Infrared spectra of the crystalline modifications of cellulose

Abstract

The bands due to stretching of OH groups of all four crystalline modifications of cellulose have been measured using a deuteration technique which enables crystalline regions to be studied independently of amorphous regions. Cellulose III prepared from cellulose I (III I) was found to be different from cellulose III prepared from cellulose II (III II). Similarly different cellulose IV's were obtained from celluloses I and II (IV I and IV II). However, the infrared spectra suggest that only one of these, namely, III I should be regarded as having a crystal structure distinctively different from those of cellulose I and II. Thus IV I and III II closely resemble celluloses I and II, respectively, while IV II shows a diffuse absorption and may well possess a disordered lattice. The bearing of these results on the crystal structures of celluloses I and II is discussed. The unit cells of celluloses III II and II are different, although their infrared spectra are very similar. These facts suggest that hydrogen bonding in these two forms is of the layer type in the (101) plane, though the possibility of hydrogen bonding in the (10 1) plane cannot be entirely eliminated.