Smectic liquid crystals from supramolecular guanidinium alkanesulfonates

Area of Science:

• Materials Science
• Solid-State Chemistry
• Crystallography

Background:

• Guanidinium alkanesulfonates are a class of compounds known for their potential liquid crystalline properties.
• Understanding their thermotropic polymorphism is crucial for developing novel materials with tunable phase behavior.

Purpose of the Study:

• To investigate the thermotropic polymorphism of guanidinium alkanesulfonates with varying alkyl chain lengths (n=6-18).
• To elucidate the relationship between molecular structure, hydrogen bonding, and observed mesophases.
• To determine if the supramolecular arrangement in the crystal phase is retained in higher-temperature smectic phases.

Main Methods:

• Optical microscopy and differential scanning calorimetry (DSC) for thermal analysis.
• Infrared (IR) spectroscopy to study hydrogen bonding interactions.
• Dilatometry for precise molecular volume measurements.
• X-ray diffraction to analyze crystal and smectic phase structures.

Main Results:

• The study identified thermotropic polymorphism in guanidinium alkanesulfonates (n=6-18).
• X-ray diffraction confirmed the presence of crystal, smectic A, and ordered smectic phases.
• Analysis revealed that the supramolecular arrangement observed in the crystal phase is preserved in the smectic phases at elevated temperatures.

Conclusions:

• Guanidinium alkanesulfonates display thermotropic polymorphism, transitioning through distinct crystalline and smectic phases.
• The molecular packing and hydrogen bonding established in the crystal lattice are maintained in the higher-temperature smectic phases.
• This structural persistence suggests a robust supramolecular organization influencing the material's phase behavior.