Siloxanes are a premier example of an inorganic polymer, even though they have extensive organic substituents.  Their backbond is composed of alternating silicon and oxygen atoms, i.e. Si-O-Si-O...  The silicon atoms bear two substituents, usually methyl as in the case of polydimethylsiloxane.  Some uncommon but illustrative inorganic polymers include polythiazyl ((SN)x) with alternating S and N atoms, and polyphosphates ((PO)).