scholarly journals Ultrafast isomerization-induced cooperative motions to higher molecular orientation in smectic liquid-crystalline azobenzene molecules

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Masaki Hada ◽  
Daisuke Yamaguchi ◽  
Tadahiko Ishikawa ◽  
Takayoshi Sawa ◽  
Kenji Tsuruta ◽  
...  
Keyword(s):  
Molecular Orientation ◽  
Soft Matter ◽  
Liquid Crystalline ◽  
Laser Polarization ◽  
Time Resolved ◽  
Cooperative Motion ◽  
Subsequent Response ◽  
Molecular Dynamics Calculations ◽  
Polarization Axis ◽  
Linearly Polarized

Abstract The photoisomerization of molecules is widely used to control the structure of soft matter in both natural and synthetic systems. However, the structural dynamics of the molecules during isomerization and their subsequent response are difficult to elucidate due to their complex and ultrafast nature. Herein, we describe the ultrafast formation of higher-orientation of liquid-crystalline (LC) azobenzene molecules via linearly polarized ultraviolet light (UV) using ultrafast time-resolved electron diffraction. The ultrafast orientation is caused by the trans-to-cis isomerization of the azobenzene molecules. Our observations are consistent with simplified molecular dynamics calculations that revealed that the molecules are aligned with the laser polarization axis by their cooperative motion after photoisomerization. This insight advances the fundamental chemistry of photoresponsive molecules in soft matter as well as their ultrafast photomechanical applications.

scholarly journals Linearly Polarized UV Light-Induced Optical Anisotropy of PVA Films and Flexible Macrocycle Schiff Base Ni(II), Cu(II), Zn(II) Dinuclear Complexes

Symmetry ◽  
2018 ◽  
Vol 10 (12) ◽  
pp. 760
Author(s):  
Masahiro Takase ◽  
Shiomi Yagi ◽  
Tomoyuki Haraguchi ◽  
Shabana Noor ◽  
Takashiro Akitsu
Keyword(s):  
Optical Anisotropy ◽  
Molecular Orientation ◽  
Soft Matter ◽  
Uv Light ◽  
Polarized Light ◽  
X Ray ◽  
Crystallographic Symmetry ◽  
Linearly Polarized ◽  
Dinuclear Metal Complexes ◽  
Crystal Structural

Three dinuclear metal complexes (comprised of six-coordinated nNi2L and five-coordinated nCu2L and nZn2L) were confirmed by means of elemental analysis, UV-vis and IR spectra, and single X-ray crystal structural analysis in a spectroscopic study. The stable structures of these nNi2L, nCu2L, and nZn2L complexes in poly(vinylalcohol) (PVA) films were analyzed using UV-vis spectra. The molecular orientation of hybrid PVA film materials after linearly polarized light irradiation was analyzed to obtain the polarized spectra and dichroic ratio. Among the three materials, nNi2L and nZn2L complexes indicated an increasing optical anisotropy that depended on the flexibility of the complexes. We have included a discussion on the formation of the pseudo-crystallographic symmetry of the components in a soft matter (PVA films).

Observing the relaxation of molecular orientation in sheared liquid crystalline polymer solutions

1990 ◽  
Vol 48 (4) ◽  
pp. 1092-1093
Author(s):  
Wendy Putnam ◽  
Christopher Viney
Keyword(s):  
Molecular Orientation ◽  
Liquid Crystalline Polymer ◽  
Liquid Crystalline ◽  
Crystalline Polymer ◽  
Polymer Processing ◽  
Molecular Alignment ◽  
Global Alignment ◽  
Shear Direction ◽  
Axial Strength ◽  
Strength And Stiffness

Liquid crystalline polymers (solutions or melts) can be spun into fibers and films that have a higher axial strength and stiffness than conventionally processed polymers. These superior properties are due to the spontaneous molecular extension and alignment that is characteristic of liquid crystalline phases. Much of the effort in processing conventional polymers goes into extending and aligning the chains, while, in liquid crystalline polymer processing, the primary microstructural rearrangement involves converting local molecular alignment into global molecular alignment. Unfortunately, the global alignment introduced by processing relaxes quickly upon cessation of shear, and the molecular orientation develops a periodic misalignment relative to the shear direction. The axial strength and stiffness are reduced by this relaxation.Clearly there is a need to solidify the liquid crystalline state (i.e. remove heat or solvent) before significant relaxation occurs. Several researchers have observed this relaxation, mainly in solutions of hydroxypropyl cellulose (HPC) because they are lyotropic under ambient conditions.

