Response Of Polymer Dispersed Liquid Crystals Research Articles

Electro-optical response of polymer-dispersed liquid crystals doped with γ-Fe2O3 nanoparticles

ABSTRACT In this paper, the microstructures of the dilute magnetic PDLC films, doped with low concentrations of γ-Fe2O3 nanoparticles, have hardly changed, but their electric-optical responses have distinctly changed. The experimental results show that the threshold voltage and hysteresis decreased with the increasing concentration of γ-Fe2O3 nanoparticles. Furthermore, at the relatively low concentration of γ-Fe2O3 nanoparticles (samples (0) and (1) according to ϕm of 0 and 0.11%), the reciprocity of the rise time increased nonlinearly with the increasing square of the applied voltage. However, at the relatively high concentration of γ-Fe2O3 nanoparticles (samples (2) according to ϕm = 0.15%), the reciprocity of the rise time increased linearly with the square of the applied voltage. Moreover, the reciprocity of the decay time was independent of the applied voltage and decreased with increasing the concentration of γ-Fe2O3 nanoparticles. These characteristics are due to the adsorption of free ions by γ-Fe2O3 nanoparticles. As a result, the interfacial interaction between liquid crystal droplets and the polymer matrix decreased, and the effective electric field inside the liquid crystal droplets increased.

Thermally responsive polymer-dispersed liquid crystal diffusers fabricated using laser speckle pattern irradiation

This study examined the thermal response of polymer-dispersed liquid crystal (PDLC) diffusers, patterned using a two-lens imaging system. Optical modulation was achieved by modifying the PDLC transmittance using temperature-induced changes to liquid crystal (LC) orientation. PDLCs with controllable scattering properties were obtained by irradiating LC-polymer composites with laser speckle patterns. The variation of the scattering characteristics of the PDLCs with temperature, average speckle size, and LC orientation order was analyzed to determine the most suitable parameters for a diffuser for smart window solar-ray control applications. The findings of these experiments demonstrate that using speckle patterns, a one-time laser exposure process, can provide a simple fabrication method of novel optical devices.

Electro-optical response of polymer-dispersed liquid crystal single layers of large nematic droplets oriented by rubbed teflon nanolayers

The surface orienting effect of rubbed teflon nanolayers on the morphology and electro-optical (EO) response of polymer-dispersed liquid crystal (PDLC) single layers of large nematic droplets was studied experimentally. In PDLC composites of the nematic liquid crystal (LC) E7 and NOA65 polymer, single droplets of LC with diameters as larger as 10 μm were confined in layers with a thickness of 10 μm, and the nematic director field was efficiently modified by nanostructuring teflon rubbing of the glass plates of the PDLC cell. For layered PDLCs arranged and oriented in this way, the modulated EO response by the dielectric oscillations of the nematic director exhibits a selective amplitude-frequency modulation controllable by both temperature and voltage applied, and is simply related to the LC droplet size. That may be of practical interest for PDLC-based modulators operating in the infrasound frequency range.

The Effect of Dual-Frequency Addressing on the Electro-Optic Response of a PDLC Film

Abstract The effect of using dual-frequency addressing in the reduction of the response time in polymer dispersed liquid crystal (PDLC) displays has been investigated. The utilization of a second high frequency component of the driving voltage enables an added control of the waveform not possible in a single frequency addressed system. The use of dual-frequency addressing, combined with some special driving techniques, opens up the possibility of controlling the response of PDLC displays in sweeping-mode operations.