Abstract
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.
Highlights
A ROMATIC C-nitroso compounds have proven to be a useful model system for the investigation of chemical reactions in the solid state.[1,2,3]They exist in two different forms, as nitroso compounds, and E- or Zazodioxy compounds.[4,5] In the solid state, most aromatic C-nitroso compounds appear in the azodioxy form, but can be converted to stable or metastable monomeric forms by dissolution in organic solvents, heating, or by UV irradiation at cryogenic temperatures.[5]
The first intermediate observed by IR spectroscopy is the Z-azodioxy isomer, but further warming causes the irreversible rearrangement to the E-isomer, and the formation of the stable polymer
The observable folding which appears in larger crystalline particles is expected from the extent of molecular folding found in PNND by calculation.[6]. Such a robust structure is a consequence of regular molecular arrangement and as such could be a suitable starting material for the study of the photochemical and thermochemical reaction mechanisms in the solid state
Summary
A ROMATIC C-nitroso compounds have proven to be a useful model system for the investigation of chemical reactions in the solid state.[1,2,3]They exist in two different forms, as nitroso compounds (monomers), and E- or Zazodioxy compounds (dimers or polymers).[4,5] In the solid state, most aromatic C-nitroso compounds appear in the azodioxy form, but can be converted to stable or metastable monomeric forms by dissolution in organic solvents, heating, or by UV irradiation at cryogenic temperatures.[5]. Repolymerization.[1,2] repolymerization after photolysis depends on the regularity of the crystal structure of the starting polymer.[1] In this work, we present a morphological investigation of the polymeric material, complemented with isothermal determination of activation energies for the polymerization under cryogenic conditions.
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