Polymeric Vesicles and Micelles by Self-assembly of Ionic Liquid-based Block Copolymers Triggered by Anion or Solvent Exchange
Résumé
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, polyacrylamide 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-) counter-anion of IL blocks for - N(SO2CF3)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 behaviour 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(SO2CF3)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.