7-Iodo-1-oxaspiro[2.5]octa-5,7-dien-4-one undergoes melt polymerization to yield poly(oxy-4-iodo-1,2-phenylene-oxymethylene). The polymerization involved a nucleophilic attack of the terminal hydroxy group of the growing polymer chain at the methylene carbon in oxirane followed by cleavage of the oxirane ring and simultaneous aromatization of cyclohexadienone to generate a new phenol to continue the polymerization.