Solution Behavior of Triblock Copolymer in the Presence of Ionic Liquids: A Comparative Study of Two Ionic Liquids Possessing Different Cations with Same Anion

A comparative study of two ionic liquids (ILs) with same anion and different cations on the phase transition changes of aqueous solution of a commonly used triblock copolymer poly­(ethylene glycol)-<i>block</i>-poly­(propylene glycol)-<i>block</i>-poly­(ethylene glycol) (PEG–PPG–PEG) (or Pluronic F-108), is undertaken using fluorescence spectroscopy, dynamic light scattering (DLS), viscosity (η), Fourier transform infrared (FT-IR) spectroscopy and nuclear magnetic resonance (NMR) techniques. Furthermore, to demonstrate it by direct visualization of various self-assembled morphologies, we employed field emission scanning electron microscope (FESEM). The two ILs include 1-allyl-3-methylimidazolium chloride ([Amim]­[Cl]) and 1-benzyl-3-methylimidazolium chloride ([Bzmim]­[Cl]). The results demonstrate that the addition of ILs alter the critical micellization temperature (CMT) toward lower temperatures. The extent to which the CMT altered is observed to be significantly more for [Bzmim]­[Cl] as compared to [Amim]­[Cl]. The charge and size of cations, presence of ion-pair interactions between the ions of ILs and the hydrophobic part PG are the reasons for these observations. It is noted that the changes in the properties of aqueous PEG–PPG–PEG upon addition of IL depend strongly on the nature of the hydrophobic part PG of the copolymer than EG hydrophilic part. The present work demonstrates significant information on amphiphilic block copolymers for influencing temperature-sensitive copolymer CMT and micelle shapes in an IL, with potential applications in many arenas