The synthesis, mesomorphic and dielectric investigation of new unsymmetrical bent-core mesogens derived from 3-hydroxybe
- PDF / 2,397,846 Bytes
- 13 Pages / 595.276 x 790.866 pts Page_size
- 71 Downloads / 154 Views
ORIGINAL PAPER
The synthesis, mesomorphic and dielectric investigation of new unsymmetrical bent‑core mesogens derived from 3‑hydroxybenzoic acid Hale Ocak1 · Esma Ahlatcıoğlu Özerol2 · Fulya Çağla Çelikel1 · Mustafa Okutan3 · Belkız Bilgin Eran1 Received: 22 February 2020 / Accepted: 16 May 2020 © Institute of Chemistry, Slovak Academy of Sciences 2020
Abstract The synthesis, mesomorphic and dielectric investigation of new unsymmetrical bent-core mesogens derived from 3-hydroxybenzoic acid central core with linked two rodlike units carrying (S)-3,7-dimethyloctyloxy group and an n-alkyloxy chain at both terminals are presented. The liquid crystalline properties of the new unsymmetrical bent-core materials have been investigated by polarizing optical microscopy and differential scanning calorimetry. New compounds with the reversed ester linking unit exhibit a monotropic or enantiotropic columnar mesophase at lower temperatures as compared to analogs with a straight chain depending on the presence of the branched (S)-3,7-dimethyloctyloxy terminal chain. Dielectric measurements for one of the bent-core mesogens, 3-[[4-[[4-(octyloxy)benzoyl]oxy]benzoyl]oxy]benzoic acid 4-[[4-((S)3,7-dimethyloctyloxy)phenoxy]carbonyl]phenyl ester (OBDPE), have been carried out on the angular frequency range from 25.12 to 50265k rad/s at different temperatures. Thanks to dielectric measurements, real and imaginary dielectric constant, conductivity mechanism and dielectric relaxation mechanism of OBDPE were obtained. Graphic abstract
Keywords Liquid crystals · Bent-core compounds · 3-Hydroxybenzoic acid derivatives · Columnar mesophase · Dielectric measurement
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11696-020-01203-4) contains supplementary material, which is available to authorized users. * Hale Ocak [email protected] Extended author information available on the last page of the article
Introduction Bent-core liquid crystals have attracted great interest since the discovery of their polar switching behavior (Niori et al. 1996) in their mesophases. The polar ordering of bentshaped materials generates structural layer chirality, which
13
Vol.:(0123456789)
results in ferroelectric or antiferroelectric properties (Kishikawa et al. 1999). A great number of symmetrical and unsymmetrical bentcore liquid crystals have been reported till date. The mesophases exhibited by these molecules have been assigned as B-phases, but also a large number of bent-shaped materials which show nematic (Schröder et al. 2003; Bailey et al. 2009; Kohout et al. 2009) and columnar phases (Reddy and Tschierske 2006; Gorecka et al. 2008) have been reported. In recent years, bent-core compounds exhibiting various tilted and non-tilted smectic phases have attracted significant interest (Dunemann et al. 2005; Pratibha et al. 2000; Keith et al. 2010; Gupta et al. 2011, Pociecha et al. 2006; Shreeninvasa Murthy and Sadashiva 2004a). The molecular structure of bent-core liquid crystals is composed of
Data Loading...
