How multiple noncovalent interactions regulate the aggregation behavior of amphiphilic triblock copolymer/surface-active ionic liquid mixtures

Abstract

Amphiphilic block copolymers/ionic liquids mixtures have been emerging as a new class of ‘chemical entity’ with numerous advanced applications. However, interaction mechanism governing the aggregation and the microstructure of aggregates are still far from full understanding. Herein, the role of noncovalent interactions in regulation of aggregation behaviors of mixtures of Pluronic F127 and surface-active ionic liquids, i.e. CnmimBr, CnPyBr and CnMPB is investigated by DLS, cryo-TEM, NMR and molecular dynamics simulation. The interaction modes between F127 and SAILs are remarkably dependent on the concentration and cationic headgroup of SAIL. At low SAIL concentration (<CMC), mixed micelles mainly composed of F127 with some SAIL cations embedded into micelles are formed, which was primarily driven by hydrophobic interaction. However, the residence of CnmimBr cations in micelles is quite different from that of CnPyBr and CnMPB cations due to its distinctive hydrogen bonding with PEO segment of F127. Upon further addition of SAILs (CSAILs > CMC), gradual disintegration of F127-rich micelles was observed due to the enhanced repulsive electrostatic force at micellar core-corona interface, accompanying with the re-formation of two types of micelles: one consisting of pure SAILs and one that SAIL micelles bound with F127 monomers via hydrogen bonding and/or hydrophobic interactions. This work provides new insight into the aggregation mechanism of these complex systems and will be helpful to rational tailoring innovative copolymers /IL-based system for specific applications.