Anomalous Cis Isomer Orientation in a Liquid Crystalline Azo Polymer on Irradiation with Linearly-Polarized Light

2003 ◽  
Vol 107 (10) ◽  
pp. 2197-2204 ◽  
Author(s):  
Dennis K. Hore ◽  
Almeria L. Natansohn ◽  
Paul L. Rochon
Keyword(s):  
Liquid Crystalline ◽  
Polarized Light ◽  
Azo Polymer ◽  
Linearly Polarized ◽  
Cis Isomer

scholarly journals Thermocapillary Marangoni Flows in Azopolymers

Materials ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2464
Author(s):  
Andrzej Miniewicz ◽  
Anna Sobolewska ◽  
Wojciech Piotrowski ◽  
Pawel Karpinski ◽  
Stanislaw Bartkiewicz ◽  
...  
Keyword(s):  
Liquid Crystalline ◽  
Mass Movement ◽  
Polymer Surface ◽  
Polarized Light ◽  
Marangoni Effect ◽  
Mass Motion ◽  
Polymeric Liquid ◽  
Force Microscopy ◽  
Atomic Force ◽  
Linearly Polarized

It is well known that light-induced multiple trans-cis-trans photoisomerizations of azobenzene derivatives attached to various matrices (polymeric, liquid crystalline polymers) result in polymer mass movement leading to generation of surface reliefs. The reliefs can be produced at small as well as at large light intensities. When linearly polarized light is used in the process, directional photo-induced molecular orientation of the azo molecules occurs, which leads to the generation of optical anisotropy in the system, providing that thermal effects are negligible. On the other hand, large reliefs are observed at relatively strong laser intensities when the optofluidization process is particularly effective. In this article, we describe the competitive thermocapillary Marangoni effect of polymer mass motion. We experimentally prove that the Marangoni effect occurs simultaneously with the optofluidization process. It destroys the orientation of the azopolymer molecules and results in cancelation of the photo-induced birefringence. Our experimental observations of polymer surface topography with atomic force microscopy are supported by suitable modelings.

Laser manipulation in liquid crystals: an approach to microfluidics and micromachines

2006 ◽  
Vol 364 (1847) ◽  
pp. 2789-2805 ◽  
Author(s):  
Helen F Gleeson ◽  
Tiffany A Wood ◽  
Mark Dickinson
Keyword(s):  
Liquid Crystals ◽  
Liquid Crystalline ◽  
Polarized Light ◽  
Three Dimensions ◽  
Laser Tweezers ◽  
Fluid Medium ◽  
Circularly Polarized Light ◽  
Viscosity Coefficients ◽  
Linearly Polarized ◽  
Local Shear

Laser trapping of particles in three dimensions can occur as a result of the refraction of strongly focused light through micrometre-sized particles. The use of this effect to produce laser tweezers is extremely common in fields such as biology, but it is only relatively recently that the technique has been applied to liquid crystals (LCs). The possibilities are exciting: droplets of LCs can be trapped, moved and rotated in an isotropic fluid medium, or both particles and defects can be trapped and manipulated within a liquid crystalline medium. This paper considers both the possibilities. The mechanism of transfer of optical angular momentum from circularly polarized light to small droplets of nematic LCs is described. Further, it is shown that droplets of chiral LCs can be made to rotate when illuminated with linearly polarized light and possible mechanisms are discussed. The trapping and manipulation of micrometre-sized particles in an aligned LC medium is used to provide a measure of local shear viscosity coefficients and a unique test of theory at low Ericksen number in LCs.

Azobenzene-containing liquid crystalline block copolymer supramolecular complexes as a platform for photopatternable colorless materials

2020 ◽  
Vol 8 (4) ◽  
pp. 1225-1230
Author(s):  
Miron Bugakov ◽  
Natalia Boiko ◽  
Sergey Abramchuk ◽  
Xiaomin Zhu ◽  
Valery Shibaev
Keyword(s):  
Block Copolymer ◽  
Triblock Copolymer ◽  
Liquid Crystalline ◽  
Polarized Light ◽  
Supramolecular Complexes ◽  
Linearly Polarized ◽  
Hydrogen Bonded

Using liquid crystalline triblock copolymer complexes with hydrogen-bonded azobenzene moieties, photopatterned colorless birefringent films were prepared by irradiation with linearly polarized light and subsequent extracting azobenzene moieties.

Oriental behaviour of some homologues of 4-n-pentyl-phenylthio-4′-n-alkoxybenzoate doped with dichroic dye

2008 ◽  
Vol 16 (3) ◽  
Author(s):  
D. Bauman ◽  
A. Zięba ◽  
E. Mykowska
Keyword(s):  
Liquid Crystal ◽  
Order Parameter ◽  
Liquid Crystalline ◽  
Orientational Order ◽  
Polarized Light ◽  
Emission Spectra ◽  
Smectic C ◽  
Fluorescence Measurements ◽  
Dichroic Dye ◽  
Linearly Polarized

AbstractThe long-range orientational order of three members of 4-n-pentylphenylthio-4′-n-alkoxybenzoate $$ (\bar nS5) $$ series doped with a dichroic dye was studied by means of electronic absorption and fluorescence measurements. The order parameters <P2> and <P4> as well as the orientational distribution function were determined on the basis of absorption and emission spectra of linearly polarized light recorded as a function of temperature in the nematic, smectic A, and smectic C phases. An influence of the dye molecular structure on the orientational order of the dye/liquid crystal mixture was observed. Moreover, the dependence of the order parameter values on the length of the alkoxy chain in liquid crystal molecules was found. It was shown that the order parameter <P4>, obtained from fluorescence measurements, can be helpful in recognizing the second-order or weakly first-order transitions between various liquid crystalline phases.

Cholesteric liquid crystalline siloxanes with azo dye. Generation of additional reflection bands with linearly polarized light

1993 ◽  
Vol 15 (1) ◽  
pp. 113-121 ◽  
Author(s):  
A. Petri ◽  
Ch. Bräuchle ◽  
H. Leigeber ◽  
A. Miller ◽  
H.-P. Weitzel ◽  
...  
Keyword(s):  
Azo Dye ◽  
Liquid Crystalline ◽  
Polarized Light ◽  
Linearly Polarized ◽  
Cholesteric Liquid Crystalline

Photoinduced bending and unbending behavior of liquid-crystalline gels and elastomers

2004 ◽  
Vol 76 (7-8) ◽  
pp. 1467-1477 ◽  
Author(s):  
Yanlei Yu ◽  
M. Nakano ◽  
T. Ikeda
Keyword(s):  
Visible Light ◽  
Liquid Crystalline ◽  
Polarized Light ◽  
Polarization Direction ◽  
Linearly Polarized

Liquid-crystalline gels and elastomers were prepared by polymerization of mixtures containing azobenzene monomers and cross linkers with azobenzene moieties. Oriented liquid-crystalline gels and elastomer films were found to undergo anisotropic bending and unbending behavior only along the rubbing direction, when exposed to alternate irradiation of unpolarized UV and visible light. In the case of polydomain liquid-crystalline elastomer films, the bending and unbending were induced exactly along the polarization direction of incident linearly polarized light. By altering the polarization direction of light, a single film could be bent repeatedly and precisely along any chosen direction.

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