Study on Synthesis and Hydrogelation of Hydrogelators Based on Cyclo(L-Lys-L-Lys)

Fmoc mono-substituted cyclo(L-Lys-L-Lys) (FL-NH₂) was fist synthesized under strict control of the feed ratio. Thereafter, FL-NH₂ was further reacted with cyclic anhydrides, in which three thermo-reversible low molecular weight hydrogelators were obtained. A study on the impact of the aliphatic chain length of cyclic anhydrides on the gelation performance was carried out. In particular, the glutaric anhydride acrylated derivative (FL-Ga) shows a better hydrogel ability. The TEM and SEM observations reveal that the resulting hydrogelators are self-assembled into fibrous aggregates, which are further closely intertwined to form a 3D supramolecular network structure. The hydrogen bond and π-π stacking interactions play a cooperative role during the self-assembly of hydrogelators. Based on XRD patterns of the xerogel prepared from the hydrogel of FL-Ga and Rietveld method, a possible molecular packing model of single layer membrane was also deduced.