Phase behaviour of star-shaped binary mixtures of triphenylbenzenes, triphenylboroxines and triphenyltriazines

ABSTRACT

Star-shaped nonaalkoxy-1,3,5-triphenyltriazines were prepared and their mesomorphism was investigated by differential scanning calorimetry (DSC), polarised optical microscopy (POM) and X-ray diffraction (WAXS and SAXS). Compounds with chain lengths C₉ – C₁₂ displayed enantiotropic hexagonal columnar mesophases over a wide range of temperature. Their similarity in molecular size and mesomorphism prompted us to study their binary mixtures with previously reported planar 1,3,5-triphenylboroxines and propeller-shaped 1,3,5-triphenylbenzenes. All three compounds are fully miscible in their hexagonal columnar mesophases, but mixtures of planar with propeller-shaped compounds generated columnar stacks that contain only one type of molecule to avoid their shape incompatibility. However, the two types of columnar stacks were fully miscible which circumvented macroscopic phase separation.

GRAPHICAL ABSTRACT

KEYWORDS:

• Columnar
• discotic
• star-shaped
• binary mixtures

Acknowledgments

Generous financial support by the Deutsche Forschungsgemeinschaft (grant # LA907/17-1), the Ministerium für Wissenschaft, Forschung und Kunst des Landes Baden-Württemberg (Ontario-Baden-Württemberg fellowship for H. T.), the Bundesministerium für Bildung und Forschung (shared instrumentation grant # 01 RI 05177) and the Deutsche Akademische Austauschdienst (DAAD travel grant for T. W.) is gratefully acknowledged. S. H. E. and H. T. thank NSERC for financial support (RGPIN/05706-2014 and C.G.S.M. and P.G.S.D. scholarships).

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

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Additional information

Funding

This work was supported by the Deutsche Forschungsgemeinschaft [LA907/17-1];Canadian Network for Research and Innovation in Machining Technology, Natural Sciences and Engineering Research Council of Canada [RGPIN/05706-2014];Deutscher Akademischer Austauschdienst;Ministerium für Wissenschaft, Forschung und Kunst Baden-Württemberg;Bundesministerium für Bildung und Forschung [01 RI 05177].