Hydrophobically Driven Morphologically Diverse Self-Assembled Architectures of Deoxycholate and Imidazolium-Based Biamphiphilic Ionic Liquids in Aqueous Medium

Biamphiphilic ionic liquids (BAILs) having amphiphilic cation and anion are thought to exhibit improved surface activity and colloidal stability to be utilized in different applications. For their effective use, a control over synergetic hydrophobic and electrostatic interactions between oppositely charged ions along with the possibility of tuning of hydrophobicity of the core of aggregates is required. Focusing on this, new BAILs comprising a bile salt anion, deoxycholate, [DC](-), and 1-alkyl-3-methylimidazolium cations, [C(n)mim](+) (n = 2, 4, 6, 8, and 12), were synthesized and characterized for their behavior at air-solution interface as well as in bulk. The synthesized BAILs exhibit high surface activity and self-assemble in the form of different architectures ranging from nanosheets (NSs), nanorods, and vesicles with varying hydrophobicities of the formed core of aggregates, depending on the length of alkyl chain of [C(n)mim](+). Analysis of various parameters obtained from investigated techniques suggested the changing role of [C(n)mim](+) from a counterion (n = 2 and 4) to a cosurfactant (n = 8 and 12) via a borderline case of [C(6)mim](+). This changeover in the nature of counterion controlled by hydrophobicity of alkyl chain resulted in morphological diversification in self-assembled architectures via varying set of interactions. It is believed that the present work would offer new perspectives in the self-assembly phenomenon of surfactants in general and surface active ionic liquids in particular to devise new strategies for inducing morphology-dependent functionality in self-assembled structures of BAILs.