Study of the interaction of a poloxamer with short and long alkyl chain imidazolium ionic liquids.

The ethylene oxide (EO)/propylene oxide (PO) triblock copolymers (EO)m-(PO)n-(EO)m, also known as poloxamers, self-assemble in aqueous solution due to the differences in hydrophobicity between EO and PO. Both the overall length of the blocks and their relative lengths in the copolymer impact self-assembly. Even though poloxamers lack charge, they respond to the presence of salts, including ionic liquids (ILs). Here, the response of poloxamer 188 to 1-alkyl-3-methylimidazolium chlorides having long and short alkyl chains was studied by small-angle neutron scattering. The dilute state of both the polymer and ILs was studied, with the IL concentrations being below published critical micelle concentrations. The goal was to probe initial stages of self-assembly. The results demonstrate a clear interaction between the long chain imidazolium chloride and the poloxamer that is surfactant-like, which is not observed for the short alkyl chain salt.