Polymer Dispersed Ferroelectric Liquid Crystal Research Articles

Biowaste-based porous carbon nanoparticle doped polymer dispersed ferroelectric liquid crystal composites: an impact on optical and electrical properties

Bio-waste-based porous carbon nanoparticles (PCNPs) were synthesized using green synthesis and investigated their doping effect on the optical and electrical properties of polymer-dispersed ferroelectric liquid crystals (PDFLCs) composites. Here we employed the polymerization-induced phase separation (PIPS) approach for constructing the PDFLCs. Our results indicate that the dispersion of PCNPs into the PDFLC material results in an alteration to several physical parameters, including morphology, dielectric permittivity, conductivity and optical band gap. A decrease in the ac conductivity of the doped samples was seen. Additionally, UV-Visible study reveals that inclusion of PCNPs resulted in a decrease in the optical band gap of PDFLC, with a value of approximately 3.1 eV. These findings demonstrate the potential of using PCNPs as dopants in PDFLCs for various applications, including sensing, energy storage and optoelectronics.

Synthesis and characterization of biowaste-based porous carbon nanoparticle-polymer dispersed ferroelectric liquid crystal composites

Herein, porous carbon nanoparticles (PCNPs) were synthesized using magnolia champaca seed pods and studied their doping effect on the polymer-dispersed ferroelectric liquid crystal (PDFLC) properties. The effect of PCNPs concentration (≤0.75 wt.%) on the morphology of PDFLC, polarization, and permittivity are investigated in thin sample cells. Field emission scanning electron microscope image results indicate the spherical shape of PCNPs of particle size ∼27 nm diameter. Temperature-dependent electro-optic and dielectric properties are also investigated in the wide SmC* phase and near transition temperature of SmC*-SmA*. Polarising optical microscope textures confirm the non-homogeneity of FLC molecules in the polymer matrix as a function of PCNPs concentration. Thespontaneous polarization and anchoring energy coefficients increase with increasing the doping amount of PCNPs.The phase transition temperature is found unaffected by PCNP doping in all prepared samples. In PDFLC and PCNPs doped PDFLC composites, usualbehaviourof permittivity as a function of temperature is observed. Fluorescence spectra show an enhanced two-fold increase in emission intensity peak at 412 nm wavelength for 0.5 wt.% PCNPs doped PDFLC while concentration-dependent quenching and slight redshift have been observed for the 0.75 wt.% PCNPs doped PDFLC. The enhanced electro-optic and dielectric properties observed in the composites suggest potential applications in displays, sensors, and optical devices. The findings open doors for further exploration and utilization of these functional materials in advanced electronic and photonic technologies.

Effect of ZnO nanoparticles on the morphology, dielectric, electro-optic and photo luminescence properties of a confined ferroelectric liquid crystal material

The influence of spherical zinc oxide nanoparticles (ZnO-NPs) incorporated in low concentrations (0.45, 0.7, 1.0wt/wt%) into a polymer confined ferroelectric liquid crystal (FLC) has been investigated. Varying the concentration of ZnO-NPs is found to have a profound impact on the morphology of the polymer dispersed ferroelectric liquid crystal (PDFLC) composites. With increasing ZnO-NP content, the real and imaginary parts of the permittivity and the dielectric strength of a relevant relaxation mode depict an increase. However, the associated relaxation frequency shifts to lower values; a concomitant increase in spontaneous polarization is also observed. The response time of the composites slightly improved on doping with the ZnO-NPs. The changes in electro-optic and dielectric parameters are explained in terms of change in elastic energy as well as surface morphology of the composites. Interestingly, the polymer/liquid crystal environment is also seen to enhance the photoluminescence response of confined FLC.

Impact of dye on the switching responses of polymer dispersed ferroelectric liquid crystal

ABSTRACTPolymer dispersed ferroelectric liquid crystals (PDFLCs) have disclosed an enormous approach for use in electro-optic and display technology since ferroelectric liquid crystals (FLCs) have inherently fast switching speeds. In this work, we equipped dichroic PDFLC using dye-doped chiral SmC* liquid crystal (LC) and ultra-violet (UV) curable polymer by polymerization induced phase separation (PIPS) method. All fundamental material aspects like optical transmissions, spontaneous polarization, threshold voltage, contrast ratio and response time as a function of applied voltage, temperature, and dye concentration were examined. In the electro-optic study, 82% transmission with a threshold field value ∼0.6 V/μm was observed for PDFLC, however, 90% transmission was achieved with a threshold field ∼0.3 V/μm at the dye concentration of 0.125% (wt./wt.). As a result, present dichroic PDFLC device shows microseconds switching response, higher polarization value and superior contrast, at low dye concentration.

