Polymerization Effects on the Electro-Optic Properties of a Polymer Stabilized Ferroelectric Liquid Crystal

1996 ◽  
Vol 425 ◽  
Author(s):  
C. Allan Guymon ◽  
Lisa A. Dougan ◽  
Erik N. Hoggan ◽  
Christopher N. Bowman
Keyword(s):  
Liquid Crystal ◽  
Polymer Network ◽  
Polymeric Materials ◽  
Ferroelectric Polarization ◽  
Mechanical Shock ◽  
Switching Speed ◽  
Ferroelectric Liquid Crystals ◽  
Electro Optic ◽  
Polymerization Behavior ◽  
Display Technology

AbstractThe introduction of polymeric materials into liquid crystal (LC) matrices has been the focus of much interest in recent years. When a small percentage of polymer network is introduced, the mechanical strength of an LC system increases dramatically without significantly altering the electro-optic properties of the LC. One particular group of LCs, namely, ferroelectric liquid crystals (FLCs), are excellent candidates for such stabilization. FLCs, despite showing great potential for use in electro-optic and display technology due to inherently fast switching times and bistability, have found limited use as they are extremely susceptible to mechanical shock. This study examines the effects of polymerization conditions of a diacrylate monomer in an FLC on its inherent electro-optic properties. The LC phase in which polymerization occurs has a dramatic effect on the polymerization behavior and formation of the polymer network. Such effects have interesting implications on the ferroelectric polarization and switching speed of the FLC. As the temperature of polymerization increases and thus the order of the LC phase decreases, the ferroelectric polarization and the switching time increase.

Formation of Polymer Stabilized Ferroelectric Liquid Crystals using a Fluorinated Diacrylate

1999 ◽  
Vol 559 ◽  
Author(s):  
C. Allan Guymon ◽  
Christopher N. Bowman ◽  
Christopher N. Bowman
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Polymer Network ◽  
Isotropic Phase ◽  
Ferroelectric Liquid Crystals ◽  
Smectic C ◽  
Electro Optic ◽  
Polymerization Behavior ◽  
Mechanically Stabilized ◽  
Polymer Stabilized

ABSTRACTFerroelectric liquid crystals (FLCs) have shown great potential for use in electro-optic and display technology due to their inherently fast switching speeds and bistability. Recently, considerable research has been devoted to FLCs mechanically stabilized by a polymer network. The network is formed typically by in situ polymerization of a monomer dissolved in the FLC. Because of the inherent order in the FLC, the polymerization behavior may be significantly different than what might be expected in solution polymerizations. These deviations result largely from the segregation properties of the monomer in the liquid crystal. One class of monomers, namely fluorinated acrylates, is a likely candidate for inducing novel segregation, polymerization and electro-optic behavior in polymer stabilized ferroelectric liquid crystals (PSFLCs). The use of fluorinated moieties has a significant impact on the phase and polymerization behavior of liquid crystal systems. This study focuses on the polymerization of a fluorinated diacrylate, octafluoro 1,6-hexanediol diacrylate (FHDDA), to form PSFLCs and the consequent impact of the polymerization on the ultimate performance. Interestingly, as the temperature is increased and the order of the system decreases, a dramatic increase in the polymerization rate is observed. This increase is especially prominent for polymerizations in the smectic C* phase for which the rate is more than five times that exhibited at much higher temperatures in the isotropic phase. As with other monomer/FLC systems, the segregation of the monomer plays a role in this polymerization behavior as the monomer segregates between the smectic layers of the liquid crystal. The segregation properties also significantly impact the ultimate electro-optic properties. Both ferroelectric polarization and response time of the PSFLC change markedly with different polymerization temperatures, and approach values very close to those of the neat FLC under appropriate polymerization conditions. This behavior not only provides a unique mechanism for rate acceleration in PSFLCs, but also paves the way for new methods to optimize performance in these materials.

Studies of a Polymer Dispersed Ferroelectric Liquid Crystal

1995 ◽  
Vol 377 ◽  
Author(s):  
C. Allan Guymon ◽  
Erik N. Hoggan ◽  
Christopher N. Bowman
Keyword(s):  
Liquid Crystal ◽  
Polymer Network ◽  
Polymer Networks ◽  
Monomer Concentration ◽  
Fast Switching ◽  
Electro Optic ◽  
Phase Transition Temperatures ◽  
Polymer Dispersed ◽  
Display Technology ◽  
Rotational Viscosity

ABSTRACTFerrorlrtric liquid crystals (FLCs) have shown great potential for use in electro-optic and display technology due to theri inherently fast switching speeds. Recently within this area a great deal of attention has also been given to FLCs dispersed within a polymer networks. Adding the polymer may act to enhance certain electro-optic properties and will substantially increase the mechanical strenth on the FLC system. This study examines the effects of adding either a diacrylate monomer or a polymer network to a FLC mixture of known composition. The monomer depresses the phase transition temperatures to more orderd phases for both first and second order transitions and causes a marked decrease in the amount of liquid crystal which exhibits typical transitions behavior. During polymerization the network phase separates forming two cocontinuous phases and allows the liquid crystal transitions to return close to values seen in polymer systems. As a result of this decrease, the rotational viscosity decrease for these same samples. Maximum double bond conversions and polymerization rate maxima increase with monomer concentration until saturation on monomer in the liquid crystal is reached. The rate maxima then decreases as the monomer as the monomer must dissolute into the liquid crystal and diffuse to the reactive sites.

