Fluctuations in Confined Liquid Crystals above Nematic-Isotropic Phase Transition Temperature

1997 ◽  
Vol 78 (4) ◽  
pp. 682-685 ◽  
Author(s):  
P. Ziherl ◽  
S. Z̆umer
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Liquid Crystals ◽  
Phase Transition Temperature ◽  
Isotropic Phase ◽  
Confined Liquid Crystals

scholarly journals Confinement Effect in a Thick Layer of LC Lanthanide Complex

Proceedings ◽  
2018 ◽  
Vol 2 (14) ◽  
pp. 1118
Author(s):  
Irina Lezova ◽  
Galina Polushina ◽  
Sergey Polushin
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Liquid Crystals ◽  
Phase Transition Temperature ◽  
Lanthanide Complex ◽  
Thick Layer ◽  
Molecular Complexes ◽  
Confinement Effect ◽  
Isotropic Phase ◽  
Crystal Complex

The structure of metallomesogen complexes differs essentially from that of calamitic liquid crystals, which emerges in their physical properties. We studied anomalous features of the transition from the nematic to isotropic phase in the ytterbium-based liquid crystal complex. For this, two approaches were used. In the first approach, we showed that the experimental values of the dielectric and optical anisotropies measured near the phase transition turned out to be substantially smaller than their calculated values. This evidently occurs because the phase transition temperature in the deep region of the experimental cell differs from that near the surface of the cell. Secondly, the temperature of N–I transitions in metallomesogenic layers within glass sandwich cells is obtained directly by means of the polarization microscope method. It was found that the phase transition temperature drops in more than ten degrees when reducing the metallomesogenic layer thickness from 200 to 5 microns. The calamite liquid crystals show the confinement effect only within the interstice of the specific size smaller than one micron. An anomalous confinement effect can be caused by a strong interaction of the molecular complexes with each other.

Shift of the nematic–isotropic phase transition temperature in a thin layer of a metallomesogenic complex

2016 ◽  
Vol 471 (2) ◽  
pp. 199-202 ◽  
Author(s):  
S. G. Polushin ◽  
V. B. Rogozhin ◽  
G. E. Polushina ◽  
I. E. Lezova ◽  
E. I. Rjumtsev ◽  
...  
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Thin Layer ◽  
Phase Transition Temperature ◽  
Isotropic Phase

A Hexagonal Pillar Array of Thermo-responsive Soft Actuators Prepared by Nanoimprinting

2011 ◽  
Vol 1312 ◽  
Author(s):  
Ching-Mao Wu ◽  
Szu-Yin Lin ◽  
Kuo-Tung Huang
Keyword(s):  
Phase Transition ◽  
Liquid Crystal ◽  
Transition Temperature ◽  
Phase Transition Temperature ◽  
Polymer Network ◽  
Isotropic Phase ◽  
Hexagonal Array ◽  
Soft Actuators ◽  
Response To Temperature ◽  
Thermomechanical Effects

ABSTRACTThermo-responsive actuation (thermomechanical effects) based on nematic liquid crystal elastomers (LCEs) have become a research priority in the preparation of soft actuators. Nematic LCEs combine the anisotropic features of liquid crystal phases with the rubber elasticity of polymer network. When heated at nematic to isotropic phase transition temperature (N-to-I temp.), a uniaxial thermomechanical deformation of LCEs will undergo at nearly constant volume due to a change of LC director order. Recently, an array of the micro-sized LCE pillars related to such thermomechanical effects have been successfully constructed through a soft lithography technology (i.e., replica molding). The prepared LCE pillars are mono-dispersive and micro-sized. They also possess N-to-I temp. higher than 100°C, largely limiting the available application. By contrast, the present study will report a hexagonal array of nano-sized thermo-responsive pillar actuators that are able to contract and expand in response to temperature changes around a lower N-to-I temp. is manufactured via using reactive rod-like liquid crystal and ultraviolet nanoimprinting technology. According to atomic force microscope (AFM) observation, a hexagonal array of pillars can be easily constructed by nanoimprinting and a responsive surface with a thermo-stimuli-driven roughness change is achieved. The room-temperature AFM scans quantitatively represent the single pillar shows a diameter of ca. 270 nm and 140 nm in depth, and the pitch meaning the averaged inter-pillar distance is measured as ca. 425 nm, thus lying in a nano-sized range. Furthermore, temperature-variable AFM is also utilized to demonstrate the pillar behaves as a thermally-stimulated nano-sized actuator. In our case, when heated above N-to-I phase transition temperature (ca. 65°C), it is clearly observed that the pillar diameter is expanded in the order of over 12-15 % and then reversibly contracted in response to temperature drop.

Photoresponsive iodine-bonded liquid crystals based on azopyridine derivatives with a low phase-transition temperature

2018 ◽  
Vol 46 (1) ◽  
pp. 37-44 ◽  
Author(s):  
Meiling Du ◽  
Luhai Li ◽  
Jingting Zhang ◽  
Kexuan Li ◽  
Meijuan Cao ◽  
...  
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Liquid Crystals ◽  
Phase Transition Temperature
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