The present invention is directed to a rubber composition comprising: a functionalized elastomer comprising a polymeric backbone chain derived from a monomer comprising at least one conjugated diene monomer and optionally at least one vinyl aromatic monomer; and a functional group bonded to the backbone chain, the functional group comprising a multidentate ligand capable of complexing with a metal ion; and an encapsulated metal salt.The invention is further directed to a pneumatic runflat tire comprising a sidewall insert, the insert comprising the rubber composition.