Synthesis and smectogenic properties of novel phloroglucinol-based star-shaped liquid crystals containing three peripheral alkyloxylated Schiff base arms

Abstract

A series of symmetrical trimeric liquid crystalline compounds of which the molecular structure with a central core of 1,3,5-benzene attached by three rod-like mesogenic Schiff base moieties via the propylene spacers and ether linkages has successfully been synthesised and characterised by infra red and nuclear magnetic resonance spectroscopic techniques. All the star-shaped compounds in this series exhibit predominantly SmC phase except the analogue possessing terminal C₈H₁₇ group. It is apparent that the members with even parity from C₁₀H₂₁ to C₁₆H₃₃ show enantiotropic SmC phase while the member with longest terminal chain of C₁₈H₃₇ is inclined to monotropic smectogen. The X-ray diffraction measurements reveal that the tilted smectic layer structures of the SmC phase are confirmed to have an obvious sharp peak at small angles of 2θ ∼ 1.03°–1.48° with d-spacing values of 4.01–4.58 nm, which are corresponding to tilt angles of ∼48° in the SmC phase.

Keywords:

• phloroglucinol
• Schiff bases
• star-shaped liquid crystals
• smectic C
• XRD

Acknowledgements

The author (G.Y.Yeap) would like to thank Malaysian Ministry of Higher Eduation (MOHE) for funding this project through the Fundamental Research Grant Scheme (No. 203/PKIMIA/6711265). Y.H.Ooi would also like to acknowledge MOHE for the MyBrain15 fellowship.