Microstructural micellar transition in bile salt-ionic liquid mixed systems in water: a DLS and SANS study

Due to the potential use and widespread applications of mixed micelles, herein we report the formation of rod-like micelles from the mixtures of a surface active ionic liquid (IL) and bile salt (BS). Mixed micelles of sodium deoxycholate (NaDC) and sodium cholate (NaC) with 1-decyl-3-methylimidazolium chloride (C(10)mim Cl) have been assessed by spectral and scattering techniques. These bile salts display electrostatic and hydrophobic interactions with the IL. The incorporation of bile salts in IL micelles leads to an increase in solution viscosity suggesting micellar growth and transitions. These observations are confirmed by dynamic light scattering (DLS) and further supported by small angle neutron scattering (SANS). The unusual viscosity behaviour is observed by altering the solution pH. NMR provided information on deeper penetration of NaDC molecules in IL micelles. Such a bile salt induced sphere-to-rod micellar transition further modulated by pH is of its first kind in an IL-bile salt mixed system.