scholarly journals Experimental and Computational Study of a Liquid Crystalline Dimesogen Exhibiting Nematic, Twist-Bend Nematic, Intercalated Smectic, and Soft Crystalline Mesophases

Molecules ◽  
2021 ◽  
Vol 26 (3) ◽  
pp. 532
Author(s):  
Emily E. Pocock ◽  
Richard J. Mandle ◽  
John W. Goodby
Keyword(s):  
Liquid Crystalline ◽  
Computational Study ◽  
Structure Property ◽  
Correlation Lengths ◽  
Aspect Ratios ◽  
Smectic Phases ◽  
Out Of Plane ◽  
Lower Temperature ◽  
Soft Crystal ◽  
Optical Textures

Liquid crystalline dimers and dimesogens have attracted significant attention due to their tendency to exhibit twist-bend modulated nematic (NTB) phases. While the features that give rise to NTB phase formation are now somewhat understood, a comparable structure–property relationship governing the formation of layered (smectic) phases from the NTB phase is absent. In this present work, we find that by selecting mesogenic units with differing polarities and aspect ratios and selecting an appropriately bent central spacer we obtain a material that exhibits both NTB and intercalated smectic phases. The higher temperature smectic phase is assigned as SmCA based on its optical textures and X-ray scattering patterns. A detailed study of the lower temperature smectic ‘’X’’ phase by optical microscopy and SAXS/WAXS demonstrates this phase to be smectic, with an in-plane orthorhombic or monoclinic packing and long (>100 nm) out of plane correlation lengths. This phase, which has been observed in a handful of materials to date, is a soft-crystal phase with an anticlinic layer organisation. We suggest that mismatching the polarities, conjugation and aspect ratios of mesogenic units is a useful method for generating smectic forming dimesogens.

Liquid Crystalline Compounds in the Thiophene Series, Part 11+ Liquid Crystalline Thiophene Carboxylic Esters

1995 ◽  
Vol 50 (8) ◽  
pp. 1265-1274 ◽  
Author(s):  
Gerhard Koßmehl ◽  
Barbara Hirsch
Keyword(s):  
Liquid Crystalline ◽  
Polarized Light ◽  
Scanning Calorimetry ◽  
Crystalline Phases ◽  
H Nmr ◽  
Smectic Phases ◽  
Liquid Crystalline Phases ◽  
Nematic Phases ◽  
Optical Textures ◽  
Carboxylic Esters

The new series of ten 4,4'-bis(5-alkyl-2-thienylcarbonyloxy)azobenzenes (2a -2j) and ten 2,5-bis(5-alkyl-2-thienylcarbonyloxy)toluenes (3a -3j) were prepared. These, as yet unknown esters were characterized in relation to their structures by elemental analyses, IR, UV, 1H NMR spectra and MS. The azobenzene-esters 2a -2j which form liquid crystalline phases were studied by microscopy under polarized light and DSC (differential scanning calorimetry). Through the observation of the optical textures nematic phases were monitored. Only 2j has an additional smectic phase; 2h and 2i form monotropic smectic phases during cooling. The toluene-esters 3a -3j do not form liquid crystalline phases.

Structure-property relations of liquid crystalline polymers

1987 ◽  
Vol 45 ◽  
pp. 460-463
Author(s):  
Linda C. Sawyer
Keyword(s):  
Solid State ◽  
Liquid Crystalline ◽  
Structural Model ◽  
Crystalline Polymer ◽  
Liquid Crystalline Polymers ◽  
Mechanical Anisotropy ◽  
Structure Property ◽  
Preparation Methods ◽  
Crystalline Polymers ◽  
Extended Chain

Recent liquid crystalline polymer (LCP) research has sought to define structure-property relationships of these complex new materials. The two major types of LCPs, thermotropic and lyotropic LCPs, both exhibit effects of process history on the microstructure frozen into the solid state. The high mechanical anisotropy of the molecules favors formation of complex structures. Microscopy has been used to develop an understanding of these microstructures and to describe them in a fundamental structural model. Preparation methods used include microtomy, etching, fracture and sonication for study by optical and electron microscopy techniques, which have been described for polymers. The model accounts for the macrostructures and microstructures observed in highly oriented fibers and films.Rod-like liquid crystalline polymers produce oriented materials because they have extended chain structures in the solid state. These polymers have found application as high modulus fibers and films with unique properties due to the formation of ordered solutions (lyotropic) or melts (thermotropic) which transform easily into highly oriented, extended chain structures in the solid state.

