RESEARCH PAPER Comparison of Guest–Host Liquid Crystal Systems Doped with Azo or Anthraquinone Dyes Meryem Gu ¨rlu ¨k 1 • Hilal Altindis ¸ Abdulkadir 1 • Meryem Sena Akkus ¸ 1 • Fatih Akkurt 2 • Ahmet Alicilar 1 Received: 2 April 2014 / Accepted: 18 June 2016 Ó Shiraz University 2017 Abstract Importance of liquid crystals used in display technology has been rapidly increased by technological developments in recent years. Guest–host liquid crystal displays (GH-LCDs) are widely utilized because of their many advantages such as color, wide viewing angle and high brightness. In this experimental work, azo and anthraquinone, two differently structured dies (Disperse Orange11 and 13), were separately doped to two different nematic liquid crystals (E63 and ZLI-1132). Their solu- bilities, order parameters, textures and phase transition temperatures were determined. The highest solubility value was attained with Orange 13 dye in ZLI-1132 while the highest order parameter was obtained with Orange 11 dye in E-63. These dyes did not significantly destabilize the mesomorphic phase of nematic hosts. It was also observed that any narrowing on the temperature range of the liquid crystals had not taken place with the addition of dopants to the crystal, on the contrary, an increase was recorded. Keywords Nematic liquid crystal  Dye  Order parameter  Dichroic ratio  Guest–host systems 1 Introduction If dichroic dyes are dissolved as guest species in liquid crystalline media, they align with their long axes in a specified direction determined by the ordered arrangement of the liquid crystal molecules. This phenomenon is called the ‘‘guest–host’’ effect (Bauman and Moryson 1997). Guest–Host displays have attracted much attention because of their wide viewing angle, excellent hues and high brightness levels. To realize bright and pure colors in these displays, the dyes having suitable characteristics must be used (Alicilar et al. 2010). In a guest–host liquid crystal display (GH-LCD), a dichroic dye (guest) is dissolved in a liquid crystalline host which acts as an anisotropic matrix to orientate the dye molecules. An electrical field applied to the display reorients the liquid crystal and dye molecules along the field direction, and induces a change in the selective absorption of the dichroic dye (Akman et al. 2014). Liquid crystalline materials are the specific fluids which possess partial molecular orientational and positional ordering, but do not have the full translational symmetry as solid crystals (Giziroglu et al. 2014). LCs are non- linear optical materials, and their various properties investigated so far have revealed the promising charac- ters of these materials. Employing nematic LC between transparent electrodes is the fundamental technique for producing spatial light modulators that are widely used and are important in various adaptive optics and image/ signal processing systems (Khoo et al. 1999). Further- more, to obtain materials with eutectic physical proper- ties for displays or other optical devices, dyes may be doped in liquid crystalline materials (Ivashchenko 1994; Bauman and Moryson 1997; Iwanaga et al. 2000; Ruzak et al. 2003; Lin and Fuh 2009 Rahman et al. 2010; Budagovsky et al. 2016; Maleki et al. 2016). Some properties of dichroic dyes, especially their absorption spectra, solubility and dichroic ratios, are important for the realization of high performances. For this purpose, the dyes in different chemical structures, & Fatih Akkurt fatih@boren.gov.tr 1 Chemical Engineering Department, Gazi University, Maltepe, 06570 Ankara, Turkey 2 National Boron Research Institute, C ¸ ankaya, 06520 Ankara, Turkey 123 Iran J Sci Technol Trans Sci DOI 10.1007/s40995-017-0186-0