Solid-state polymerization of 7,7,8,8-tetrakis(methoxyethoxycarbonyl,)quinodimethane (1) was investigated in vacuo by irradiation using a high-pressure mercury lamp at 30 degrees C. The polymerization of I in the solid state took place in very slow rate and reached to a complete conversion at 37 days. UV irradiation of I crystals formed a diradical dimer of I as a reactive intermediate, coupling reaction of which afforded a corresponding polymer with a molecular weight of >20 000. When the UV-irradiated I crystals were dissolved in a degassed solvent, a 1,1,2,2,9,9,10,10-octa(methoxyethoxycarbonyl)[2.2]paracyclophane is formed and it call react with molecular oxygen in air and/or dissolved oxygen in solvents to afford a peroxide-bridged cyclophane. The molecular packing mode of 1 in the crystals was investigated by X-ray crystal structure analysis, and the low polymerization reactivity of I in the solid state and the formation of 1,1,2,2,9,9,10,10-octa(methoxyethoxycarbonyl)[2.2] paracyclophane were discussed on the basis of the molecular packing mode.