Analysis of Electro-Optic Properties of a Polymer Network Liquid Crystal Display with Crossed Polarizers

2007 ◽  
Vol 470 (1) ◽  
pp. 173-181 ◽  
Author(s):  
Sung-Ho Woo ◽  
Chan-Wook Jeon ◽  
Kee-Jeong Yang ◽  
Byeong-Dae Choi ◽  
Kumar Rajesh ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystal Display ◽  
Polymer Network ◽  
Electro Optic

scholarly journals Study of the vertically aligned in-plane switching liquid crystal mode in microscale periodic electric fields

2018 ◽  
Vol 9 ◽  
pp. 11-19 ◽  
Author(s):  
Artur R Geivandov ◽  
Mikhail I Barnik ◽  
Irina V Kasyanova ◽  
Serguei P Palto
Keyword(s):  
Liquid Crystal ◽  
Electric Fields ◽  
Grating Period ◽  
Surface Mode ◽  
Switching Speed ◽  
Electric Pulses ◽  
Display Technology ◽  
Vertically Aligned ◽  
New Applications ◽  
Micrometer Scale

The ongoing interest in fast liquid crystal (LC) modes stimulated by display technology and new applications has motivated us to study in detail the in-plane switching (IPS) vertically aligned (VA) mode. We have studied how the decrease of the period of the interdigitated electrodes (down to sub-micrometer scale) influences the switching speed, especially the LC relaxation to the initial homeotropic state. We have found that there are two types of the relaxation: a fast relaxation caused by the surface LC sub-layer deformed in the vicinity of the electrodes and the slower relaxation of the bulk LC. The speed of the fast (surface) mode is defined by half of a period of the electrode grating, while the relaxation time of the bulk depends on the LC layer thickness and the length of the driving electric pulses. Thus, the use of the surface mode and the reduction of the electrode grating period can result in significant increase of switching speed compared to the traditional LC modes, where the bulk relaxation dominates in electrooptical response. We have studied thoroughly the conditions defining the surface mode applicability. The numerical simulations are in good agreement with experimental measurements.

Electro-optic properties and wavelength effect in polymer network liquid crystal

1997 ◽  
Vol 33 (4) ◽  
pp. 565-569 ◽  
Author(s):  
Chi Hoon Choi ◽  
Seon Hee Kim ◽  
Eun Young Hong ◽  
Byung Kyu Kim
Keyword(s):  
Liquid Crystal ◽  
Polymer Network ◽  
Electro Optic

Electro-optic effect, propagation loss, and switching speed in polymers containing nano-sized droplets of liquid crystal

2000 ◽  
Vol 27 (5) ◽  
pp. 649-655 ◽  
Author(s):  
Shiro Matsumoto ◽  
Yasuyuki Sugiyama ◽  
Seizou Sakata ◽  
Takayoshi Hayashi
Keyword(s):  
Liquid Crystal ◽  
Propagation Loss ◽  
Switching Speed ◽  
Electro Optic

Anomalously Large Bend Elastic Constant and Faster Electro-Optic Response in Soft Glassy Gels Formed by a Dipeptide

2011 ◽  
Vol 181-182 ◽  
pp. 14-21 ◽  
Author(s):  
Geetha G. Nair ◽  
R. Bhargavi
Keyword(s):  
Liquid Crystal ◽  
Elastic Constant ◽  
Nematic Liquid Crystal ◽  
Surprising Result ◽  
Switching Speed ◽  
Electro Optic ◽  
Thermoreversible Gels ◽  
Order Of Magnitude

In this article, results of static/dynamic Freedericksz transformation and rheological studies on anisotropic thermoreversible gels formed by gelation of a nematic liquid crystal (NLC) with a monodisperse dipeptide are presented. Freedericksz transformation studies reveal a surprising result: the gel state possesses a very large Frank bend elastic constant value, order of magnitude higher than the sol state, whereas, the splay elastic constant shows relatively a small increase. The studies also demonstrate that the anisotropic gel to anisotropic sol transition can be tracked by simply monitoring the Freedericksz transformation. Other attractive features of the gel state include the vanishing of the undesirable backflow effect, and nearly an order of magnitude decrease of switching speed. Further, rheological studies bring out the soft glassy characteristics of these gels.

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