Some aspects of the surface and bulk chemistry of cellulose nitrates as studied by ESCA and other spectroscopic techniques

Abstract

x-ray photoelectron spectroscopy (E.S.C.A.) has been used to investigate the surface chemistry of cellulose nitrates. The heterogeneous nitration and denitration of cellulose nitrates has been studied as a function of time and temperature and important conclusions have been drawn on the complex equilibria established at the surface. (^13)C solution state n.m.r. has been employed also in these reactions to monitor the bulk chemistry; partial degrees of substitution established at individual sites of a β-D-anhydropyranose ring. Correlations are drawn between these partial DOS's and the mean d(110) interchain spacings in cellulose nitrates, and show evidence for possible morphological changes. The nature of the nitrating species in a technical acid mix has been alluded to by the use of laser Raman spectroscopy. Evidence exists for the species being the nitronium ion, NO(_2)(^+). The X-ray induced and thermal degradation of cellulose nitrates, both surface and bulk has been addressed by the use of ESCA, FAB/SIMS and (^13)C n.m.r. New information on the build up of degradation products at the surface is postulated by the formation of an oxime structure, with concomitant in creases in carbonyl and ester functionalities. Conclusions are given which suggest that electromagnetically induced de gradation is a surface phenomenon, whereas thermal degradation IS predominantly bulk orientated. The use of trifluoroacetic anhydride as a hydroxyl tagging agent has been investigated on cellulosic materials. Incomplete esterification of the hydroxyl groups occurs.