title: 5-Methyl Salicylic Acid-Induced Thermo Responsive Reversible Transition in Surface Active Ionic Liquid Assemblies: A Spectroscopic Approach.
abstract: This article describes the formation of stable unilamellar vesicles involving surface active ionic liquid (SAIL), 1-hexadecyl-3-methylimidazolium chloride (C16mimCl), and 5-methyl salicylic acid (5mS). Turbidity, dynamic light scattering (DLS), transmission electron microscopy (TEM), and viscosity measurements suggest that C16mimCl containing micellar aggregates are transformed to elongated micelle and finally into vesicular aggregates with the addition of 5mS. Besides, we have also investigated the photophysical aspects of a hydrophobic (coumarin 153, C153) and a hydrophilic molecule (rhodamine 6G (R6G) perchlorate) during 5mS-induced micelle to vesicle transition. The rotational motion of C153 becomes slower, whereas faster motion is observed for R6G during micelle to vesicle transition. Moreover, the fluorescence correlation spectroscopy (FCS) measurements suggest that the translational diffusion of hydrophobic probe becomes slower in C16mimCl-5mS aggregates in comparison to C16mimCl micelle. However, a reverse trend in translational diffusion motion of hydrophilic molecule has been observed in C16mimCl-5mS aggregates. Moreover, we have also found that the C16mimCl-5mS containing vesicles are transformed into micelles upon enhanced temperature, and it is further confirmed by turbidity, DLS measurements that this transition is a reversible one. Finally, temperature-induced rotational motion of C153 and R6G has been monitored in C16mimCl-5mS aggregates to get a complete scenario regarding the temperature-induced vesicle to micelle transition.
authors.affiliation: Department of Chemistry, Indian Institute of Technology , Kharagpur 721302, WB, India.
authors.forename: Arpita
authors.initials: A
authors.lastname: Roy
authors.affiliation: Department of Chemistry, Indian Institute of Technology , Kharagpur 721302, WB, India.
authors.forename: Rupam
authors.initials: R
authors.lastname: Dutta
authors.affiliation: Department of Chemistry, Indian Institute of Technology , Kharagpur 721302, WB, India.
authors.forename: Pavel
authors.initials: P
authors.lastname: Banerjee
authors.affiliation: Department of Chemistry, Indian Institute of Technology , Kharagpur 721302, WB, India.
authors.forename: Sangita
authors.initials: S
authors.lastname: Kundu
authors.affiliation: Department of Chemistry, Indian Institute of Technology , Kharagpur 721302, WB, India.
authors.forename: Nilmoni
authors.initials: N
authors.lastname: Sarkar