Cellulose band assignments

Study of the crystal structure of polysaccharides, particularly of cellulose, has provided the main use for polarized infrared radiation in connection with carbohydrate spectra. Since this is another technique whereby band assignments can be made, the basic steps involved will be described in a simplified manner with reference to a polymer sample having uniaxial orientation. This is a common type of orientation, characteristic of fibers,... 

In Table 7.2, are presented the main FTIR bands assigned for components of starch/ cellulose filler films. 

Moreover, an absorption band near 1375 cm-i is detected and it is assigned to the CH bending vibration present in cellulose and hemicellulose chemical structures (Sim et al., 1998). The prominent band at 1044 cm-i is also associated with hemicelluloses and is attributed to the C-OH bending. Finally, a sharp band at 897 cm-i, which is typical of b-glycosidic linkages between the sugar units in hemicelluloses, was detected in the anomeric region (Sun et al., 2005). 

FTIR spectra of extracted wheat straw hemicellulose and cellulose do not exhibit this band (spectra not shown). From this point, the extracted wheat straw XRPP is also assigned to pectic substances. The intensity ratio of the bands i>as(COO ) at 1608 cm" and j (C 0) ester at 1740 cm corresponds to fully deesterified pectin and Me pectate... 

Table II lists the Raman peak positions for samples 4 and 11, which are typical of unbleached lignin-rich wood pulps. These peaks have been assigned in terms of contributions by cellulose and lignin. Raman contributions from hemicelluloses were expected to be broad and to occur at wavenumbers where cellulose contributions were detected. In Table II, certain bands are assigned to specific chemical-group vibrations. The assignment of bands to various groups in cellulose was based on literature [18]. The lignin-related assignments are based on the work described in this paper and the authors unpublished work.

A recent study of black spruce using FT-Raman with Nd YAG laser excitation (1,064 nm) proved successful (11). The goal in these studies was to be able to assign Raman features to the constituents of black spruce, cellulose, lignin, and hemicellulose. Black spruce is a soft wood. Any results obtainable could be applicable to all soft woods, and since soft woods are similar to hardwoods, the Raman bands observed could be assigned to cellulose and lignin. Hemicellulose contributions were not assignable because they were hidden under the cellulose bands. 

The structure of the cellulose hypophosphites synthesized has been confirmed by spectroscopy 69). The spectra erf cellulose hypophosphites show bands in the regions 2380-2440cm and l )0-1250cm" , assignable to the valence vibrations (rf the P—H and P-O groups, respectively. 

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