Nanofibers and Vesicles Self-Assembled fromGemini Surfactant Complexes with Bile Salts

Nanofibers and vesicles are fabricated in aqueous solution by self-assembly of complexes of cationic Gemini surfactants ((C s H2s -α,ω-(Me2N+C m H2m+1Br-)2, m-s-m) and anionic bile salts (BS). Their morphology, structure, and properties are characterized by polarized optical microscopy (POM), transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM), and X-ray powder diffraction (XRD). The morphology of these aggregates was significantly influenced by minor structural changes of the building blocks, including the spacer and alkyl chain lengths of m-s-m, and the hydroxyl group number and position on the steroid skeleton of the BS. The formation of these aggregates is considered to arise mainly fromelectrostatic interactions, with contributions fromhydrogen bonding and hydrophobic interactions. The results obtained may be helpful for understanding the mechanisms of ionic self-assembly and aid the design of novel supramolecular aggregates.