Supramolecular Hydrogels Based on L-Phenylalanine Derivatives with a Positively Charged Terminal Group

A new hydrogelator based on L-phenylalanine with a long hydrophobic chain and positively charged terminus was synthesized, and its gelation behavior in H2O was investigated. Polarized optical microscopy (POM), field emission scanning electron microscopy (FE-SEM). and X-ray diffraction (XRD) results indicate that the hydrogelator self-assembles into fibres-like aggregates which then lead to the formation of a hydrogel. H-1-NMR and CD spectra of hydrogels and aqueous solution revealed that intermolecular H-bonding between the amide groups was the driving force for gelation. A luminescence in which ANS (8-anilinonaphthalene-1-sulfonic acid) was used as a probe, indicated that the hydrophobic interactions between long chains were the driving force for gelation. Consequently, it was proved that the hydrogelator self-assembles into fibre-like agggregates and then forms supramolecular hydrogels through the H-bonding and hydrophobic interactions.