Effect of residual linear orientation on the optical properties of cholesteric films

1988 ◽  
Vol 66 (9) ◽  
pp. 2229-2233 ◽  
Author(s):  
Anna M. Ritcey ◽  
Gérard Charlet ◽  
Derek G. Gray
Keyword(s):  
Liquid Crystalline ◽  
Potential Problem ◽  
Polarization State ◽  
Polarized Light ◽  
Hydroxypropyl Cellulose ◽  
Reflection Band ◽  
Selective Reflection ◽  
Circularly Polarized Light ◽  
Oriented Film ◽  
Simple Consideration

The apparent circular dichroism arising from the selective reflection of circularly polarized light by cholesteric films of (hydroxypropyl)cellulose is extremely sensitive to residual linear orientation. The introduction of a uniaxially oriented film in the spectropolarimeter beam in front of a liquid crystalline sample may change both the intensity and the sign of the observed mesophase reflection band. The results can be understood by a simple consideration of the way in which the polarization state of light is altered as it traverses the birefringent film. These observations emphasize a potential problem in the use of circular reflectivity as a method to characterize the reflection properties of polymeric cholesteric liquid crystals. The presence of linear orientation in such samples can give rise to artifacts.

Study of Casting Self-Colored Liquid Crystalline Solid Films of Hydroxypropyl Cellulose

2013 ◽  
Vol 341-342 ◽  
pp. 217-220
Author(s):  
Qin Xing Zhang ◽  
Li Qian ◽  
Li Xia Wang ◽  
S. Stuto ◽  
Chang Yu Shen
Keyword(s):  
Visible Light ◽  
Liquid Crystalline ◽  
Solution Concentration ◽  
Hydroxypropyl Cellulose ◽  
Crystalline Solid ◽  
Selective Reflection ◽  
Solid Films ◽  
Colored Coating ◽  
Cooling Velocity ◽  
Cholesteric Liquid Crystalline

Solutions of lyotropic cholesteric liquid crystalline hydroxypropyl cellulose (HPC) in water would be self-colored due to the selective reflection of visible light, depending on the solution concentration. Colored coating of the liquid crystalline aqueous HPC solutions was attempted to apply. HPC solid films were found which could cast from the liquid crystalline solutions at different conditions such as solution concentration and different drying temperature. Experiments show that both solution concentration and cooling velocity play an important effect in controlling the color of HPC films.

scholarly journals LIQUID CRYSTALLINE PROPERTIES OF HYDROXYPROPYL CELLULOSE PREPARED FROM DISSOLVED EGYPTIAN BAGASSE PULP

2021 ◽  
Vol 55 (1-2) ◽  
pp. 13-22
Author(s):  
ABOU-ZEID RAGAB E. ◽  
NAHLA A. EL-WAKIL ◽  
AHMED ELGENDY ◽  
YEHIA FAHMY ◽  
ALAIN DUFRESNE
Keyword(s):  
Molecular Structure ◽  
1H Nmr Spectroscopy ◽  
Liquid Crystalline ◽  
Critical Concentration ◽  
Polarized Light ◽  
Hydroxypropyl Cellulose ◽  
Scanning Calorimetry ◽  
Dimethyl Acetamide ◽  
Ft Ir ◽  
Bagasse Pulp

"Egyptian agricultural wastes were used for preparing advanced cellulosic derivatives possessing liquid crystalline properties. Cellulose was successfully isolated in pure form from Egyptian bagasse pulp. Hydroxypropylation was carried out on the obtained cellulose and the liquid crystalline properties were investigated. The prepared hydroxypropyl cellulose (HPC) was esterified with 4-alkyloxybenzoic acids, giving products with liquid crystalline properties. The molecular structure of HPC and a series of its esters – 4-alkoxybenzoloxypropyl cellulose (ABPC-m) – was confirmed by Fourier transform infrared (FT-IR) and 1H NMR spectroscopy. The liquid crystalline (LC) phases and transition behaviors were investigated using differential scanning calorimetry (DSC) and polarized light microscopy (PLM). The lyotropic behavior in dimethyl acetamide (DMA) was investigated using an Abee refractometer, and the critical concentration was determined by measuring the refractive index of the solutions in DMA."

scholarly journals Circularly Polarized Light Detection by Chiral Photonic Cellulose Nanocrystal with ZnO Photoconductive Layer in Ultraviolet Region

Nanomaterials ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 3098
Author(s):  
Boyu Zhang ◽  
Sixiang Zhao ◽  
Yingying Yu ◽  
Ming Li ◽  
Liancheng Zhao ◽  
...  
Keyword(s):  
Self Assembly ◽  
Polarization State ◽  
Polarized Light ◽  
Cellulose Nanocrystal ◽  
Ultraviolet Region ◽  
Circularly Polarized Light ◽  
Circularly Polarized ◽  
Left Handed ◽  
Chiral Nematic ◽  
Wide Range

Circularly polarized light (CPL) detection and polarization state recognition are required for a wide range of applications. Conventional polarization detection with optical components causes difficulties for miniaturization and integration. An effective design strategy is proposed for direct CPL detection with chiral material. Here, we realized direct CPL detection based on the combination of chiral photonic cellulose nanocrystal (CNC) and ultraviolet-sensitive ZnO photoconductive material. The CNC layer deposited by evaporation-induced self-assembly established the left-handed chiral nematic structure with a photonic bandgap (PBG) to recognize left-handed CPL (LCPL) and right-handed CPL (RCPL) at specific wavelengths. The PBG of CNC layer has been modulated by the adjustment of chiral nematic pitch to match the semiconductor bandgap of ZnO film in ultraviolet region. The photocurrents under RCPL and LCPL are 2.23 × 10−6 A and 1.77 × 10−6 A respectively and the anisotropy factor Δgpc of 0.23 is acquired for the CPL detection based on the chiral photonic CNC. This design provides a new approach to the detection of CPL polarization state with competitive performance.

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.

Sign in / Sign up

Export Citation Format

Share Document