Ion transfer through fluid-fluid interfaces plays decisive roles in many natural and industrial processes. In studies of Cu(II) transport by Permeation Liquid Membrane (PLM) system the carrier consists of a 1:1 mixture of alkylated aza-crown ethers and lauric or palmitic acid. In bulk organic phase the alkylated aza-crown ether are expected to form inverse micelles, due to the large hydrophilic crown ether head group. Depending on concentration crown ether molecules will be exchanged between the micellar structures in the organic phase and the adsorbed molecules at the liquid-liquid interface. The structure of the inverse micelles may play a role in possible ion transport and release from the aqueous phase into the organic phase. No structural parameters are available to characterize the aza-crown ether micelle. We therefore want to study the inverse micellar structure using SANS.