Charge mobility in discotic liquid crystalline porphyrins and phthalocyanines measured by PR-TRMC

2003 ◽  
Vol 07 (05) ◽  
pp. 342-350 ◽  
Author(s):  
John M. Warman ◽  
Jessica E. Kroeze ◽  
Pieter G. Schouten ◽  
Anick M. van de Craats
Keyword(s):  
Conjugated Polymers ◽  
Carrier Mobility ◽  
Liquid Crystalline ◽  
Alkyl Chain ◽  
Charge Carrier Mobility ◽  
Chain Structure ◽  
Coupling Element ◽  
Time Resolved ◽  
Liquid Crystalline Phases ◽  
Conductive Properties

The pulse-radiolysis time-resolved microwave conductivity technique, “PR-TRMC”, has been used to determine the charge carrier mobility within columnar stacks of mesomorphic discotic porphyrins and phthalocyanines. The influences of temperature, morphology and variations in the primary molecular structure are demonstrated and discussed. Both the mesomorphic and conductive properties are shown to be dramatically influenced by subtle changes in the peripheral alkyl chain structure or the core-to-chain coupling element. Mobilities close to 1 cm2.V−1.s−1 are found in crystalline solids, and well in excess of 0.1 cm2.V−1.s−1 in columnar, liquid crystalline phases. These values which are even larger than those determined by PR-TRMC for conjugated polymers and similar to values found for electrons and holes in organic single crystals.

MOLECULAR ORIENTATION AND ELECTROHYDRODYNAMIC FLOW IN HOMOGENEOUS ER FLUIDS

2001 ◽  
Vol 15 (06n07) ◽  
pp. 973-979 ◽  
Author(s):  
HIROKI IWATSUKI ◽  
NAOTO GOHKO ◽  
HIROSHI KIMURA ◽  
YUICHI MASUBUCHI ◽  
JUN-ICHI TAKIMOTO ◽  
...  
Keyword(s):  
Liquid Crystals ◽  
Electric Field ◽  
Molecular Orientation ◽  
Liquid Crystalline ◽  
Polypropylene Glycol ◽  
Homogeneous Fluid ◽  
Immiscible Liquids ◽  
Electrohydrodynamic Flow ◽  
Er Fluids ◽  
Er Fluid

Homogeneous ER fluid is an ER fluid which consists of a homogeneous fluid only; it is neither a suspension nor a blend of immiscible liquids. Various liquid crystals are typical examples of homogeneous ER fluids. Recently, we have found that urethane-modified polypropylene glycol (UPPG) is one of the very few examples of homogeneous ER fluids which show no liquid crystalline order. In order to clarify the mechanism of the ER effect in this fluid, we have studied, in this paper, electrohydrodynamic flow under shear and electric field.

Real-Time Pursuit of Crystal Growth by Millisecond Time-Resolved Multichannel Fourier Transform Infrared Spectroscopy

1998 ◽  
Vol 52 (2) ◽  
pp. 222-225
Author(s):  
Mamoru Hashimoto ◽  
Hiro-O Hamaguchi
Keyword(s):  
Fourier Transform ◽  
Infrared Spectroscopy ◽  
Structural Change ◽  
Liquid Phase ◽  
Fourier Transform Infrared Spectroscopy ◽  
Molecular Orientation ◽  
Structural Changes ◽  
Fourier Transform Infrared ◽  
Time Resolved ◽  
Recovery Curves

