Analytical pyrolysis of polyethyleneimines

Poly(ethylene imine) is a family of polymers with a high content of amine groups employed in various applications and widely investigated as CO2 adsorbents in carbon capture and sequestration. In this study, five branched polyethylenimines (PEIs) of different molecular weights were analysed by Py-GC-MS to gather information on the chemical structure of the principal thermal degradation products. All the PEIs produced pyrolysates with a similar chemical composition characterised by the occurrence of ethylenediamine, diethylenetriamine, piperazine, N-ethylaminepiperazine, pyrazine, 2-methylpyrazine, 2,3-dimethylpyrazine, 2- ethylpyrazine. Oligomeric ethylene polyamines were volatilised or evolved after chain scission of the PEI backbone. Pyrolysates also contained minor amounts of alkylated pyrroles, imidazoles, pyridines and other compounds that could not be identified. Pyrolysis products were formed at 300 ◦C, and their abundance increased markedly from 400◦ to 600◦C. Pyrolysis of PEIs at 500 ◦C in the presence of mesoporous silica favoured cyclisation and aromatisation, enhancing the production of alkylated pyrazines. These compounds are of potential interest in the food industry as flavour-enhancing additives.