Polymeric vesicles and micelles obtained by self-assembly of ionic liquid-Based block copolymers triggered by anion or solvent exchange

The solution properties of IL-based block copolymers (IL BCs) of the type PAm-b-PIL-1Br, PMAA-b-PIL-2Br, and PMAA-b-PIL-3Br, where PIL, PAm and PMAA stand for polymeric ionic liquid, poly(acrylamide), and poly(methacrylic acid), respectively, are manipulated and made to self-assemble into nanoparticles in water or in organic media. This can be achieved not only by simply exchanging the bromide (Br^-) counteranion of IL blocks for ^-N(SO ₂CF₃)₂, but also by the choice of a selective solvent or by methylation of the hydrophilic PMAA blocks into hydrophobic poly(methyl methacrylate) (PMMA) ones. Investigations into the behavior of self-assembled IL BCs aggregates by 1H NMR spectroscopy, light scattering and transmission electron microscopy evidence that anion or solvent exchange or chemical modification induce the formation of polymeric vesicles referred to as polymersomes, for IL BCs of hydrophilic mass fraction (f) of around 40. The size and shape of the self-assembled aggregates formed can be altered by changing the composition of the blocks or by a partial exchange of the anion. In addition, the anion sensitivity of these IL BCs occurs reversibly. For instance, anion exchange of the PIL block, from Br^- to ^-N(SO ₂CF₃)₂ leads to a vesicular morphology consisting of ^-N(SO₂CF₃)₂-based IL blocks as the hydrophobic membrane stabilized by water-soluble PAm (or PMAA). As for PAm₁₃₅-b-(PIL-1N (SO₂CF₃)_{2 12} IL BC possessing a hydrophilic mass fraction higher than 45, it is found to self-assemble into spherical polymeric micelles.