Mesoscopic Heterogeneity in Pore Size of Supramolecular Networks

Area of Science:

• Materials Science
• Supramolecular Chemistry
• Soft Matter Physics

Background:

• Supramolecular gels (SMGs) are formed from low molecular weight gelators, creating fibrous networks without covalent bonds.
• SMG networks have been traditionally considered homogeneous compared to chemically cross-linked polymer gels.
• Understanding SMG network structure is crucial for their application in various fields.

Purpose of the Study:

• To experimentally investigate and verify the existence of network heterogeneity in supramolecular gels.
• To characterize the spatial heterogeneity and its length scale within SMGs.
• To compare the heterogeneity of SMGs formed from gelators with varying peptide residue numbers.

Main Methods:

• Preparation of supramolecular gels (SMGs) using aqueous dispersions of gelators (PalGH, PalG2H, PalG3H).
• Tracking the thermal motion of probe particles within the SMG networks.
• Analysis of particle motion to infer spatial variations in network pore size and heterogeneity.

Main Results:

• Experimental evidence confirmed spatial heterogeneity in SMG networks.
• Particle motion varied depending on location, indicating differences in network pore size.
• The characteristic length scale of heterogeneity was found to be in the sub-micrometer to micrometer range.
• Heterogeneity length scale decreased in the order of PalG2H, PalG3H, and PalGH gels.

Conclusions:

• Supramolecular gel networks are not homogeneous but exhibit spatial heterogeneity.
• The degree and length scale of heterogeneity can be tuned by the gelator structure (peptide residue number).
• These findings challenge previous assumptions and provide insights into SMG network architecture.