence on helical twisting property of the chiral nematic phase induced by the chiral dopants. Introducing electron-withdrawing groups into the terminal ends of chiral 1,2-propanediol can decrease the absolute values of the helical twisting power.In addition,the helix inversion temperatures of the induced chiral nematic phase are variational with the change of terminal groups.

Low and Wide Phase Transition Temperature Dimesogenic Compounds Consisting of a Cholesteryl and 4-（trans-4-n-Alkylcyclohexyl）phenoxy Mesogens

Unsymmetrical dimesogenic compounds with cholesteryl and 4-（trans-4-n-alkylcyclohexyl）phenoxy parts were synthesized by condensation of cholester-3-yl 6-bromohexanoate with appropriate 4-（trans-4-n-alkylcyclohexyl）- phenols. Structures and thermal phase behaviour of these dimesogenic compounds have been confirmed by IR, IH NMR, elemental analysis, DSC, polarity microscopy and XRD measurements. Their thermal phase behaviour was significantly different with that of other cholesterol-based dimesogens while they exhibited low and wide phase transition temperature.

The synthesis and phase transition of 4'-methylphenyl 4"-[(4-alkoxy-2,3,5,6-tetrafluorophenyl)ethynyl]benzoates

A homologous series of 4'-methylphenyl 4'-[(4-alkoxy-2,3,5,6-tetrafluorophenyl)ethynyl]-benzoates have been synthesized. Polarizing microscopic textural observation shows that such compounds exhibit enantiotropic nematic phase.

Liquid Crystalline Behaviours of the Complexes Based on 1,3,4-Oxadiazole Derivative and Benzoic Acid

A non-liquid crystal compound （4-POXD-6） containing the 1,3,4-oxadiazole group and pyridyl （py） group was synthesized. And a series of supramolecular mesogenic complexes were obtained by mixing 4-POXD-6 and 4-alkoxybenzoic acids （Cn, n=6, 8, 12）. The liquid crystalline properties of4-POXD-6/Cn （n=6, 8, 12） were in- vestigated by means of differential scanning calorimetry, polarized optical microscopy, and wide-angle X-ray dif- fraction. It was found that 4-POXD-6/Cn （6, 8） display monotropic nematic and smectic A phases, while 4-POXD-6/C12 exhibits a SmX phase in the heating process and a SmA phase in the cooling run. Vari- able-temperature FTIR spectroscopic studies revealed hydrogen bonds existed in both crystalline and liquid crystal- line phases.