Morphological Evaluation of Supramolecular Soft Materials Obtained through Co-Assembly Processes

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Organic Chemistry

Background:

• Low-molecular-weight gelators (LMWGs) self-assemble into supramolecular architectures via non-covalent interactions.
• The molecular-level understanding of synergistic molecular assembly remains incomplete.
• The 9-fluorenylmethoxycarbonyl (Fmoc) group is utilized to stabilize and direct molecular self-assembly.

Purpose of the Study:

• To investigate the self-assembly and co-assembly of Fmoc-protected peptides and amino acids into supramolecular gels.
• To explore gelation triggered by solvent/co-solvent changes and pH adjustments.
• To elucidate the relationship between molecular structure, assembly process, and resulting supramolecular morphology.

Main Methods:

• Utilized Fmoc-short peptide and four Fmoc-amino acids as building blocks.
• Triggered gelation using solvent/co-solvent methods and pH switching.
• Performed complex morphological analysis including Polarized Optical Microscopy (POM), Atomic Force Microscopy (AFM), Scanning Transmission Electron Microscopy (STEM), and X-ray Diffraction (XRD).

Main Results:

• Self-assembled gels exhibited diverse morphologies such as dendrimers, spherulites, and vesicles.
• Co-assembled supramolecular systems consistently displayed fibrillar morphologies due to specific molecular interactions.
• STEM confirmed the formation of a fibrous network in both self-assembled and co-assembled gels.
• XRD provided insights into the molecular arrangement within the gels.
• The Fmoc group was found to protect amino groups and enhance gelation via π-π interactions.

Conclusions:

• Fmoc-protected peptides and amino acids can effectively form supramolecular gels through self-assembly and co-assembly.
• The assembly pathway (self- vs. co-assembly) dictates the final supramolecular morphology.
• The Fmoc moiety plays a crucial role in facilitating gelation and influencing the assembly process through protective and interactive effects.