The influence of reaction conditions in aqueous HCN polymerization on the polymer thermal degradation properties

- HCN polymers were synthetized using different experimental conditions.
- The HCN polymers were studied by TGA, DTG, DSC and TG-MS.
- New macromolecular structures are suggested for the HCN polymers.
- The thermal studies might help to explain remote data from extraterrestrial organics.
- The DTG and DSC curves are useful to distinguish similar samples by other techniques.

The influence of the reaction conditions in the synthesis of HCN polymers in water at low temperature has been analyzed. The thermal stability of the HCN polymers obtained from aqueous solutions and under inert atmosphere was evaluated by thermogravimetry and differential scanning calorimetry (TG-DSC) techniques. In addition, in situ mass spectrometry (MS) was employed to investigate the characteristic functional groups of the decomposition residues at different temperatures. The structural complexity of this polymeric solid is reflected in the DTG curves, hence a peak deconvolution procedure was applied. The deconvolution revealed that the complex thermal decomposition of HCN samples occurs in multiple overlapping processes, not perceptible in the curves of weight loss, which were influenced by the differences in the polymerization conditions. In addition, the great molecular diversity found in this macromolecular system is also maintained in the DSC thermograms. The deconvolution of the DTG curves provided a strong fingerprint of the HCN polymers together with the DSC as a complementary mark. Although the full structures of the HCN polymers are not yet revealed, the deconvolution of the thermal curves provides an excellent signature for comparative purposes. The profile of the DTG and DSC curves can not only help design HCN polymers with specific properties but also help interpret remote-sensing observations of comets, meteorites and samples from different planetary environments.