In cellulose materials, the cellulose II polymorph is often present either exclusively or in
conjunction with cellulose I, the natural cellulose. Moreover, in regenerated and
mercerized fibers (e,g., viscose and lyocell), natural cellulose adopts to the crystal
structure cellulose II Therefore, its detection and quantitation are important for a
complete assessment of such materials investigations. In the Raman spectra of such
materials, a band at 577 cm -1 is typically observed indicating the presence of this
polymorph. In the present study, to quantify the content of cellulose II, a calibration
method was developed based on the intensity of the 577 cm -1 peak relative to the
1096 cm -1 band of cellulose. For this purpose, in addition to pure cellulose I and
cellulose II samples (respectively, Avicel PH-101 and mercerized Avicel PH-101; hence
referred to as Avicel I and Avicel II), a set of five samples were produced by mixing
them in known quantities of Avicel I and Avicel II. The crystalline cellulose II contents of
the samples were calculated based on the X-ray crystallinity of mercerized Avicel I.
These seven samples were included in the calibration set and their Raman spectra
were obtained. Subsequently, Raman intensity ratios I 577 /I 1096 were calculated
by taking ratios of peak intensities at 577 and 1096 cm -1 . These ratios were plotted
against the % of crystalline cellulose II present in the calibration set samples and the
two were found to be linearly correlated (R 2 = 0.9944). The set-samples were also
analyzed using XRD which were then compared with the Raman method developed
here. Compared to XRD, the Raman method was found to be more sensitive at
detecting and quantifying cellulose II. Additionally, several cellulose II containing
materials were analyzed by the new Raman method.