Effect of ionic liquids on microstructures of micellar aggregates formed by PEO–PPO–PEO block copolymer in aqueous solution

•Aqueous mixed systems of Pluronics® (F127) with various pyridinium based ILs were studied.•Size and shape for micelles of F127 in aqueous solutions of ILs were measured by SANS and DLS.•The interactions between PEO/PPO with ILs were checked by 1H NMR and viscosity.•Upon addition of ILs, an enhancement in CMC and reduction in micellar size of F127 were found.•Effect of alkyl chain length, head group, anions and concentration of ILs has been discussed. Effect of ionic liquids (ILs) viz. pyridinium, picolinium and imidazolium halide on the micellization and the structure of poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO–PPO–PEO) triblock copolymer, F127 in aqueous solution has been studied by small angle neutron scattering (SANS) and dynamic light scattering (DLS) measurements. The interaction information between ILs and PEO/PPO has been explored by using 1H NMR and viscosity measurements. The micellar structural parameters are obtained as a function of variation in alkyl chain length, cationic head group and concentrations of ILs by fitting the SANS data with model composed of core–shell form factor and a hard sphere structure factor of interaction. Addition of ILs is found to decrease the micellar core radius, aggregation number and hard sphere radius of F127 micelles. The effect of concentration, chain length and head groups of ILs also have been studied.