scholarly journals Computational study on the mechanism and kinetics for the reaction between HO2 and n-propyl peroxy radical

RSC Advances ◽  
2019 ◽  
Vol 9 (69) ◽  
pp. 40437-40444
Author(s):  
Zhenli Yang ◽  
Xiaoxiao Lin ◽  
Jiacheng Zhou ◽  
Mingfeng Hu ◽  
Yanbo Gai ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Temperature Regime ◽  
Computational Study ◽  
Peroxy Radical ◽  
Negative Temperature ◽  
Mechanism And Kinetics ◽  
Lower Temperature

The negative temperature dependence for the HO2 + n-C3H7O2 reaction in lower temperature regime.

Estimation of Seismic Energy Dissipation for Steel Slit Shear Walls Considering Out-of-Plane Buckling

2021 ◽  
Author(s):  
Yiming Ma ◽  
Liusheng He ◽  
Ming Li
Keyword(s):  
Energy Dissipation ◽  
Shear Walls ◽  
Seismic Energy ◽  
Thickness Ratio ◽  
Design Parameters ◽  
Test Results ◽  
Loading Test ◽  
Aspect Ratios ◽  
Out Of Plane ◽  
Energy Dissipation Capacity

Steel slit shear walls (SSSWs), made by cutting slits in steel plates, are increasingly adopted in seismic design of buildings for energy dissipation. This paper estimates the seismic energy dissipation capacity of SSSWs considering out-of-plane buckling. In the experimental study, three SSSW specimens were designed with different width-thickness ratios and aspect ratios and tested under quasi-static cyclic loading. Test results showed that the width-thickness ratio of the links dominated the occurrence of out-of-plane buckling, which produced pinching in the hysteresis and thus reduced the energy dissipation capacity. Out-of-plane buckling occurred earlier for the links with a larger width-thickness ratio, and vice versa. Refined finite element model was built for the SSSW specimens, and validated by the test results. The concept of average pinching parameter was proposed to quantify the degree of pinching in the hysteresis. Through the parametric analysis, an equation was derived to estimate the average pinching parameter of the SSSWs with different design parameters. A new method for estimating the energy dissipation of the SSSWs considering out-of-plane buckling was proposed, by which the predicted energy dissipation agreed well with the test results.

scholarly journals Multiresponsive polymeric microstructures with encoded predetermined and self-regulated deformability

2018 ◽  
Vol 115 (51) ◽  
pp. 12950-12955 ◽  
Author(s):  
Yuxing Yao ◽  
James T. Waters ◽  
Anna V. Shneidman ◽  
Jiaxi Cui ◽  
Xiaoguang Wang ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Transition Temperature ◽  
Energy Harvesting ◽  
Liquid Crystalline ◽  
Soft Robotics ◽  
Stimuli Responsive ◽  
Out Of Plane ◽  
Deformation Behaviors ◽  
Deformation Modes ◽  
Biological Organisms

Dynamic functions of biological organisms often rely on arrays of actively deformable microstructures undergoing a nearly unlimited repertoire of predetermined and self-regulated reconfigurations and motions, most of which are difficult or not yet possible to achieve in synthetic systems. Here, we introduce stimuli-responsive microstructures based on liquid-crystalline elastomers (LCEs) that display a broad range of hierarchical, even mechanically unfavored deformation behaviors. By polymerizing molded prepolymer in patterned magnetic fields, we encode any desired uniform mesogen orientation into the resulting LCE microstructures, which is then read out upon heating above the nematic–isotropic transition temperature (TN–I) as a specific prescribed deformation, such as twisting, in- and out-of-plane tilting, stretching, or contraction. By further introducing light-responsive moieties, we demonstrate unique multifunctionality of the LCEs capable of three actuation modes: self-regulated bending toward the light source at T < TN–I, magnetic-field–encoded predetermined deformation at T > TN–I, and direction-dependent self-regulated motion toward the light at T > TN–I. We develop approaches to create patterned arrays of microstructures with encoded multiple area-specific deformation modes and show their functions in responsive release of cargo, image concealment, and light-controlled reflectivity. We foresee that this platform can be widely applied in switchable adhesion, information encryption, autonomous antennae, energy harvesting, soft robotics, and smart buildings.

