Effect of Protic Ionic Liquid Nanostructure on Phospholipid Vesicle Formation

Abstract

The formation of bilayer-based lyotropic liquid crystals and vesicle dispersions by phospholipids in a range of protic ionic liquids has been investigated by polarizing optical microscopy using isothermal penetration scans, differential scanning calorimetry, and small angle X-ray and neutron scattering. The stability and structure of both lamellar phases and vesicle dispersions is found to depend primarily on the underlying amphiphilic nanostructure of the ionic liquid itself. This finding has significant implica-tions for the use of ionic liquids in soft and biological materials and for biopreservation, and demon-strates how vesicle structure and properties can be controlled through selection of cation and anion. For a given ionic liquid, systematic trends in bilayer thickness, chain-melting temperature and enthalpy in-crease with phospholipid acyl chain length, paralleling behaviour in aqueous systems.