Thixotropic and Injectable Nature of Supramolecular Aqueous Gels Derived from N,N'-Dibenzoyl-L-cystine and the Effects of Esterification

The thixotropic and injectable properties of physical aqueous gels derived from N,N'-dibenzoyl-L-cystine (1, DBC) and its dimethyl ester (2) at room temperature (RT) are described. The characterization of the materials was carried out by oscillatory rheological measurements, including thixotropy-loop tests, and field emission scanning electron microscopy (FE-SEM). Moreover, the effects of gelator concentration and added DMSO on the gel stability are also discussed. Interestingly, comparative studies revealed, among other effects, that esterification of DBC has a positive effect on both the critical gelation concentration (CGC(1) = 4.5 mM; CGC(2) = 2.0 mM) and the gel-to-sol transition temperature of the gels (Tgel(1) = 65 °C; Tgel(2) = 78 °C), whereas the thixotropic-response was significantly hampered.