Effect of polymer concentration on morphology, dielectric and optical properties in a polymer-dispersed ferroelectric liquid crystal

ABSTRACTPhotocurable polymer-dispersed ferroelectric liquid crystal were prepared by polymerisation-induced phase separation (PIPS). Morphological behaviour was analysed by polarising optical microscopy (POM) and scanning electron microscopy (SEM). FLC droplet size was found in the range of ~ 2–70 µm and decreases with an increase in polymer content. Relaxation frequency, dielectric strength and ac conductivity were evaluated as a function of polymer concentration and it was concluded that the polymer concentration has a significant effect on these parameters. The energy band gap () increases with polymer concentration and was found in the range of ~ 3.3 eV at higher concentration of polymer.

Effects of polymer viscosity on the polymerization switching and electro-optical properties of unaligned liquid crystal/UV curable polymer composites

Polymer dispersed ferroelectric liquid crystal composite films consisting of varying polymer viscosities were prepared by polymerization induced phase separation (PIPS) technique. It was found that polymer viscosity influences the polarization switching and optical responses. A polymer dispersed ferroelectric liquid crystal film of low polymer viscosity shows faster switching, however a higher optical transmission at ~ 70% was observed in a higher polymer viscosity film.

Phase Modulation of Light by a Composite Film with Fine Ferroelectric Liquid Crystal Droplets: Theoretical Treatment

To describe phase and intensity modulation of the plane wave transmitted through a polymer dispersed ferroelectric liquid crystal (PDFLC) film with nanosized liquid crystal (LC) droplets the model based on the Foldy-Twersky and anisotropic dipole approximations is proposed. The dependence of phase shift and transmittance of films with fine droplets on their properties has been elucidated. The films with polarization-independent phase shift at switching of cylindrically symmetric structure of bistable smectic LC droplet director are investigated.

Holographic diffraction gratings using polymer-dispersed ferroelectric liquid crystals

By controlling the morphology of holographic polymer-dispersed ferroelectric liquid crystals (FLCs), highly aligned FLC domains are obtained for diffractive optical applications. Rapid, thresholdless switching is observed for various grating pitch sizes between approximately 3 and approximately 12 microm. A simple phenomenological model is presented encompassing a distribution of domain sizes and an effective field that stabilizes the FLC domains to reflect the observed thresholdless switching and optical behavior.

Physical mechanism for in-plane molecular orientation in polymer-dispersed ferroelectric liquid crystals

The physical mechanism of liquid crystal (LC) alignment in ferroelectric LC (FLC) droplets dispersed in a photocurable polymer matrix was studied. The orientational ordering of both FLC molecules and the polymer matrix was induced by a rubbed polyimide alignment layer. There existed an optimum FLC droplet size for the production of uniformly oriented molecules and smectic layers for maximum electro-optic modulation. The alignment quality was critically dependent on the droplet size, shape, the helical pitch, and the phase transition sequence of the FLCs. The molecular structure formed inside the FLC droplets resulted from a delicate balance between the elastic energy stored in a restricted geometry and surface interactions at the FLC-polymer interface.

The Electro-Optical Property of Guest-Host PDFLC Film Containing Anthraquinone Dye

ABSTRACT This paper focuses on the light transmission properties of Dye Guest-Host Polymer Dispersed Ferroelectric Liquid Crystal (DGHPDFLC). The DGHPDFLC samples were prepared by using various concentrations of UV curable polymer and 3 wt% blue dichroic dye under various intensities of ultraviolet irradiation. This system can remove a polarizer to achieve better brightness, and improve the transmission of Dye Guest-Host Ferroelectric Liquid Crystal and Polymer Dispersed Ferroelectric Liquid Crystal systems. The results show that the addition of polymer increases the ratio of transmitted light. The prepolymer (NOA65) become fully cured at a higher UV irradiation intensity, and it decreases the transmission of the system.

Electro-optic properties of aligned polysiloxane dispersed ferroelectric liquid crystal composite thin films

Abstract Thin polymer dispersed ferroelectric liquid crystal (PDFLC) composite films were prepared using polydimethyl siloxanes of different viscosity grades and ferroelectric liquid crystal mixture (ZLI-3654) using solvent induced phase separation (SIPS) and polymer induced phase separation (PIPS) techniques simultaneously. The electro-optic properties of these films in aligned and unaligned configurations were measured. A comparison indicates that the performance of aligned PDFLCs is better over that of the unaligned films. Structure–property correlation in these materials have been studied and explained on the basis of the viscosity of the polysiloxane matrix. These materials are found to be promising for flexible liquid crystal display devices.

Effect of polymer viscosity on morphological and electro-optic properties of aligned polymer dispersed ferroelectric liquid crystal composite films

A room temperature ferroelectric liquid crystal mixture was dispersed in UV curable polymers of different viscosity in 30:70 wt/wt ratio. These polymer dispersed ferroelectric liquid crystal (PDFLC) composite films were prepared by polymerization induced phase separation technique. It was found that the polymer viscosity influences the droplet size and the electro-optic properties. The spontaneous polarization of PDFLC decreases with an increase in polymer viscosity. The droplet morphology and electro-optic properties of these materials have been investigated in an aligned configuration.

