Polycondensation of sodium tetrazodiphenyl naphthionate and pyromellitic dianhydride under microwave irradiation and the performance of the third‐order nonlinear optics

Sodium tetrazodiphenyl naphthionate and pyromellitic dianhydride were polycondensed under microwave irradiation and oil‐bath heating. The resultant poly(amic acid) was imidized in the solid phase by microwave irradiation and oil‐bath heating. The effects of the reaction temperature, the concentration of monomers, the monomer ratio, and the microwave irradiation time on the conversion, intrinsic viscosity, and third‐order nonlinear optical (NLO) coefficient of the polymer were investigated. The results showed that the polycondensates had high third‐order NLO coefficients (χ(3) = 1.476 × 10−12esu) and very fast time responses (15.79 ps). The χ(3) values of the polycondensates under microwave irradiation were higher than those of conventional thermopolymerization.