Vesicle formation with amphiphilic chitosan derivatives and a conventional cationic surfactant in mixed systems

The self-assembly behavior of mixed systems consisting of amphiphilic chitosan derivatives C(n)-OCMCS (n = 4, 6, 8) and the conventional cationic surfactant cetyltrimethylammonium bromide (CTAB) is investigated. Transmission electron microscopy (TEM), dynamic light scattering (DLS), small-angle X-ray diffraction (XRD), UV-vis spectra, and zeta potential measurements have been utilized to characterize the microstructures of C(n)-OCMCS/CTAB mixtures in aqueous solutions. Spherical vesicles are formed spontaneously in the C(n)-OCMCS (n = 4, 6, 8)/CTAB mixed systems, and the increased hydrophobic chain length of C(n)-OCMCS enhances the ability to form vesicles. The addition of NaBr with higher concentrations to the vesicle system transforms vesicles into micelles, and an increase in temperature decreases the vesicle size. The results indicate that the main driving forces controlling vesicle formation may be attributed to the strong electrostatic interactions as well as the hydrophobic interactions, and also the hydrogen bonding between C(n)-OCMCS molecules. (C) 2011 Elsevier Inc. All rights reserved.