We have recently prepared and studied the surface properties of some well-defined multi-end functional polyethylenes. Whilst most of our surface studies indicate that these functional additives are miscible with the bulk, our initial SANS experiments showed phase separation into two domains, which have nearly identical crystallisation temperatures. We believe that this apparent contradiction may be due to incompatibility between the perdeuterated matrix used in SANS and the additive, which is more severe than for the surface studies in which the matrix was hydrogenous. In both cases the same partially deuterated additives were used. Here we propose to resolve the issue by repeating some key SANS experiments in exactly the same matrix as was used in the surface studies.