Novel dimeric cholesteryl derivatives and their smart thixotropic gels

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Organic Chemistry

Background:

• Developing novel gelators for organic solvents is crucial for applications in controlled release, sensing, and materials fabrication.
• Cholesteryl derivatives offer a promising scaffold for designing self-assembling soft materials due to their inherent amphiphilicity and structural rigidity.

Purpose of the Study:

• To design and synthesize novel LS(2)-type dimeric-cholesteryl derivatives.
• To investigate the gelation abilities of these compounds in various organic solvents.
• To explore the self-assembly mechanisms and properties of the resulting gels.

Main Methods:

• Synthesis of LS(2)-type dimeric-cholesteryl derivatives.
• Gelation studies in diverse organic solvents using room temperature mixing, heating-cooling cycles, and ultrasound treatment.
• Morphological analysis using Scanning Electron Microscopy (SEM).
• Structural and mechanistic investigations using Fourier-Transform Infrared (FT-IR) spectroscopy, Nuclear Magnetic Resonance (NMR) spectroscopy, and X-ray Diffraction (XRD).

Main Results:

• Three novel LS(2)-type dimeric-cholesteryl derivatives were successfully synthesized.
• The compounds demonstrated the ability to gel a wide range of organic solvents through multiple preparation methods.
• Compound 1 exhibited supergelator properties for Dimethyl Sulfoxide (DMSO) with a critical gelation concentration (cgc) of 0.04% w/v.
• The DMSO gel of compound 1 displayed excellent mechanical strength and thixotropic behavior.
• SEM revealed that gel morphology is influenced by gelator structure, concentration, solvent, and preparation method.
• FT-IR, NMR, and XRD studies indicated that hydrogen bonding and π-π stacking are key driving forces for gel formation, leading to a layered packing structure.

Conclusions:

• Novel dimeric-cholesteryl derivatives are effective low-molecular-weight gelators for organic solvents.
• Compound 1 is a highly efficient gelator for DMSO, forming a mechanically robust and thixotropic gel.
• The self-assembly process is driven by non-covalent interactions, including hydrogen bonding and π-π stacking, resulting in ordered structures.