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Highly Ordered Columnar Structures from Hexa-peri-hexabenzocoronenes-Synthesis, X-ray Diffraction, and Solid-State
Fechtenkötter1, Saalwächter, Harbison
1Max-Planck-Institut für Polymerforschung, Postfach 3148, D-55021 Mainz (Germany).
Angewandte Chemie (International Ed. in English)
|December 14, 1999
Summary
Researchers improved molecular ordering in liquid crystals by adding phenyl rings to hexa(para-n-dodecylphenyl)hexabenzocoronene. This enhanced hexagonal order and molecular packing was confirmed using X-ray scattering and advanced NMR techniques.
Area of Science:
- Materials Science
- Organic Chemistry
- Supramolecular Chemistry
Background:
- Hexabenzocoronenes are known for their extended aromatic cores and ability to form liquid crystalline phases.
- Achieving long-range order in columnar mesophases is crucial for material properties and applications.
- Alkyl side chains are typically used to induce liquid crystallinity, but can sometimes hinder optimal packing.
Purpose of the Study:
- To enhance the long-range ordering in the columnar mesophase of a specific hexabenzocoronene derivative.
- To investigate the effect of inserting phenyl rings on the molecular packing and mobility within the liquid crystalline columns.
- To demonstrate a novel application of heteronuclear multiple-quantum magic-angle spinning (MAS) NMR for probing molecular dynamics in such systems.
Main Methods:
- Synthesis of a modified hexa(para-n-dodecylphenyl)hexabenzocoronene with phenyl ring insertions.
- X-ray scattering to characterize the long-range hexagonal order of the columnar mesophase.
- Heteronuclear multiple-quantum magic-angle spinning (MAS) Nuclear Magnetic Resonance (NMR) spectroscopy to probe molecular packing and mobility.
Main Results:
- Insertion of phenyl rings between the aromatic core and alkyl chains significantly improved long-range hexagonal ordering.
- X-ray scattering confirmed the enhanced hexagonal order of the columnar mesophase.
- Advanced NMR techniques revealed improved packing of the aromatic cores and provided insights into molecular mobility.
Conclusions:
- The strategic insertion of phenyl rings is an effective method for enhancing the columnar mesophase ordering in hexabenzocoronene derivatives.
- The study highlights the utility of advanced NMR techniques for detailed molecular-level characterization of liquid crystalline materials.
- This work contributes to the design of novel organic materials with improved structural organization for potential applications.
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