Molecular Motion Analysis of 5CB in PDLCs Using Solid-State 13C NMR Relaxation Spectroscopy

1993 ◽  
Vol 47 (7) ◽  
pp. 933-941 ◽  
Author(s):  
Karen L. Buchert ◽  
Jack L. Koenig ◽  
Shi-Qing Wang ◽  
John L. West
Keyword(s):  
Liquid Crystal ◽  
Solid State ◽  
Polymer Matrix ◽  
Nmr Relaxation ◽  
Domain Size ◽  
Chemical Structures ◽  
Similar Chemical ◽  
Polymer Dispersed ◽  
Submicron Droplets ◽  
Significant Change

In samples of polymer-dispersed liquid crystals (PDLCs), submicron droplets of liquid crystal reside within a polymer matrix. By the use of the cross polarization technique for solid-state 13C NMR spectroscopy, the NMR spectrum of the liquid crystal can be obtained without interference from the polymer spectrum, even though the two materials have some similar chemical structures. Both 13C T1 and 13C T1 ρ relaxation experiments were performed on a PDLC system of 5CB in epoxy as a function of 5CB domain size. The 13C T1 relaxation constants and the localized motions they measure showed no significant change over the liquid crystal domain size studied. However, the 13C T1 ρ relaxation constants and the segmental motions of molecules they measure revealed a significant change over the liquid crystal domain size studied. Therefore, the 13C T1 ρ values can be used to determine the change in mobility of the molecular segments of the SCB molecules resulting from increased interaction between the liquid crystal and the polymer matrix and to further understand the importance of the molecular motions of the liquid crystal in the switching phenomenon for PDLC materials.

Enhancement of Optical Transmittance of Polymer-Dispersed Liquid Crystal Cells

2015 ◽  
Vol 643 ◽  
pp. 29-32
Author(s):  
Intan Syazwani ◽  
Moriyoshi Haruyama ◽  
Hiroki Hachisuka ◽  
Gicho Sha ◽  
Wataru Kada ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Surface Treatment ◽  
Polymer Matrix ◽  
Optical Transmittance ◽  
Application Field ◽  
Polymer Dispersed Liquid Crystal ◽  
Polymer Dispersed ◽  
Crystal Cells ◽  
Network Type

Enhancement of optical transmittance of polymer-dispersed liquid crystal (PDLC) cells was investigated by introducing a modification into the substrates. Surface treatment by rubbing was performed on both network-type and droplet-type PDLCs to investigate the effect on the optical transmittance of the cells. Differences in the transmittance of the PDLC in the polymer matrix were observed by introducing rubbing effect on network-type PDLC but not on droplet-type PDLC. These phenomena might be used to distinguish the application field of both types of PDLC cells by enhancing optical transmittance and scattering properties.

Influence of the Polymer Matrix on the Bipolar and Radial Droplet Configurations within PDLC Films Examined by Infrared Spectroscopy

1993 ◽  
Vol 47 (5) ◽  
pp. 598-605 ◽  
Author(s):  
Coleen A. McFarland ◽  
Jack L. Koenig ◽  
John L. West
Keyword(s):  
Infrared Spectroscopy ◽  
Liquid Crystal ◽  
Polymer Matrix ◽  
Butyl Methacrylate ◽  
Droplet Growth ◽  
Thermally Induced ◽  
Polymer Dispersed Liquid Crystal ◽  
Polymer Dispersed ◽  
Ft Ir ◽  
Configuration Changes

The influence of the polymer matrix on the liquid crystal droplet configuration within a polymer-dispersed liquid crystal (PDLC) film is studied with the use of infrared spectroscopy. With a change of the polymer from poly( n-butyl methacrylate) to poly(isobutyl methacrylate) with the use of E7 liquid crystal, the droplet configuration changes from bipolar to radial. For both of these PDLC systems with 80:20, 70:30, and 60:40 E7/polymer compositions, the LC droplets grow in diameter with time. The spectroscopic data monitoring the droplet growth are described exponentially. A transition temperature is observed as both types of PDLCs cool, forming droplets by the thermally induced phase-separation technique. The TN-I, transition for the E7/PBMA PDLC appears at 46°C and for the E7/PIBMA PDLC appears at 51°C. Index Headings: FT-IR spectroscopy; Polymer-dispersed liquid crystals (PDLC).

Polymer Matrix on Polymer Dispersed Liquid Crystals Electro-Optical Properties

2013 ◽  
Vol 677 ◽  
pp. 183-187
Author(s):  
Huey Ling Chang ◽  
Chih Ming Chen
Keyword(s):  
Optical Properties ◽  
Liquid Crystal ◽  
Liquid Crystals ◽  
Polymer Matrix ◽  
Contrast Ratio ◽  
Butyl Methacrylate ◽  
Driving Voltage ◽  
Ethyl Methacrylate ◽  
Vis Spectroscopy ◽  
Polymer Dispersed

Polymer dispersed liquid crystal (PDLC) films are fabricated with various compositions of E7 liquid crystal (LC), 2-Hydroxy ethyl methacrylate (HEMA), Methyl methacrylate (MMA), n-butyl methacrylate (nBMA), Ethyl methacrylate (EMA), Tetraethylene glycol diacrylate (TEGDA), and Benzoin. The results show that the refractive index of the PDLC films is insensitive to the monomer side groups. The effects of different monomers addition on the microstructure, the corresponding polymer matrix motion and electro-optical properties of the PDLC samples are examined using Dynamic Mechanical Analyzers (DMA) and UV-Vis spectroscopy, respectively. The experimental results reveal that the addition of HEMA and TEGDA yields a considerable improvement in the electro-optical properties and the contrast ratio. Overall, the results show that a PDLC comprising 40wt% E7 liquid crystals, 50mol% TeGDA and 50mol% HEMA has both a high contrast ratio (12.75:1) and a low driving voltage (16 V), and is therefore a suitable candidate for smart window and a wide variety of intelligent photoelectric applications.

Molecular Motion Analysis of E7 in PDLCs as a Function of Droplet Size Using Solid-State 13C NMR Relaxation Spectroscopy

1993 ◽  
Vol 47 (7) ◽  
pp. 942-951 ◽  
Author(s):  
Karen L. Buchert ◽  
Jack L. Koenig ◽  
Shi-Qing Wang ◽  
John L. West
Keyword(s):  
Liquid Crystal ◽  
Droplet Size ◽  
Molecular Motion ◽  
Nmr Relaxation ◽  
Molecular Motions ◽  
Segmental Mobility ◽  
Switching Phenomenon ◽  
Polymer Dispersed Liquid Crystals ◽  
Polymer Dispersed ◽  
Relaxation Experiments

13C NMR relaxation spectroscopy as applied to polymer-dispersed liquid crystals (PDLCs) provides a method for measuring the molecular motions of the liquid crystal molecules within droplets dispersed throughout the material's polymer matrix. Because liquid crystal molecular motion may play a major role in the switching phenomenon of PDLC materials from an opaque film to a clear film, both T1 and T1ρ relaxation experiments are used to measure molecular mobility of the liquid crystal as a function of droplet size for PDLC materials made of E7 and epoxy. The segmental molecular motions measured by T1ρ relaxation show a significant dependence on liquid crystal droplet size. Three models are provided which explain the observed restriction in segmental mobility of the liquid crystal molecules as the droplet size decreases and the polymer/liquid crystal interaction increases.

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