Using coarse-grained molecular dynamics to understand the effect of ionic liquids on the aggregation of Pluronic copolymer solutions


This study is aimed to enhance the understanding of the interaction between ionic liquids (ILs) and non-ionic Pluronic triblock copolymers in aqueous two-phase micellar systems (ATPMS) used for the selective separation/purification of hydrophobic biomolecules. The ILs allow a precise control of the cloud point phase separation temperature (CPT), particularly important when the stability of the molecule is highly dependent on temperature. The effect of choline-based ILs, with two different counter-anions, chloride and hexanoate, was evaluated using molecular dynamics simulations (MD) for F-68 and L-35 Pluronic aqueous solutions. The simulations revealed the role played by the anions during the Pluronic self-assembly, with choline chloride hindering Pluronic aggregation and the choline hexanoate favouring micelle formation and coalescence, in agreement with the experimental data. A detailed study of the accessible surface area of Pluronic showed a progressive dehydration of the Pluronic hydrophilic micelle corona in choline hexanoate mixtures promoting inter-micelle interactions and, consequently, micelle coalescence. With the addition of choline hexanoate, it was observed that the hydrophilic segments, which form the micelle corona, twisted towards the Pluronic micelle core. The electrostatic interaction is also shown to play a key role in this IL-Pluronic aqueous solution, as the hexanoate anions are accommodated in the Pluronic micelle core, while the choline cations are hosted by the Pluronic micelle corona, with the ions interacting with each other during the self-assembly process. In addition, a comparison study of F-68 and L-35 aqueous solutions shows that the IL impact depends on the length of the Pluronic hydrophilic segment. This work provides a realistic microscopic scenario of the complex interactions between Pluronic copolymers and ILs.

subject category

Chemistry, Physical; Physics, Atomic, Molecular & Chemical


Perez-Sanchez, G; Schaeffer, N; Lopes, AM; Pereira, JFB; Coutinho, JAP

our authors


This work was developed within the scope of the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020 & UIDP/50011/2020, financed by national funds through the FCT/MEC and when appropriate co-financed by FEDER under the PT2020 Partnership Agreement. The authors acknowledge the research contract under the project CENTRO-01-0145-FEDER-000005: SusPhotoSolutions: Solucoes Fotovoltaicas Sustentaveis. G. Perez-Sanchez and N. Schaeffer acknowledge the national funds (OE), through FCT - FundacAo para a Ciencia e a Tecnologia, I. P., in the scope of the framework contract foreseen in the numbers 4, 5 and 6 of the article 23, of the Decree-Law 57/2016, of August 29th, changed by Law 57/2017, of July 19th. A. M. Lopes acknowledges the support from the State of SAo Paulo Research Foundation (FAPESP/Brazil, processes #2017/10789-1 and #2018/10799-0). J. F. B. Pereira also acknowledges FAPESP through the project 2014/16424-7.

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