Abstract
A new series of Schiff base liquid crystal have been prepared and studied. Schiff bases of p-alkyl aniline derivatives and 4-phenyl pyridine-4′-carbaldehyde were prepared. The terminal alkyl groups substituting aniline are of varied chain length, namely C8, C12 and C14. The structures of the compounds were elucidated by 1H NMR and 13C NMR. The mesomorphic thermal and optical characteristics of the samples were determined via differential thermal analysis (DSC) and polarization optical microscopy (POM). All compounds exhibit enantiotropic dimorphic mesophase behaviour, referred to as smectic X1 (SmX1) and smectic X2 (Sm A). Experimental results obtained for the mesophases were correlated with density functional theory (DFT) theoretical calculations. The results of the new series are further compared to two series of compounds bearing pyridine (two ring Schiff bases) and biphenyl, respectively, in their mesogens. The series of compounds of one pyridine ring are generally not mesomorphic. The results indicate that the alkyl chain length has a strong impact on the mesomorphic characteristics and thermal stabilities of the different mesophases. As a trend, the temperature ranges of both of smectic mesophases of all compounds are higher in new compounds bearing the 4-phenyl pyridine moiety. In addition, the total mesophase range is generally higher in the new compounds when compared to their biphenyl analogues. Finally, theoretical DFT calculations were performed to illustrate the experimental finding of the mesomorphic behaviour in terms of the molecular geometry and aromaticity, π–π stacking and LOL-π.
Highlights
Liquid crystals (LCs) are an attractive class of soft matter with properties that fall somewhere between liquids and solid crystals [1,2,3]. They have gained a huge amount of attention due to their very promising applications in various technological fields such as organic field effect transistors (OFETs) [4], Pancharatnam-Berry (PB) microlense [5], liquid crystal elastomers [6], sunlight-driven polymer actuators [7], photovoltaics [8], biosensors [9,10,11] and telecommunications [12]
LC material with unique properties is the chemical modification of geometry which has proven to be one of the finest strategies
In calamitic liquid crystals, the mesomorphic behaviour can be significantly altered by even a minor change in the molecular geometry including various connecting units, variation in terminal chains, the inclusion of heteroatoms/heterocyclic ring and the existence of various laterally substituted atoms/groups [13]
Summary
Liquid crystals (LCs) are an attractive class of soft matter with properties that fall somewhere between liquids and solid crystals [1,2,3] They have gained a huge amount of attention due to their very promising applications in various technological fields such as organic field effect transistors (OFETs) [4], Pancharatnam-Berry (PB) microlense [5], liquid crystal elastomers [6], sunlight-driven polymer actuators [7], photovoltaics [8], biosensors [9,10,11] and telecommunications [12]. Several types and classes of substituents with different polarity have been repeatedly amalgamated into diverse LC structures to alter the conformational and geometrical preferences, the mesomorphic properties, the transition temperature and some additional crucial physical properties not just important for designing and developing new low cost LC materials with enhanced properties appropriate for display technologies, and for recognizing the structure–property relationship
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
