A FOURIER-TRANSFORM INFRARED SPECTROSCOPIC ANALYSIS OF THE CHARACTER OF HYDROGEN-BONDS IN AMORPHOUS CELLULOSE

Hydrogen-bonding formation in amorphous cellulose was characterized by the analysis of Fourier transform infra-red (FT i.r.) spectra. Films of regioselectively substituted methylcelluloses were used to model co mponents of amorphous cellulose. An artificial infra-red (i.r.) spectr um for amorphous cellulose was quantitatively synthesized by a suitabl e mathematical combination of the i.r. spectra obtained for the methyl cellulose model compounds. A comparison between the i.r. spectrum for an amorphous film blend composed of 2,3-di-O- and 6-O-methylcelluloses and the artificial spectrum showed an almost complete overlap in the OH frequency region, indicating that after mixing there is no interact ion between the OH groups of each component in the film blend. In othe r words, the OH bands in the artificial spectrum were considered to be simply a sum of hydrogen-bond absorptions contributed by each individ ual spectrum. The artificial spectrum was then compared to an experime ntal spectrum for an amorphous cellulose sample. The difference betwee n the two spectra (real-artificial) was then analysed and interpreted by using results from a previous i.r. study on hydrogen bonding in alc ohols and our own assumptions about the probable hydrogen bonds formed in amorphous cellulose. These analyses revealed that while the hydrox yl groups at the C(2) and C(3) positions in a glucose repeating unit a re isotropically involved in intermolecular hydrogen bonding in amorph ous cellulose, the hydroxyl group at the C(6) position is favourably e ngaged in an interchain hydrogen bonding that results in the formation of a crystalline state. Thus we conclude that amorphous cellulose mig ht be composed, at least to some extent, by randomly distributed domai ns formed by intermolecular hydrogen bonds.