Syntheses and Properties of New Smectic Reactive Mesogens and Their Application in Guest-Host Polarizer
- PDF / 2,681,249 Bytes
- 9 Pages / 595 x 842 pts (A4) Page_size
- 54 Downloads / 231 Views
Article www.springer.com/13233 pISSN 1598-5032 eISSN 2092-7673
Syntheses and Properties of New Smectic Reactive Mesogens and Their Application in Guest-Host Polarizer Yang Ye1 Rui He1,2 Eunche Oh1 Shin-Woong Kang2 Seung Hee Lee2 Xiang-Dan Li3 Myong-Hoon Lee*,1
1
Graduate School of Flexible and Printable Electronics, Jeonbuk National University, Jeonju, 54896, Korea Department of BIN convergence Technology, Jeonbuk National University, Jeonju, 54896, Korea 3 Key Laboratory of Catalysis and Materials Science of the State Ethnic Affairs Commission & Ministry of Education, South-Central University for Nationalities, Wuhan, Hubei 430074, P. R. China 2
Received November 18, 2019 / Revised March 19, 2020 / Accepted May 8, 2020
Abstract: We designed and synthesized new smectic liquid crystalline monomers containing photopolymerizable acrylate groups and a mesogenic core unit composed of two benzene rings, one pyrimidine-based heteroaromatic ring and an acetylene linking group. The structures of monomers were characterized by 1H nuclear magnetic resonance spectroscopy, and their mesomorphic behaviors were investigated by differential scanning calorimetry and polarized optical microscopy. Both of monomers showed an enantiotropic phase transition behavior with exhibiting both nematic phase and highly ordered smectic phase. Both of monomers showed smectic phases during the cooling process in the temperature range of 144.2-94.0 oC and 154.0-85.8 oC, respectively. Neither of these compounds showed a homogeneous alignment even at various temperatures, and therefore, their 50:50 mixture was chosen for the preparation of guest-host mixture because of its lowest crystallization point, wide smectic phase temperature range and superior aligning property. Polymerizable “host-guest” mixture formulated from the host liquid crystalline monomer mixture, dichroic dye and additives was injected into the sandwiched glass substrates having rubbed alignment layers at the isotropic temperature. Subsequent in-situ photopolymerization by UV irradiation at room temperature successfully resulted in a thin film polarizer with good polarizing properties. The fabricated guest-host polarizer showed a dichroic ratio (DR) of 13.1 and a degree of polarization (DOP) of 95.5% with the thickness of 5 μm. Keywords: reactive mesogen, smectic phase, in-situ polymerization, host-guest system, coatable polarizer.
1. Introduction Polarizer is one of the basic and indispensable optical components in the current display devices such as liquid crystal displays (LCDs) and organic light emitting displays (OLEDs).1 The polarizer can be defined as an optical filter that lets light waves of a specific polarization pass through while blocking light waves of other polarizations.2 Not only being used as a light control valve in LCDs, linear polarizers have been widely used in various fields such as sensors, optofluidic components, and optoelectronics. Especially, they become an indispensable component in the flexible OLED display, because an anti-reflection film can be
Data Loading...
