Co-assembly behaviors and rheological properties of a salt-free catanionic tetrapeptide/surfactant system in water

The co-assembly behavior of a short tetrapeptide (I3E) and a zwitterionic surfactant (dodecyldimethylamine oxide, C14DMAO) in water have been systematically investigated. The microstructures and properties of the I3E/C14DMAO mixture were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM) and a HAAKE rotational rheometer. Fourier transform infrared (FT-IR), X-ray diffraction (XRD) and circular dichroism (CD) were used to explore the formation of different microstructures. It was found that, with the increasing of C14DMAO, the co-assembly of the I3E/C14DMAO mixture changed from nanofibers to nanosheets, and then finally to wormlike micelles and spherical micelles. And the rheological properties of the mixtures also changed with the increasing of C14DMAO concentration accordingly.