EPR and ESEEM Identification of Free Radicals and Molecular Structure of the Oligomers Formed During Polycondensation of 1-Chloro-4-nitrobenzene with Sodium Sulfides in N-Methyl-2-pyrrolidone

The synthesis of derivative of poly (4-hydrazo-diphenylenedisulfide) by reaction of 1-chloro-4-nitrobenzene with sodium sulfide and disulfide in N-methyl-2-pyrrolidone leads to oligomeric products with average molecular weight of the homogeneous chains 1182 g/mol and 690 g/mol, respectively. The mechanisms of the reactive intermediates polycondensation reaction are described. The products were characterized by IR, 'H NMR, and EPR spectroscopy and by elemental analysis. The final amorphous oligomer products contain mostly diamagnetic species and about 1% ofparamagnetic species. The latter produce strong isotropic EPR signal at g = 2.0025 from free radical with concentration of about 10 1 8 radicals/gram. Pulsed EPR spectroscopy allowed identifying the radical by analysis of the electron spin echo envelope modulation spectrum. The radical is localized on the carbon atom of the C=O-group of the N-methyl-2-pyrrolidone moiety with broken internal C-N bond of the lactam ring.