Poly(ionic liquid) Latexes Prepared by Dispersion Polymerization of Ionic Liquid Monomers

Abstract

In this contribution, we report the facile preparation of vinylimidazolium-typed poly(ionic liquid) (PIL) latexes and nanoparticles via dispersion polymerization of ionic liquid monomers in aqueous solutions. A homologous series of vinylimidazolium-typed ionic liquid monomers with different alkyl tail length (C8−C18) were synthesized via quaternization of 1-vinylimidazole with corresponding n -alkyl bromides. Dispersion polymerization of these monomers was conducted at a monomer concentration of 50 g/L in aqueous solution at 70 °C without addition of further stabilizers. For ionic liquid monomers with sufficiently long alkyl chains (≥C12), PILs nanoparticles of 20−40 nm in diameter were found, which were self-stabilizing in aqueous media. In the same procedure, preparation of cross-linked PIL nanoparticles was performed in the presence of 10 mol % of divinylimidazolium-based cross-linker. The as-synthesized cross-linked PIL nanoparticles could be transferred into organic solvents, such as polar DMF, and nonpolar toluene after anion exchange with lithium bis(trifluoromethylsulfonyl)imide. This dispersion polymerization requires no dispersing agent and potentially enables a large scale synthesis of PIL nanoparticles in both aqueous and organic solutions. The application spectrum of this unique type of organic nanoparticles is expectedly broad; e.g., the particles are useful as powerful binders and dispersants for coatings and as colloidal templates.