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ABSTRACT
A series of non-linear S-shaped liquid crystal oligomers wherein the molecule consists of biphenylene moiety as a central core unit and two symmetrical side arms azobenzene moieties joined to catechol as a linkage group have been successfully synthesised and characterised. The members in this series possess different inner spacer with carbon number n ranging from 4 to 9 while the outer spacer length located in azobenzene moieties are remains unaltered. The members with even parity exhibit monotropic phase, whereas homologues with odd parity display enantiotropic phase. The appearance of nematic, smectic A and smectic B phases was validated with texture observation under polarised light and X-ray diffraction (XRD). The XRD study on the S-shaped oligomer indicates that the arrangement of smectic phase exists as an intercalated structure. The S-shaped oligomer shows photoisomerisation properties in solution whereby the trans to cis isomerisation for this molecule is accomplished 1140 s, whereas reverse process under thermal back reaction occurred in 4620 min.
Graphical Abstract
Acknowledgement
The main author (G.-Y.Yeap) would like to acknowledge Universiti Sains Malaysia for funding this project [RU Grant No. 1001/PKIMIA/811223] and Malaysian Ministry of Education [FRGS Grant No. 203/PKIMIA/6711422].F. Osman wishes to thank the MOHE for the scholar assistantship under the MyBrain15 scheme.
Disclosure statement
No potential conflict of interest was reported by the authors.
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