Nonamphiphilic assembly in water: polymorphic nature, thread structure, and thermodynamic incompatibility

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Physical Chemistry

Background:

• Self-assembly of water-soluble molecules is entropically difficult.
• Understanding nonamphiphilic assemblies in water is crucial for developing new materials.

Purpose of the Study:

• To design and synthesize water-soluble aromatic molecules capable of forming nonamphiphilic assemblies and chromonic liquid crystals.
• To investigate the assembly behavior and liquid crystal phase formation in aqueous solutions.

Main Methods:

• Synthesis of novel water-soluble dichromonyl molecules.
• Characterization of liquid crystal phases using birefringence.
• Small-angle neutron scattering (SANS) to determine assembly structures.
• Investigating the effect of adding monoanionic and dianionic molecules.

Main Results:

• A new molecule, 5'DSCG-diviol, was synthesized and exhibits a large birefringent phase.
• Nonamphiphilic assemblies and chromonic liquid crystal phases were formed in water.
• SANS revealed concentration-independent rod-shaped assemblies.
• Monoanionic molecules disrupted the liquid crystal phase, while dianionic molecules retained it.

Conclusions:

• A novel assembly structure for nonamphiphilic molecules in water, termed molecular threads, was proposed.
• These threads consist of small molecules linked by salt bridges and stacked aromatic groups, heavily hydrated.
• Mixing different molecules can lead to new liquid crystals or phase segregation due to thermodynamic incompatibility.