Synthesis of cis- and trans-polyisoprene adduct with nitrogen dioxide (NO2/N2O4 mixture) and a study of the thermal stability of the adduct

Tetrahydrofuran solutions of cis- or trans-polyisoprene react rapidly with a NO2/N2O4 mixture without crosslinking and gelation of the solution (as happens in other solvents) and with formation of a dinitro-adduct (nitro-cis-PIP and nitro-trans-PIP) as the main product. The chemical structure of the adduct was analyzed by FT-IR and UV spectroscopy revealing that species other than the nitro (-NO2) groups are also present in the adduct, like for instance the nitrate group (-ONO2). The thermal stability of the adduct was studied by the thermogravimetric analysis (TGA-DTG) combined with differential thermal analysis (DTA). The initial decomposition of the adduct is exothermic and the release of heat reaches its maximum at about 200 °C and the completion of the exothermic decomposition occurs at about 325 °C. The amount of nitro groups present in the adduct was determined by the TGA-DTG. The decomposition of the adduct was also followed by the TGA-FTIR analytical technique and a certain number of volatile and gaseous species were detected ranging from mixtures of nitrogen oxides and nitroalkanes to NH3, HCN and CH4. The adduct nitro-cis-PIP and nitro-trans-PIP yield a carbon foam even at 400 °C which can be defined as a crosslinked vitreous carbon foam which was studied by FT-IR spectroscopy.