Fmoc-diphenylalanine (FmocFF or FmocPhePhe) is an important low molecular weight hydrogelator. Gelation can be induced by either lowering the pH of an aqueous solution of FmocFF or by the addition of water to a solution of FmocFF in a solvent such as DMSO. Despite the volume of literature on FmocFF, the mechanical properties reported for the gels vary significantly over four orders of magnitude and the origins of this variability is unclear. Here, we study systematically the mechanical properties of FmocFF gels prepared with different protocols. We demonstrate that the final pH of the gels is the principal determinant of the mechanical properties independently of the method of gel formation. We also show that additional variability arises from experimental factors such as the fraction of DMSO or the nature of the buffers used in selected systems.Scheme 1 Structure of FmocFF.Scheme 2 Hydrolysis of GdL to gluconic acid.

Addition of divalent cations to a solution of a naphthalene-diphenylalanine that forms worm-like micelles at high pH results in the formation of a rigid, self-supporting hydrogel.

We describe the effect of polymeric additives on the molecular gelation of two N-functionalized dipeptides. Hydrogelation was triggered by the addition of aqueous solutions to the dipeptide in DMSO. Gels can be formed in the presence of high concentrations of additives. The rheological properties of the gels are also remarkably tolerant to the presence of polymeric additives. When dextrans were used as additives, the effect on the rheological properties was determined by the viscosity of the dextran solutions. Examining a range of other polymer additives, it is clear that polymer structure is also an important parameter.

Correction for ‘Fmoc-diphenylalanine hydrogels: understanding the variability in reported mechanical properties’ by Jaclyn Raeburn et al., Soft Matter, 2012, 8, 1168–1174, https://doi.org/10.1039/C1SM06929B.