Various blends of polymers are disclosed, comprising oligopeptide functionalised polymers such as polyisobutylene and polystyrene. Mono-functionalised and di-functionalised polymers (each containing 0 to 5 peptide units beyond its terminal amide group) may be blended with each other and / or with non-functionalised polymers to produce blended compositions. Such compositions are of use, for example, in vibrations dampers. Certain blends also exhibit self-healing properties.