Structural investigations using X-ray diffraction on four side-chain liquid crystal polymers with the same mesogenic units but different backbones are described. An S*(C) phase was identified in all of them. Three of the polymers exhibit an unusual phase with a superlattice structure below this S*(C) phase. A simple model of the packing in this phase is proposed to explain the formation of the superlattice. The effects of varying the polymer backbone on the stability of this phase are also discussed.