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.

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.

scholarly journals Holographic Polymer-Dispersed Liquid Crystals: Materials, Formation, and Applications

2008 ◽  
Vol 2008 ◽  
pp. 1-52 ◽  
Author(s):  
Y. J. Liu ◽  
X. W. Sun
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Refractive Index Profile ◽  
Single Step ◽  
Fast Switching ◽  
Polymer Dispersed Liquid Crystal ◽  
Current State ◽  
Index Matching ◽  
Polymer Dispersed ◽  
Materials Used

By combining polymer-dispersed liquid crystal (PDLC) and holography, holographic PDLC (H-PDLC) has emerged as a new composite material for switchable or tunable optical devices. Generally, H-PDLC structures are created in a liquid crystal cell filled with polymer-dispersed liquid crystal materials by recording the interference pattern generated by two or more coherent laser beams which is a fast and single-step fabrication. With a relatively ideal phase separation between liquid crystals and polymers, periodic refractive index profile is formed in the cell and thus light can be diffracted. Under a suitable electric field, the light diffraction behavior disappears due to the index matching between liquid crystals and polymers. H-PDLCs show a fast switching time due to the small size of the liquid crystal droplets. So far, H-PDLCs have been applied in many promising applications in photonics, such as flat panel displays, switchable gratings, switchable lasers, switchable microlenses, and switchable photonic crystals. In this paper, we review the current state-of-the-art of H-PDLCs including the materials used to date, the grating formation dynamics and simulations, the optimization of electro-optical properties, the photonic applications, and the issues existed in H-PDLCs.

scholarly journals High-Performance Polymer Dispersed Liquid Crystal Enabled by Uniquely Designed Acrylate Monomer

Polymers ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 1625 ◽  
Author(s):  
Rijeesh Kizhakidathazhath ◽  
Hiroya Nishikawa ◽  
Yasushi Okumura ◽  
Hiroki Higuchi ◽  
Hirotsugu Kikuchi
Keyword(s):  
Optical Properties ◽  
Liquid Crystal ◽  
Low Voltage ◽  
Polymer Networks ◽  
Mesh Size ◽  
Laser Scanning Microscopy ◽  
Present System ◽  
Driving Voltage ◽  
Acrylate Monomer ◽  
Polymer Dispersed

The widespread electro–optical applications of polymer dispersed liquid crystals (PDLCs) are hampered by their high-driving voltage. Attempts to fabricate PDLC devices with low driving voltage sacrifice other desirable features of PDLCs. There is thus a clear need to develop a method to reduce the driving voltage without diminishing other revolutionary features of PDLCs. Herein, we report a low-voltage driven PDLC system achieved through an elegantly simple and uniquely designed acrylate monomer (A3DA) featuring a benzene moiety with a dodecyl terminal chain. The PDLC films were fabricated by the photopolymerization of mono- and di-functional acrylate monomers (19.2 wt%) mixed in a nematic liquid crystal E7 (80 wt%). The PDLC film with A3DA exhibited an abrupt decline of driving voltage by 75% (0.55 V/μm) with a high contrast ratio (16.82) while maintaining other electro–optical properties almost the same as the reference cell. The response time was adjusted to satisfactory by tuning the monomer concentration while maintaining the voltage significantly low (3 ms for a voltage of 0.98 V/μm). Confocal laser scanning microscopy confirmed the polyhedral foam texture morphology with an average mesh size of approximately 2.6 μm, which is less in comparison with the mesh size of reference PDLC (3.4 μm), yet the A3DA-PDLC showed low switching voltage. Thus, the promoted electro–optical properties are believed to be originated from the unique polymer networks formed by A3DA and its weak anchoring behavior on LCs. The present system with such a huge reduction in driving voltage and enhanced electro–optical performance opens up an excellent way for abundant perspective applications of PDLCs.

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 Reverse switching of surface roughness in a self-organized polydomain liquid crystal coating

2015 ◽  
Vol 112 (13) ◽  
pp. 3880-3885 ◽  
Author(s):  
Danqing Liu ◽  
Ling Liu ◽  
Patrick R. Onck ◽  
Dirk J. Broer
Keyword(s):  
Surface Roughness ◽  
Liquid Crystal ◽  
Nematic Liquid Crystal ◽  
Light Exposure ◽  
Polymer Network ◽  
Polymer Networks ◽  
Domain Size ◽  
Interference Microscopy ◽  
Light Illumination ◽  
Modulation Amplitude

In this work we propose randomly ordered polydomain nematic liquid crystal polymer networks to reversibly generate notable jagged relief patterns at a polymer coating surface by light illumination. The domain size is controlled by the addition of traces of partly insoluble fluorinated acrylate. The photoresponse of the coating is induced by a small amount of copolymerized azobenzene monomers. Upon exposure to UV light, azobenzene undergoes trans to cis isomerization, resulting in a change in molecular order and packing within each domain. The extent of this effect and its directionality depends on the domain orientation. Localized to domain level, this morphological change forms large 3D spikes at the surface with a modulation amplitude of more than 20% of the initial thickness. The process is reversible; the surface topographical patterns erase within 10 s by stopping the light exposure. A finite element model is applied to simulate the surface topography changes of the polydomain coating. The simulations describe the formation of the topographic features in terms of light absorption and isomerization process as a function of the director orientation. The random director distribution leads to surface structures which were found to be in close agreement with the ones measured by interference microscopy. The effect of domain size on surface roughness and depth modulation was explored and related to the internal mechanical constraints. The use of nematic liquid crystal polydomains confined in a polymer network largely simplifies the fabrication of smart coatings with a prominent triggered topographic response.

Electro-Optic Effects in Nanophase Polymer Dispersed Liquid-Crystal Systems

1997 ◽  
Vol 488 ◽  
Author(s):  
R. S. Blacker ◽  
K. L. Lewis ◽  
I. Mason ◽  
I. Sage ◽  
K. Webb
Keyword(s):  
Refractive Index ◽  
Composite Material ◽  
Liquid Crystal ◽  
Spectral Band ◽  
Essential Difference ◽  
New Class ◽  
Polymer Dispersed Liquid Crystal ◽  
Electro Optic ◽  
Polymer Dispersed ◽  
Polymeric Host

AbstractResearch into electro-optic effects in nanophase polymer dispersed liquid crystal (PDLC) materials has highlighted their potential as materials for a new class of tuneable filters. The structures, based on UV cured phase separated composites, contain liquid crystal both as discrete nano-scale droplets, and as material dissolved in the polymeric host. The essential difference between these materials and more conventional PDLC's is the scale of the refractive index inhomogeneity which is considerably smaller than the wavelength of visible light. Based upon effective medium approximations, the composite thus acts as a single isotropic medium, whose average refractive index is dependant on the level of applied electric field. Tuneable filters have been fabricated using the composite material for use in the visible spectral band.

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