A novel self-healing supramolecular polymer system

Utilising supramolecular π–π stacking interactions to drive miscibility in two-component polymer blends offers a novel approach to producing materials with unique properties. We report in this paper the preparation of a supramolecular polymer network that exploits this principle. A low molecular weight polydiimide which contains multiple π-electron-poor receptor sites along its backbone forms homogeneous films with a siloxane polymer that features π-electron-rich pyrenyl end-groups. Compatibility results from a complexation process that involves chain-folding of the polydiimide to create an optimum binding site for the π-electron-rich chain ends of the polysiloxane. These complementary π-electron-rich and -poor receptors exhibit rapid and reversible complexation behaviour in solution, and healable characteristics in the solid state in response to temperature. A mechanism is proposed for this thermoreversible healing behaviour that involves disruption of the intermolecular π–π stacking cross-links as the temperature of the supramolecular film is increased. The low Tgsiloxane component can then flow and as the temperature of the blend is decreased, π–π stacking interactions drive formation of a new network and so lead to good damage-recovery characteristics of the two-component blend.