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From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding

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Published on: March 24, 2018

Heliconical smectic phases formed by achiral molecules.

Jordan P Abberley¹, Ross Killah¹, Rebecca Walker¹

¹Department of Chemistry, King's College, University of Aberdeen, Aberdeen, AB24 3UE, UK.

Nature Communications

|January 17, 2018

Summary

Achiral molecules can form twisted helical structures in soft matter phases. This study reveals novel heliconical nematic and smectic phases with hierarchical helical structures, confirmed by X-ray analysis.

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Published on: June 9, 2010

Area of Science:

Soft matter physics
Materials science
Supramolecular chemistry

Background:

Chiral symmetry breaking is a key phenomenon in soft matter.
Achiral molecules can exhibit structural chirality in ordered phases, forming helical structures.
Understanding the formation and characteristics of these helical structures is crucial for developing novel materials.

Purpose of the Study:

To investigate the formation of twisted structures in soft matter phases using achiral asymmetric dimers.
To characterize the novel heliconical nematic (N_TB) and heliconical tilted smectic C (SmC_TB) phases.
To explore the relationship between molecular structure, helical formation, and molecular dynamics.

Main Methods:

Synthesis of achiral asymmetric dimers with an odd number of atoms in the spacer.
Phase behavior analysis of the synthesized dimers.
Structural characterization using resonant X-ray measurements.
Microscopy techniques to observe hierarchical structures.

Main Results:

Achiral asymmetric dimers successfully formed twisted structures in nematic and lamellar phases.
Novel tight pitch heliconical nematic (N_TB) and heliconical tilted smectic C (SmC_TB) phases were identified.
A gradual freezing of molecular rotation accompanied the formation of helical structures.
Hierarchical helical structures, including nanoscale helices and mesoscopic helical filaments, were observed in the HexI phase.
Short-pitch helical structures were confirmed by resonant X-ray measurements.

Conclusions:

Achiral molecules can self-assemble into complex helical structures in soft matter.
The design of molecular building blocks (achiral asymmetric dimers) is key to controlling helical formation.
The observed hierarchical structures and freezing of molecular rotation offer new avenues for designing advanced soft materials.