Comparative analysis of basic physical properties of a ferroelectric liquid crystal and a polymer dispersed ferroelectric liquid crystal

A polymer film of polyvinylbutyral with dispersed droplets of a ferroelectric liquid crystalline mixture (FLC309c) has been prepared and characterized. The collective processes have been studied by dielectric relaxation spectroscopy in the frequency range 10 Hz to 13 MHz. In comparison with the FLC309c mixture, the polymer dispersed ferroelectric liquid crystal (PDFLC309c) based on FLC309c exhibits a Goldstone-like mode relaxation with a much higher relaxation frequency, but a smaller dielectric strength than the Goldstone mode observed for the FLC309c mixture. The spontaneous polarization of PDFLC309c decreases by nearly one order of magnitude in comparison with FLC309c, while the tilt angle decreases by 20%. Considering these results, we believe that a non-switching region exists near the polymer boundaries and that significant deformations of the helical structure occur due to stronger anchoring.

Polymer dispersed ferroelectric liquid crystal films with high electro-optic quality

Polymer dispersed ferroelectric liquid crystal (PDFLC) films are composite materials of a ferroelectric liquid crystal dispersed in the form of micron-sized droplets in a polymer matrix. In this study PDFLC films with a novel ferroelectric mixture were prepared by a polymerization-induced phase separation technique. The uniform orientation of the ferroelectric liquid crystal droplets was obtained by shearing during the phase separation process. The electro-optic characteristics of the films were analysed. Experimental results on response times, contrast ratio and spontaneous polarization were presented. Since these films exhibit high electro-optic quality, they have the potential of use in a wide range of display devices.

Effects of the Anthraquinone Dye on the Electro-Optical Properties of Dye Guest-Host Polymer Dispersed Ferroelectric Liquid Crystal

The effects of the anthraquinone dye on the electro-optical characteristics of DGHPDFLC have been investigated. The results show that PDFLC doped with dichroic dye was found to have no influence on phase separation. When dye concentration is over M483-1.0%, it causes the response time of DGHPDFLC to become slower, the frequency becomes dependent, the rotational viscosity increases, and the tilt angle becomes lower, but, on the whole, electro-optical properties are still very practical.

POLARIZATION STUDIES ON STRETCHED POLYMER DISPERSED FERROELECTRIC LIQUID CRYSTAL FILMS

We obtained polymer dispersed ferroelectric liquid crystal films using a new ferroelectric liquid crystal code name S9MHL and PMMA. The elongation of the liquid crystal droplets appeared, caused by hot stretching and pressing the films. We studied the dependence of the polarization upon temperature, frequency and amplitude of the applied electric field for different liquid crystal concentrations. The highest switching time in the range of tens of microseconds has been reached.

Light modulation characteristics of a single-polarizer electro-optical cell based on polymer dispersed ferroelectric liquid crystals

Features of the light passing through a single-polarizer electro-optical cell based on a uniaxially oriented film of a polymer dispersed ferroelectric liquid crystal have been studied. The optical response as a function of the applied electric field is shown to depend on the cell geometry. A detailed analysis is presented of the dependence of the maximum light transmission, modulation depth and contrast ratio on the angle between the light polarization and the film orientation direction, on its optical anisotropy and on the molecular tilt angle. An approximate formula is proposed to estimate the highest attainable contrast. Parameters under study have been measured for PDFLC films varying in optical anisotropy value. The experimental results prove to be in good agreement with theoretical estimations.

Coherent transmittance quenching effect in thin films of polymer-dispersed ferroelectric liquid crystals

The conditions for vanishing of the coherent component of radiation transmitted through a monolayer of polymer-dispersed ferroelectric liquid-crystal droplets are found. The influence of polydispersity and disorientation of axes of semispherical droplets on the conditions of interference quenching is studied. It is shown that these factors cause a change in the average size and concentration of droplets for which the quenching effect is realized. Data on the contrast ratio and the modulation depth of a monolayer, determined from the coherent component of transmitted radiation, are presented. It is shown that these characteristics can be considerably improved under quenching conditions for a film of polymer-dispersed ferroelectric liquid-crystal droplets.

Saturation voltage and elastic energy of polymer dispersed ferroelectric liquid crystal films

The reduction of the elastic energy of Polymer Dispersed Ferroelectric Liquid Crystal (PDFLC) films results in a decreasing of the saturation voltage. The size and shape of the droplets determine the PDFLC electrooptical effect and the temperature dependence of the saturation voltage. PDFLC films with the saturation voltage of 7–9 V have been created.

Spontaneous polarization and response time of polymer dispersed ferroelectric liquid crystal (PDFLC)

Results reported on the spontaneous polarization, switching time and rotational viscosity measurement of a FLC compound in neat phase and that in polymer matrix in the present paper. Polymer-dispersed ferroelectric liquid crystal film was formed by photopolymerization due to polymerization induced phase separation. A detailed study has been made on the spontaneous polarization, switching time at different temperatures and measuring field. It has been observed that the magnitude of spontaneous polarization of the PDFLC mixture is not in accordance with their mixing ratio. The switching time in PDFLC mixture is less than that in neat FLC mixture.