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

Abstract

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 selfassemble 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.

Transition Mechanism from Nonlamellar to Well-Ordered Lamellar Phases: Is the Lamellar Liquid-Crystal Phase a Must?

“…One important question in this regard concerns the transition mechanism between lamellar and nonlamellar structures and phases of amphiphilic molecules. On one hand, we see reports very often on the transitions between a nonlamellar phase and a lamellar liquid-crystal (L α ) phase. − Efforts have been made to study the transition mechanism from L α to hexagonal (H) phases, and cubic phases have been identified during the transitions in some cases. − On the other hand, there have also been reports on the direct transitions between a nonlamellar phase and an ordered lamellar phase. − Taking ionic liquid surfactant 1-hexadecyl-3-methyl­imidazolium chloride ([C 16 mim]­Cl) as an example, Kaper and Smarsly found that its aqueous dispersions transformed from the H or micellar (M) phase to the lamellar-crystal (L c ) phase directly by increasing the [C 16 mim]­Cl concentration (0–100 wt %) at room temperature . In a previous study, our group investigated the crystallization behavior of [C 16 mim]Cl aqueous dispersions and found that the nonlamellar M/H phase transformed to the ordered L c or lamellar-gel (L β ) phase directly upon cooling .…”

Cholesterol Mediated Stable Vesicles: A Nano Drug Delivery Vehicle for Anti‐cancer Drugs Curcumin and 5‐Fluorourecil

“…FRET has lately been employed by a group of studies to examine self‐assembled structures in surfactant and polymeric‐based systems [11,56,61,62] . The usual form of Förster theory could be used to measure the distance between the donor and acceptor (D‐A) in a surfactant‐based aggregated system.…”

Self-Assembly of Amphiphilic Compounds as a Versatile Tool for Construction of Nanoscale Drug Carriers

“…Sodium cholate is known for its capability to act as a transdermal enhancer [ 84 ] and additive to mono- and dicationic surfactant solutions significantly modifying their morphological behavior [ 85 ] and release profile of cargo encapsulated in self-assembled drug nanovehicles [ 86 ]. Sodium deoxycholate was reported as part of biamphiphiles, ionic compounds with both cationic and anionic amphiphilic nature, which aggregate shape could be accurately controlled [ 87 ]; micellar catalyst for the synthesis of 1,2,3-triazole derivatives; their characteristics is superior in comparison with those of conventional surfactants CTAB and Triton-X-100 [ 88 ]. Sodium taurodeoxyholate was documented as a compound for regulation of solubility of steroid drug in surfactant micellar solutions and biorelevant media [ 89 ] and as a component of composition for albendazole delivery for the treatment of lung parasites [ 90 ].…”