Polymerized ionic liquid as stabilizer in aqueous emulsion polymerization enables a hydrophilic-hydrophobic transition during film formation

摘要

Polymerized ionic liquid (PIL) nanoparticles are for the first time applied as sole stabilizers in aqueous emulsion polymerization and reveal an astonishing and unexpected behavior. In a well-dispersed state, the PIL nanoparticles serve as an unexpectedly effective stabilizer for polystyrene dispersions, enabling solids content of greater than 40%. However, the same PIL as dry powder is hydrophobic and, in accordance with Bancroft's rule, unable to stabilize aqueous dispersions. This ambivalent behavior of PIL is extremely beneficial for the application of aqueous dispersions because, as desired for decades, the hydrophilic dispersed state during synthesis turns hydrophobic in the dried state during application of the polymer. Polymerized ionic liquids (PILs) are a new class of very effective colloidal stabilizers for emulsion polymerization. In contrast to state of the art emulsifiers for latex particles, PILs have the decisive advantage that they do not increase the hydrophilicity of the final polymeric product but act, due to their inherent properties, in the opposite direction and increase the hydrophobicity.