Rate of Molecular Exchange through the Membranes of Ionic Liquid Filled Polymersomes Dispersed in Water

Abstract

The permeation of 1-ethyl-3-methylimidazolium ([EMIM]), 1-butyl-3-methylimidazolium ([BMIM]), and 1-butylimidazole through the bilayer membranes of nanoemulsion-like polymersomes was investigated by nuclear magnetic resonance spectroscopy (NMR) techniques. 1,2-Polybutadiene-b-poly(ethylene oxide) (PB–PEO) polymersomes in the ionic liquid (IL) 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][TFSI]) were prepared by a cosolvent method and then migrated to the aqueous phase, which is not miscible with the IL, at room temperature. In this way stable, nanoscopic domains of the IL (average diameter ca. 200 nm) were dispersed in water. Two similarly sized molecules, charged [EMIM] and neutral 1-butylimidazole, were employed as tracer molecules, and proton NMR (1H NMR) and pulsed-field-gradient NMR (PFG-NMR) experiments were conducted. Furthermore, transient 1H NMR was used with [BMIM] to estimate how rapidly the charged molecules can go through the hydrophobic membrane into the polymersome i...