Synthesis and mesomorphic properties of new organosiloxane chiral calamitic liquid crystals


OCAK H. , Karaağaç B., AKDAŞ KILIÇ H. , Jeannin O., Camerel F., BİLGİN ERAN B.

Journal of Molecular Liquids, vol.348, 2022 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 348
  • Publication Date: 2022
  • Doi Number: 10.1016/j.molliq.2021.118077
  • Journal Name: Journal of Molecular Liquids
  • Journal Indexes: Science Citation Index Expanded, Scopus, Academic Search Premier, Chemical Abstracts Core, Chimica, Compendex, INSPEC
  • Keywords: Liquid crystals, Chirality, Calamitic, Organosiloxane, (S)-2-methylbutoxy group, PHASE-TRANSITION, POLAR ORDER, CORE, DIMERS, SERIES

Abstract

© 2021 Elsevier B.V.A new chiral calamitic compound consisting of a phenyl core that is connected through ester linkers to a benzoate carrying a chiral (S)-2-methylbutoxy group at one side and a biphenyl carboxylate with an undecenyloxy chain at other side has been synthesized. Additionally, the siloxane substituted derivatives and a dimer with these two identical chiral calamitics linked by a disiloxane spacer have been obtained via hydrosilylation reaction to study the effect of combining the chiral moiety and siloxane segments within the same structure on liquid crystalline properties. The chiral calamitic compound and derivatives with a siloxane end-group or a siloxane spacer have been characterized using classical spectroscopic methods (1H NMR, 13C NMR, 29Si NMR and MS) and elemental analysis (EA). The liquid crystalline properties of all new compounds were investigated by differential scanning calorimetry, optical polarizing microscopy, X-ray scattering and electro-optic methods. With the introduction of a siloxane end-group to the vinyl-terminated calamitic compound exhibiting enantiotropic chiral nematic phase (N*) and chiral tilted smectic phase (SmC*), the occurrence of stable smectic phase was strongly promoted. In a similar way, the dimer with two identical calamitic mesogens connected by a disiloxane spacer exhibited a wider smectic mesophase interval in addition to the presence of N* mesophase. The new mesogens exhibit a ferroelectric switching with PS of around 200 nC cm−2 in their chiral tilted smectic (SmC*) mesophase range. The transition temperatures of organosiloxanes are considerably lower than that of olefinic precursor.