Monolayer Filaments versus Multilayer Stacking of Bent-Core Molecules

Area of Science:

• Materials Science
• Supramolecular Chemistry
• Liquid Crystals

Background:

• Bent-core liquid crystals exhibit unique B4 lamellar phases.
• These materials can self-assemble into complex supramolecular structures in solution and bulk.
• Understanding structure-property relationships is crucial for designing advanced materials.

Purpose of the Study:

• To investigate the self-assembly behavior of bent-core materials in gels and bulk states.
• To correlate molecular structure with the formation of helical ribbons and layered stacks.
• To elucidate the origin of optical activity in these materials and its dependence on structural organization.

Main Methods:

• Dissolution of bent-core materials in organic solvents to form gels.
• Characterization of bulk samples and gel structures using microscopy and spectroscopy.
• Development of a theoretical model to explain optical activity based on layered structures.

Main Results:

• Gels formed helical ribbons from molecular monolayers and bilayers.
• Bulk samples showed strongly deformed stacks of 5-6 layers.
• Helical filament width and pitch increased with molecular length.
• Bulk samples were optically active, while gels were not.
• Optical activity originated from crystal layer structure, not filament helicity.
• Fluorescence increased and redshifted in gels compared to the sol state.

Conclusions:

• The self-assembly of bent-core materials is highly dependent on the sample state (gel vs. bulk).
• Molecular length is a key factor in determining the dimensions of self-assembled structures.
• Optical activity is intrinsically linked to the layered crystalline structure, with implications for material design.
• Theoretical modeling supports the observed optical activity trends related to layer stacking.