Synthesis of polymer containing o-nitrobenzyl ether structure in the main chain

The polycondensation of nitrated xylenedihalides with diphenols was carried out under various conditions. The polycondensation of 2‐nitro‐1, 3‐xylylenedibromide (NXDB) with 4,4′‐isopropylidenediphenol proceeded in competition with the decomposition of polymer in the mixed solvent of tetrahydrofuran (THF) and dimethylsulfoxide (DMSO). The viscosity of the resulting polymer was markedly affected by the concentration of aqueous sodium hydroxide, reaction time, and reaction temperature. When dibromomethane was used as a solvent, the polycondensation proceeded very smoothly without the decomposition to give a higher reduced viscosity polymer than that in THF‐DMSO at 60°C. The polymer obtained in dibromomethane contained a very small amount of formal bonds determined from the 1H‐NMR spectrum. The formation of formal bonds seems to cause the molecular weight in increase. Furthemore, the polycondensation of NXDB with 2,2‐bis (4‐hydroxyphenyl) hexafluoropropane afforded high molecular‐weight polyether in dibromomethane. However, either high reaction temperatures or the high concentrations of aqueous potassium hydroxide solution casused the viscosity of the resulting polymer to decrease during the polycondensation in dibromomethane. The obtained polyethers with o‐nitrobenzyl groups showed relatively good solubility, and decomposed smoothly upon the irradiation with UV light. Therefore, these polymers might be useful for positive type photoresists.