It is proposed to use small-angle neutron scattering (SANS) to investigate in detail the binary phase diagram between 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][Tf2N]) and 1-dodecyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C12MIM][Tf2N]) in order to provide information on the organisation of one ionic liquid within the other. The work will be carried out by preparing one of the ionic liquids in perdeuterated form and taking advantage of the contrast variation that this offers. The proposal is made following preliminary Xpress experiments on Sans2d and is complementary to an application for reflectivity measurements submitted this round. The results will be complemented by those from laboratory experiments using surface tension and viscosity measurements to provide a very detailed picture of the binary behaviour of this system.