In recent years we have had considerable success with the surface modification of amorphous and crystalline thermal plastic polymers using multi-end functional additives. In this proposal we explore two radically different situations in which these additives may have utility. Firstly, we address the situation of a thermoplastic matrix which is relatively incompatible with the additive. Secondly, we explore thermosetting polymers such as photecurable resins in which the additive is initially soluble, but becomes immiscible as curing proceeds. Neutron reflectometry will be used to determine the extent and nature of surface segregation in these systems with particular interest in the sharpness of the adsorbate-matrix interface. This has important implications for the durability of a surface modifying layer, since entanglement is necessary for the additive to be stable on the film surface.