Pathway complexity in fibre assembly: from liquid crystals to hyper-helical gelmorphs

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Chemical Engineering

Background:

• Pathway complexity in self-assembly can lead to diverse material outcomes from identical molecular components.
• Chiral molecules offer unique opportunities for creating complex supramolecular structures.
• Understanding assembly pathways is crucial for controlling material morphology and properties.

Purpose of the Study:

• To investigate how varying assembly conditions influence the self-assembly of a chiral acyl-semicarbazide gelator.
• To characterize the different supramolecular structures (gels and liquid crystals) formed by the gelator.
• To correlate the observed morphologies with the underlying molecular conformations and assembly kinetics.

Main Methods:

• Synthesis of a chiral acyl-semicarbazide gelator.
• Controlled self-assembly experiments under varied conditions (solvent, temperature, concentration).
• Morphological characterization using techniques like electron microscopy.
• Rheological property measurements of the formed gels.
• Spectroscopic analysis to study molecular conformations and kinetics.

Main Results:

• The chiral gelator formed three distinct gel morphologies (hyperhelical, tape-fibre, liquid crystalline-derived thin fibril) and lyotropic liquid crystalline droplets.
• Each gelmorph exhibited significantly different rheological properties.
• The gelator exists in solution as three slowly interconverting conformers, with all gels comprising a single unsymmetrical, intramolecular hydrogen-bonded conformer.
• Formation of the hyperhelical gel was found to be cooperative, potentially involving interactions with a non-gelling conformer.

Conclusions:

• Assembly pathway complexity is a critical determinant of material properties, even from a single molecular component.
• The dynamic conformational library of the gelator, coupled with pathway-dependent interactions, drives the formation of diverse supramolecular materials.
• This study highlights a mechanism for generating materials with contrasting properties through controlled self-assembly pathways.