Polymer and Organic Light Emitting Device A polymer comprising a repeat unit of formula (I a), (I b) or (Ic): (Formulae (Ia), (Ib), (Ic)) wherein M is a metal; R is a backbone repeat group; n is 1 or 2; Sp is a spacer group; w is 0 or 1; L1 and L2 are mono- or bidentate co-coordinating groups; ---- represents a second metal to ligand bond in the case where L1 or L2 is a bidentate ligand and at least one of L1 and L2 is substituted with group of formula (II) (Formula (II)) wherein m is 0 or 1; each Ar1, Ar2 and Ar3 is aryl or heteroaryl. The polymer may be used as an emissive material in an organic light-emitting device.