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In this study, the structure of the polycrystalline poly(l,4-phenyleneazine N,N-dioxide) was investigated by Scanning Electron Microscopy and related with the previously calculated molecular structure. Kinetics of polymerization of 1,4-dinitrosobenzene, prepared by both cryogenic UV photolysis and in vacuo deposition were measured by time-resolved FT-IR spectroscopy. Acquired data was analyzed by curve fitting with the standard Avrami-Erofeev and two-step consecutive reactions models. Activation parameters were calculated from Arrhenius and Eyring-Polanyi equations, for both models. The results obtained by using the two models, along with the goodness-of-fit parameters, were compared. It was shown that both bulk-based and reaction-based models can be used to adequately describe solid-state chemical reaction kinetics. Furthermore, a two-step consecutive reactions model is a suitable alternative to the most commonly used AvramiErofeev model.

The solid-state formation of azodioxide polymers from aromatic dinitroso compounds with different spacer groups was used as a model reaction for a comprehensive analysis that included bulk-based, mechanistic, and isoconversional kinetic methods. Dinitroso species were prepared in situ from azodioxides by UV cleavage under cryogenic conditions, after which their thermally induced conversion to azodioxides was followed by Fourier transform IR spectroscopy. The obtained data were used to calculate activation parameters and determine the influence of the spacer on the kinetics. Isoconversional models suggest a distribution of activation energies, pointing to an important (topochemical) effect of the local environment on the reactivity. In general, bulk-based and isoconversional kinetic models gave poorer fits but produced mutually consistent rate parameters. Similar energies and entropies of activation were obtained with all three approaches, suggesting that they all describe the same underlying physical phenomena; that is, the polymerization by bond-making is the dominant process.

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