Tunable liquid crystal waveguide devices for filter and sensor applications

2005 ◽  
Author(s):  
I. J. G. Sparrow ◽  
A. Dyadyusha ◽  
M. Kaczmarek ◽  
G. D. Emmerson ◽  
P. G. R. Smith
Keyword(s):  
Liquid Crystal ◽  
Sensor Applications ◽  
Waveguide Devices

scholarly journals Effect of Crosslinkers on Optical and Mechanical Behavior of Chiral Nematic Liquid Crystal Elastomers

Molecules ◽  
2021 ◽  
Vol 26 (20) ◽  
pp. 6193
Author(s):  
Kyosun Ku ◽  
Kyohei Hisano ◽  
Kyoko Yuasa ◽  
Tomoki Shigeyama ◽  
Norihisa Akamatsu ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Polymer Network ◽  
Molar Ratio ◽  
Stimuli Responsive ◽  
Breaking Strain ◽  
Responsive Materials ◽  
Sensor Applications ◽  
Color Changes ◽  
Chiral Nematic ◽  
Liquid Crystal Elastomers

Chiral nematic (N*) liquid crystal elastomers (LCEs) are suitable for fabricating stimuli-responsive materials. As crosslinkers considerably affect the N*LCE network, we investigated the effects of crosslinking units on the physical properties of N*LCEs. The N*LCEs were synthesized with different types of crosslinkers, and the relationship between the N*LC polymeric system and the crosslinking unit was investigated. The N*LCEs emit color by selective reflection, in which the color changes in response to mechanical deformation. The LC-type crosslinker decreases the helical twisting power of the N*LCE by increasing the total molar ratio of the mesogenic compound. The N*LCE exhibits mechano-responsive color changes by coupling the N*LC orientation and the polymer network, where the N*LCEs exhibit different degrees of pitch variation depending on the crosslinker. Moreover, the LC-type crosslinker increases the Young’s modulus of N*LCEs, and the long methylene chains increase the breaking strain. An analysis of experimental results verified the effect of the crosslinkers, providing a design rationale for N*LCE materials in mechano-optical sensor applications.

Fabrication of polymer waveguide devices for sensor applications

2010 ◽  
Author(s):  
Mu Cheng ◽  
Jussi Hiltunen ◽  
Meng Wang ◽  
Antti Suutala ◽  
Pentti Karioja ◽  
...  
Keyword(s):  
Polymer Waveguide ◽  
Sensor Applications ◽  
Waveguide Devices

Liquid crystal waveguide devices

2011 ◽  
Author(s):  
A. d'Alessandro ◽  
R. Asquini ◽  
M. Trotta ◽  
R. Beccherelli
Keyword(s):  
Liquid Crystal ◽  
Waveguide Devices

scholarly journals Environmentally Stable Chiral-Nematic Liquid-Crystal Elastomers with Mechano-Optical Properties

2021 ◽  
Vol 11 (11) ◽  
pp. 5037
Author(s):  
Kyosun Ku ◽  
Kyohei Hisano ◽  
Seiya Kimura ◽  
Tomoki Shigeyama ◽  
Norihisa Akamatsu ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Liquid Crystal ◽  
Nematic Liquid Crystal ◽  
Optical Sensors ◽  
Polymer Network ◽  
Sensor Applications ◽  
Chiral Nematic ◽  
Cross Links ◽  
Responsive Behavior ◽  
Liquid Crystal Elastomers

Chiral-nematic liquid crystal (N* LC) elastomers exhibit mechano-optical responsive behavior. However, practical sensor applications have been limited by the intrinsic sensitivity of N* LC elastomers to environmental conditions, such as temperature. Although densely cross-linked LC network polymers exhibit high thermal stability, they are not proper for the mechanical sensor due to high glass transition temperatures and low flexibility. To overcome these issues, we focused on enhancing thermal stability by introducing noncovalent cross-linking sites via intermolecular interactions between LC molecules bonded to the polymer network. N* LC elastomers with a cyanobiphenyl derivative as a side-chain mesogen exhibited mechano-optical responsive behavior, with a hypsochromic shift of the reflection peak wavelength under an applied tensile strain and quick shape and color recovery owing to high elasticity. Notably, the N* LC elastomers showed high resistance to harsh environments, including high temperatures and various solvents. Interactions, such as π–π stacking and dipole–dipole interactions, between the cyanobiphenyl units can act as weak cross-links, thus improving the thermal stability of the LC phase without affecting the mechano-optical response. Thus, these N* LC elastomers have great potential for the realization of practical mechano-optical sensors.

Freeze-fracture TEM of the helical smectic A* phase

1992 ◽  
Vol 50 (1) ◽  
pp. 278-279
Author(s):  
K.J. Ihn ◽  
R. Pindak ◽  
J. A. N. Zasadzinski
Keyword(s):  
Liquid Crystal ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Freeze Fracture ◽  
Smectic Phase ◽  
Layer Spacing ◽  
Screw Dislocations ◽  
Smectic A ◽  
Smectic Phases ◽  
Discrete Amount

A new liquid crystal (called the smectic-A* phase) that combines cholesteric twist and smectic layering was a surprise as smectic phases preclude twist distortions. However, the twist grain boundary (TGB) model of Renn and Lubensky predicted a defect-mediated smectic phase that incorporates cholesteric twist by a lattice of screw dislocations. The TGB model for the liquid crystal analog of the Abrikosov phase of superconductors consists of regularly spaced grain boundaries of screw dislocations, parallel to each other within the grain boundary, but rotated by a fixed angle with respect to adjacent grain boundaries. The dislocations divide the layers into blocks which rotate by a discrete amount, Δθ, given by the ratio of the layer spacing, d, to the distance between grain boundaries, lb; Δθ ≈ d/lb (Fig. 1).

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