Effect of polyvinylpyrrolidone on the microstructure of 1-butyl-3-methylimidazolium tetrafluoroborate/Triton X-100/cyclohexane microemulsions

The effect of the polymer polyvinylpyrrolidone (PVP) on the microstructure of reverse microemulsions consisting of the ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF4), the surfactant Triton X-100 and the component cyclohexane was investigated in the present work. The study of the phase behavior revealed that the existence region of the microemulsion state is remarkably decreased by the addition of PVP. Conductivity measurements showed that the threshold of electrical percolation is also slightly decreased with increasing PVP content, indicating an increase of the attractive interaction between the microemulsion droplets. The microemulsion droplets were gradually swollen by both, bmimBF4 and PVP addition, and thereby the viscosity of the microemulsion solution was slightly increased. FTIR and NMR measurements revealed that there is no special interaction between the added PVP and Triton X-100, that is, PVP was only solubilized inside the polar IL-core of the microemulsion droplets.