Polymer-surfactant mixtures are extensively used in a wide range of domestic, industrial and technological applications. This proposal is part of a collaboration between Oxford / CCLRC and Unilever to study the adsorption of polymer / surfactant mixtures at interfaces and to understand and manipulate the major factors which control partitioning to different interfaces. We request here beam time on LOQ to complete a series of measurements on the adsorption of PEI / SDS and modified PEI / SDS mixtures at the solid-solution interface. To date, these measurements have produced some interesting and significant results, and which will have some substantial impact upon detergency type applications.