Synthesis, phase transition behaviour and dielectric properties of smectogenic palm-based liquid crystals containing schiff base ester and phenyl ring

•Palm fatty acid of different chain length (C12, C16 and C18) as flexible moiety in the synthesis of thermotropic liquid crystals.•All synthesized palm-based liquid crystals are monomorphic in nature exhibiting only smectic A phase with lower stability as flexible chain length increases.•Weaker diel...

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Bibliographic Details
Published in:Journal of molecular structure 2023-06, Vol.1282, p.135168, Article 135168
Main Authors: Lee, Weng Nam, Salleh, Noordini M., Velayutham, T.S., Cheng, Sit-Foon
Format: Article
Language:English
Subjects:
Dielectric constant
Flexible alkyl chain
Green chemistry
Palm fatty acids
Schiff base
Smectic
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Summary:•Palm fatty acid of different chain length (C12, C16 and C18) as flexible moiety in the synthesis of thermotropic liquid crystals.•All synthesized palm-based liquid crystals are monomorphic in nature exhibiting only smectic A phase with lower stability as flexible chain length increases.•Weaker dielectric strength observed with longer flexible chain length.•The presence of an additional phenyl ring and a polar terminal Br group significantly enhanced mesophase stability. Smectogenic liquid crystals (LCs) play an important role in various technological applications due to their interesting morphologies and defects. With incessant effort to add value to palm oil, another two series of palm-based liquid crystals (PBLCs), namely PB1a-PB3a and PB1b-PB3b, utilizing palm fatty acids as flexible alkyl chain have been synthesized. The appearance of smectic A phase for all PBLCs was authenticated by Polarizing Optical Microscopy (POM) and further verified by Differential Scanning Calorimetry (DSC) and Small Angle X-ray Scattering (SAXS). Results revealed that the mesophase range of all synthesized LCs is highly dependent on flexible alkyl chain length, the presence of polar terminal substituent as well as the breath to width ratio of mesogenic core. Dielectric measurements show that the dielectric strength is also affected by the length of the flexible alkyl chain. It is worth noting that, as far as mesophase range is concerned, PBLCs were found to be far superior over other structurally related compounds that can be found in the literature. [Display omitted]
ISSN:0022-2860
1872-8014
DOI:10.1016/j.molstruc.2023.135168