Investigation of the initiatory reactivity of polynitro-amines and-arenes via X-ray photoelectron spectroscopy

Abstract

The initiation reactivity of a wide range of polynitro compounds has been assessed via X-ray photoelectron spectroscopy (XPS). These compounds include nitramines (epsilon-CL20, beta-CL20, BCHMX, TTAZ), six beta-CL20/BCHMX co-agglomerates (CACs) and eight highly thermostable "genuine " polynitroarenes (HNBP, ONT, NONA, DODECA, TENN, BTX, TPT and TACOT Z), all of which exhibit primary homolysis of the trigger bond. The binding energies (Ebind) of N 1s and O 1s electrons have been analyzed in relation to the enthalpy of formation, impact and electric-spark sensitivity, detonation velocity and crystal density. Higher Ebind values in both elements correlate with increasing enthalpy of formation and impact sensitivity. Electric spark sensitivity is directly proportional to O 1s Ebind. Detonation velocity increases with Ebind; however, beta-CL20/BCHMX composites and the O 1s Ebind values of polynitro-polyazarenes (TACOT Z-BTX-TPT) show inverse trends. The relationship of N 1s Ebind with the longest X-NO2 bond ( X = C or N) in the molecule reflects nitro-group interactions with the rest of the molecule, whereas O 1s Ebind is shaped by crystal packing. Relationships between Ebind and crystal density have also been found and discussed. Additional correlations between N 1s Ebind values and FTIR symmetric N-O stretching support the identification cocrystals in CACs. These findings highlight XPS as a valuable tool for probing initiation reactivity and intermolecular behavior in energetic materials.