Oligomers are commonly added to adhesives in order to improve surface tack properties. However, it is also important that the oligomers do not adversely affect the solid (glassy or crystalline) domains in the elastomer. Subtle changes to the stability of these domains could be responsible for the gradual ageing and loss of mechanical properties of the adhesives. In order to characterise this and acutely sensitive method is required to measure the interaction between oligomers and materials that are representative of the glassy domains. Here we propose to use neutron reflectivity to analyse swelling and interfacial broadening of fin polystyrene films, which are a one-dimensional analogue of the glassy domains present in adhesives.