Stanislaw J. Klosowicz

Optics and electro-optics of polymer-dispersed liquid crystals: physics, technology, and application

A brief description of the basic optical and electro-optical effects observed in polymer-dispersed liquid crystals (PDLCs) is presented. Theoretical models of light scattering from such structures and measurement techniques of PDLC optical properties are included, based on which of the material properties of polymer and liquid crystal required for application are discussed. Special attention is paid to the methods for optimizing PDLC optical and electro-optical properties. Finally, the known and possible applications of PDLC optical properties are discussed.

Progress in Studies on the Effect of Ionizing Radiation on the Physical Properties of Cholesteric Liquid Crystals

Abstract An overview of the present knowledge about the effect of ionizing radiation on properties of cholesteric liquid crystals is given. It includes the effects caused by either electromagnetic radiation or particles. Particular attention has been paid to the liquid-crystalline properties of cholesterol derivatives and their mixtures including non-mesogenic dopants. Some of the results are published for the first time.

Influence of Fluorine Substitution for Hydrogen on the Appearance of SmC* Phase Between SmA* and SmCa* Phases

Recently several fluorinated molecules have been investigated by many means [1]. We investigated in details physical properties of two antiferroelectric liquid crystals [2]: MHPB(H)PBC and MHPB(F)PBC. In MHPB(H)PBC paraelectric SmA∗ phase neighbours antiferroelectric SmCA∗ phase, while in MHPB(F)PBC the substitution of fluorine for hydrogen leads to formation of additional narrow ferroelectric phase SmC∗ phase, placed between the mentioned above phases. We also found several other phenomena, namely: increasing of the phase transition temperatures for fluorinated compound in comparison with hydrogenated one, decreasing of the smectic layer thickness, and increasing of spontaneous polarisation. In our work we focused on the explanation of these phenomena from the molecular point of view using computer molecular modelling.

Switching of orthoconic antiferroelectric mixtures in PDLC system

Polymer-dispersed liquid crystals containing orthoconic antiferroelectric smectics were prepared by photopolymerization-induced phase separation. Mean droplet size allowed formation of antiferroelectric helix inside droplets. Bias electric field applied during phase separation aligned helical axes parallel to the cell plane. Obtained ellipsoidal droplets were optically uniaxial for perpendicular light beam. The cells were switched by square or triangle driving signal unwinding the helix. V-shape switching was found instead of threshold one observed in conventional cells of the same mixture. The switching time was crucially depended on temperature. Those effects were caused by anchoring conditions inside polymer cavities.

Tunable Liquid Crystal Fiber-Optic Polarizer and Related Elements

Abstract A new in-line type tunable liquid crystal fiber-optic device is presented. The main idea is to obtain anisotropic waveguide structure based on biconically tapered isotropic fiber core and anisotropic liquid fiber clad. As the liquid-crystalline clad, the nematic mixture 1110-10C3 made by Dabrowskis group has been used. The special construction of a device with square cross-section secures a possibility to change molecular orientation of the liquid-crystalline clad by external field. Thus, different polarising action has been obtained depending on fulfilment waveguide condition of the structure.

Polymer-dispersed ferroelectric and antiferroelectric liquid crystals

Abstract PDLC structures containing ferroelectric and antiferroelectric liquid crystal phase of the same material have been obtained. The initial studies of electrooptical properties of those materials have been done.

PDLC diffraction grating

A permanent periodic structural grating has been formed in a PDLC layer. This structural pattern caused a diffraction of the incident light. The obtained structure has exhibited features of both amplitude and phase diffraction grating. Due to PDLC electro-optical properties, this grating is adjustable by electric field i.e., the grating type and the diffraction fringe number depends on applied field.

A Simple Method to Prepare Polymer Dispersed Liquid Crystals

Abstract A simple method of dispersing nematics in poly (vinyl alcohol) and other polymers is presented. This method may be used for fundamental studies of different dispersed nematic materials.

Optical Effects in Polymer-Dispersed Liquid Crystal - Fibre Optic Devices

Abstract Optical effects in PDLC - fibre optic systems have been studied. The main attention is devoted to intensity modulation based upon electrically driven transmittance and switching effects based upon grating structures in PDLC films. Obtained results are discussed from application point of view.

How to Choose the Proper Polymer to PDLC Prepare

Abstract Polymer dispersed liquid crystals exhibit some advantages in applications and also interesting physical properties. In this contribution we present general rules of choosing a proper polymer, which fulfill all basic requirements, for PDLC preparation.