The surface (about 130 molecular layers) of an oriented thin crystal of decanoic acid was subjected to sudden melting by a laser-induced temperature jump (T-jump), and the process of subsequent crystal re-growth was monitored by millisecond time-resolved multichannel Fourier transform infrared spectroscopy. The gauche–trans structural change of the alkane part of the molecule has been probed by the CH stretch bands in the 2800–3000 cm−1 region. The change in the molecular orientation has been detected by the OH stretch band around 3065 cm−1. The recovery curves for the CH2 antisymmetric stretch and the OH stretch bands are markedly different from each other in the first 200 ms, suggesting that the gauche–trans structural changes precedes the crystal re-growth. After 500 ms, the recovery curves become identical. This result means that the rate of the gauche to the trans structural change is equal to the rate of the recovery of the molecular orientation. It is highly likely that a fast equilibrium is attained between the gauche and the trans conformations in the liquid phase after 500 ms from the sudden melting and that the crystal re-growth takes place solely via the all-trans structure in the liquid phase.

correlations of mechanical properties and microstructural parameters in annealed drawn film of liquid crystalline polymer in situ reinforced PP

e-Polymers ◽  
2011 ◽  
Vol 11 (1) ◽  
Author(s):  
Sayant Saengsuwan
Keyword(s):  
Mechanical Properties ◽  
Annealing Time ◽  
Crystalline Phase ◽  
Molecular Orientation ◽  
Liquid Crystalline Polymer ◽  
Liquid Crystalline ◽  
Crystalline Polymer ◽  
Relative Level ◽  
Microstructural Parameters

AbstractDrawn composite thin film based on thermotropic liquid crystalline polymer (TLCP) and polypropylene (PP) was annealed at 130 °C at different times. The influence of annealing time on microstructural and mechanical properties of the composite film has been studied. The correlation in mechanical properties and their microstructural parameters has also been investigated. X-Ray diffraction results reveal that the smectic mesophase transforms progressively into the monoclinic phase as annealing time is increased. Consequently, the true crystallinity (Xc), crystal thickness (L) as well as relative level of molecular orientation of PP crystalline phase in the annealed TLCP/PP films are increased significantly. Also, the TLCP fibrils have no influence on the microstructure of PP crystalline phase. The apparent crystallinity (Xc,a) of PP phase evaluated by DSC also increase significantly with annealing time. As a result, the increases of these microstructural parameters coupled with the reinforcement of TLCP fibrils could be contributed directly to the remarkable enhancement of mechanical properties of the annealed TLCP/PP film in both machine (MD) and transverse (TD) directions. The correlation of moduli with microstructural parameters (Xc, Xc,a and L) exhibits nonlinear relations. However, the relative level of molecular orientation is a more suitable parameter to correlate with the improvement of mechanical properties of the annealed TLCP/PP film. Finally, this work presents that the mechanical properties of the TLCP in situ reinforced thermoplastics can be significantly enhanced via a simple thermal treatment.

Electric-Field-Induced Reorientation of Liquid Crystalline p-Cyanophenyl-p-n-Alkylbenzoates: A Time-Resolved Study by Fourier Transform Infrared Transmission and Attenuated Total Reflection Spectroscopy

2003 ◽  
Vol 57 (5) ◽  
pp. 499-505 ◽  
Author(s):  
E. Klimov ◽  
M. Fuelleborn ◽  
H. W. Siesler
Keyword(s):  
Fourier Transform ◽  
Electric Field ◽  
Liquid Crystalline ◽  
External Perturbation ◽  
Fourier Transform Infrared ◽  
Surface Region ◽  
Total Reflection ◽  
Attenuated Total Reflection ◽  
Infrared Transmission ◽  
Time Resolved

Time-resolved polarization Fourier transform infrared (FT-IR) transmission and attenuated total reflection (ATR) spectroscopy were applied to investigate the reorientation phenomena of the three members of the homologous series of nematic liquid crystalline p-cyanophenyl-p-n-alkylbenzoates 6CPB, 7CPB, and 10CPB under the external perturbation of an electric field. In conjunction with a newly constructed measurement cell, this method allowed us to differentiate the response of the LC system in the surface layer and in the bulk of the cell at different temperatures and voltages. The relaxation time of the LC molecules close to the wall of the cell was found to be shorter than in the bulk. However, at a field strength of 7 V, the initial orientation in the bulk preceeds the analogous process in the surface region.

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