Investigation of the Polymerization of 1,4-Dinitrosobenzene by Low-Temperature Infrared and UV Absorption Spectroscopy

Warming poly(1,4-phenyleneazine N,N-dioxide) at 50–65 °C and depositing under vacuum onto a CsI window at cryogenic temperatures gives 1,4-dinitrosobenzene, identified from infrared bands around 1520, 1120, 850, and 780 cm−1, which are characteristic for aromatic C-nitroso compounds. Thin films of 1,4-dinitrosobenzene were warmed from 32 K to room temperature in vacuo, and the polymerization reaction was shown to proceed through an intermediate, stable from 180 to 220 K. The intermediate shows C-nitroso- vibrational frequencies similar to those of the monomer but also has a strong band at 1260 cm−1 typical for an O-NN-O vibration in its infrared spectrum, assigned to the trans dimer of 1,4-dinitrosobenzene. Further warming of these films above 220 K results in formation of oligomers, and finally at temperatures from ca. 260 K to room temperature, complete polymerization occurs to regenerate poly(1,4-phenyleneazine N,N-dioxide). Similar results were obtained from UV absorption spectroscopy, which detected formation of an intermediate at ca. 180 K that on further wanning to room temperature gave the polymer. © 1993, American Chemical Society. All rights reserved.