The alternating copolymer of alkyl sorbates with oxygen was prepared by photopolymerization or thermal polymerization in the presence of oxygen. Methyl sorbate provided an alternating copolymer with oxygen on exposure to sunlight at room temperature. The yield and molecular weight of the obtained polymers depended on the polymerization conditions, e.g., the eater alkyl groups, the polymerization temperature, and the kinds of solvents. NMR spectroscopy confirmed the alternating copolymer structure containing labile peroxy bonds in their main chain. It was revealed by gel permeation chromatography that the polymers readily decomposed on heating. The molecular weight of the polymer was reduced to half value after 12 h at 60 degrees C, and the polymer immediately degraded to low molecular weight products at 120 degrees C.