Browsing by Author "Karapinar, R."

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Electro-Optic Response of a Polymer Dispersed Liquid Crystal Film
(1998) Karapinar, R.
Polymer dispersed liquid crystal (PDLC) films are potentially useful in electrooptic devices since they can be used for vision products. In this work the PDLC thin films were prepared by a photopolymerization induced phase separation method and electro-optic properties of the films were investigated.
Light Scattering Measurements in Nematic Liquid Crystals Ii. Spectral Analysis of Laser Light Intensity Fluctuations in the Nematic Liquid Crystal, 8cb
(TUBITAK, 1996) Karapinar, R.; Gündüz, E.
We present a study of the spectral analysis of light scattered by director fluctuations in a nematic liquid crystal (8CB). From the experimental measurements, we obtain damping times of the twist-type director fluctuations by studying the noise intensity spectrum of scattered laser light.
Liquid Crystalline Materials for Spatial Light Modulation
(2001) Lucchetti, L.; Lucchetta, D.E.; Karapinar, R.; Manni, A.; Simoni, F.
The liquid crystalline materials for spatial light modulation were discussed. Nano-sized polymer dispersed liquid crystals (PDLCS) were found to be obtained using a mixture of the monomer dipentaerythrol hydoxy penta acrylate (DPHPA), the photoinitiator benzophenone (BP), the stabilizer N-vinyllpyrrollidone (NVP) and the nematic liquid crystal E7. The analysis suggested the use of liquid crystalline materials for obtaining transparent nano-PDLCs with a polarization-independent electro-optical response.
Measurement of Electro-Optical Parameters of a High Contrast Flc Film
(Elsevier, 2009) Karapinar, R.; O'Neill, M.; Hird, M.
We have fabricated a ferroelectric liquid crystal (FLC) film by using a novel ferroelectric mixture. The various ferroelectric parameters such as response time, spontaneous polarization and contrast ratio of the FLC film have been measured. Experimental results show that the FLC film exhibits high contrast ratios and fast optical response. The FLC film has a possibility of the use in display applications because of the performance characteristics. (C) 2008 Elsevier B.V. All rights reserved.
Nano-Colloids of Sn2p2s6 in Nematic Liquid Crystal Pentyl-Cianobiphenile
(inst Condensed Matter Physics Natl Acad Sciences Ukraine, 2010) Kurochkin, O.; Atkuri, H.; Buchnev, O.; Glushchenko, A.; Grabar, O.; Karapinar, R.; Reznikov, Yu.
It has been shown experimentally that the ferroelectric nano-particles, in common with other molecular additives, shift the clearing temperature, T-c, extending or reducing the two-phase coexistent region and changing the average order parameter of the single-component nematics. An increase of up to 11 degrees C or a smaller decrease of as much as 3 degrees C of T-c, and corresponding changes of the order parameter were observed In all cases the order parameter of the colloid followed the universal temperature behaviour, which is a characteristic of LCs with molecular additives
New Coumarin Polymers as Non-Contact Alignment Layers for Liquid Crystals
(Taylor and Francis Inc., 1999) Hindmarsh, P.; Owen, G.J.; Kelly, S.M.; Jackson, P.O.; O'Neill, M.; Karapinar, R.
The synthesis of polymethacrylate derivatives of 6- and 7-hydroxycoumarin is described and their use as photoinduced alignment layers for liquid crystals is discussed. Strong anchoring is found with azimuthal anchoring energies > 6.9 × 10-5 J m-2. The liquid crystal alignment direction is parallel to the polarisation direction of the incident UV light when low fluences are incident. At a critical fluence threshold, a sharp change to perpendicular alignment is found. The incorporation of a flexible spacer into the coumarin sidechain results in stronger anchoring at low fluences. These results are discussed in terms of a molecular model.
Switching Process in a Surface-Stabilized Ferroelectric Liquid Crystal Film
(2000) Karapinar, R.
In this paper we first discuss the operating principle of a ferroelectric liquid crystal film in the surface stabilized configuration, and then examine the switching characteristics using optical measurements performed with a polarizing microscope.