PYROLYSIS MECHANISMS OF O-(2-HYDROXYETHYL)CELLULOSES

Primary pyrolysis mechanisms for native cellulose are more universally applicable, which is illustrated by the analyses of the characteristi c pyrolysis product distributions of O-(2-hydroxyethyl)celluloses (HEC s) measured by in-source pyrolysis-ammonia chemical ionisation mass sp ectrometry (Py-CIMS). The extent of the thermal degradation via transg lycosidation, reverse aldolisation and E(i)-elimination mechanisms in these cellulose derivatives is strongly influenced by the presence of substituents and by their substitution positions. The transglycosidati on mechanism, which is the main thermal degradation pathway of cellulo se, is blocked if the 6-O-positions in the cellulose backbone are subs tituted. The formation of a series of polyethylene glycolaldehydes and polyethylene glycols is explained by the reverse aldolisation and E(i )-elimination mechanisms, respectively. The pyrolysis products of HECs have been identified by the determination of the number of hydroxyl g roups in the mass peaks, which was done by the comparison of NH3 and N D3 Py-CI mass spectra. The correlation between the pyrolysis product d istribution and substituents in HECs is illustrated by a multivariate analysis of the Py-CI mass spectra of 11 HECs, revealing structural in formation concerning the cellulose character and the average chain len gth of the substituents in the samples.