Collective fluctuation in chiral smectic phases of main‐chain liquid crystalline polymers

2007 ◽  
Vol 34 (3) ◽  
pp. 305-310 ◽  
Author(s):  
Kazuyuki Hiraoka ◽  
Takuhei Nose ◽  
Yoshiko Uematsu ◽  
Masatoshi Tokita ◽  
Junji Watanabe
Keyword(s):  
Liquid Crystalline ◽  
Main Chain ◽  
Liquid Crystalline Polymers ◽  
Crystalline Polymers ◽  
Smectic Phases

Facile Synthesis, Morphology Evolution and Tunable Luminescence of NaGdF4:Yb,Er Nanorods with Various Aspect Ratios

NANO ◽  
2018 ◽  
Vol 13 (08) ◽  
pp. 1850093 ◽  
Author(s):  
Shasha Gai ◽  
Jiqing Jiao ◽  
Wei Wei ◽  
Yao Li ◽  
Lihua Liu ◽  
...  
Keyword(s):  
Energy Level ◽  
Hydrothermal Method ◽  
Growth Mechanism ◽  
Morphology Evolution ◽  
Schematic Diagram ◽  
Facile Synthesis ◽  
Reaction Conditions ◽  
Facile Hydrothermal Method ◽  
Aspect Ratios ◽  
Lower Temperature

The well-defined NaGdF4:Yb,Er nanorods (NRs) with various aspect ratios were synthesized using a facile hydrothermal method. The morphology and crystal phase of NRs could be controlled by reaction conditions. NaGdF4:Yb,Er NRs with various aspect ratios could be synthesized and their upconversion (UC) luminescence was tuned. It is displayed that the NRs with aspect ratios about 5 exhibited the strongest UC luminescence among samples. The growth mechanism and morphology transition of NRs had been deduced by schematic diagram. And UC mechanism had been determined by energy level diagrams. Compared with previous reports, the work provided a facial method for UCNRs with various aspect ratios at lower temperature.

scholarly journals Influence of an MgTiTaON Inserted Layer on Magnetic Properties and Microstructure of FePtAgC Films

Coatings ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 238 ◽  
Author(s):  
Jai-Lin Tsai ◽  
Cheng Dai ◽  
Jyun-you Chen ◽  
Ting-Wei Hsu ◽  
Shi-Min Weng ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Cross Section ◽  
Lattice Relaxation ◽  
Fept Film ◽  
Perpendicular Magnetization ◽  
Aspect Ratios ◽  
Out Of Plane ◽  
Temperature Deposition ◽  
Critical Lattice ◽  
C 30

The FePt film above 10 nm critical lattice relaxation thickness was prepared and the ultrathin MgTiTaON layer was interleaved in between FePt film and the multilayer stack is FePt(6 nm)/[MgTiTaON(1 nm)/FePt(4 nm)]2. Next, the FePt films were co-sputtered with (Ag, C) segregants during deposition and the layer stacks is FePt(6 nm)(Ag, C)(x vol %)/[MgTiTaON (1 nm)/FePt(4 nm)(Ag, C) (x vol %)]2 (x = 0, 10, 20, 30, 40). After high temperature deposition at 470 °C, the granular FePt(Ag, C, MgTiTaON) film illustrated perpendicular magnetization and the out-of-plane coercivity (Hc) was increased with (Ag, C) segregants and the highest Hc is 18.3 kOe when x = 40. From cross-section images, the FePt layer are more continuous with 0 and 10 vol% (Ag, C) segregants and changed to an island structure when the (Ag, C) segregants increase to 20–40 vol %. The FePt grains were grown in separated islands in 20, 30 vol % (Ag, C) and changed to dense columnar-like morphology in 40 vol%. The second nucleated grains which contribute the in-plane magnetization are found in FePt (Ag, C) (40 vol %) film. The FePt islands are reached by inserting the ultrathin MgTiTaON layer and the island heights of FePt(Ag, C) (30, 40 vol %) are around 31–38 nm and the aspect ratios are 0.6–0.8.

Sign in / Sign up

Export Citation Format

Share Document