F.t.-ir. spectra of algal, bacterial, cotton, ramie, and wood celluloses, obtained in the second-derivative mode, have improved resolution. The spectra support the hypothesis that the crystalline structures of these celluloses can be divided into algal-bacterial and cotton-ran&-wood types. Bands that differ in the spectra of the two types are different from those sensitive to the change cellulose I-+11.
INTRODIJCI?ON
The structures of the two major polymorphs (I and II) of cellulose have been studied extensively, but less attention has been given to the question of allomorphy within the cellulose I (native cellulose) family. An early X-ray diffraction study' of algal, bacterial, cotton, and ramie celluloses found significant differences in the parameters of the unit cell and differences were observed also in electron diffraction studies2p3. Solid-state n.m.r.4-8, Raman spectroscopicg, and electron diffraction studiesi showed that the crystalline structures of native celluloses can be classified into algal-bacterial and cotton-ramie-wood pulp typess. Wiley and Atalla proposed that these two types have similar conformations but are packed in different lattices, whereas otherslo have suggested that the differences within the cellulose I family are derived from the size of the unit cells.
1.r. spectroscopy was one of the earliest techniques used to examine the crystalline nature of the celluloses. Marrinan and Mann" and Liang and Marchessault" obtained two types of band patterns in the OH and CH stretching regions (3604_2SOO cm-i) for native celluloses. Marchessault and Liangi3 extended the study to the region 1700-640 cm-i. Despite some of the spectra having been recorded" on samples at the temperature of liquid nitrogen, the bands tended to be broad and poorly resolved. However, use of the second-derivative model4 can assist in resolving the spectra of celluloses. Second-derivative spectra of celluloses obtained from algae, bacteria, ramie, cotton, and wood are now reported.