Quantitative analysis of the transformation process of cellulose I → cellulose II using NIR FT Raman spectroscopy and chemometric methods

This paper reports a new, successful, utilization of NIR FT Raman spectroscopy for determinining the polymorphic transformation of native cellulose I into the allomorph cellulose II quantitatively. A rapid prediction of the transformation order is made possible by applying multivariate linear regression to the FT Raman spectral data of alkali-treated cellulose pulps. Simultaneously, changes in the crystallinity of cellulose I of these pulps were followed with respect to the lattice conversion process. The application of both multivariate quantification methods to the FT Raman spectra of the alkali-treated pulps yields a corrected polymorphic transformation order and enables the quantitative description to be made of the cellulose lattice conversion process as a system consisting of three participating forms of cellulose: crystalline cellulose I, amorphous cellulose and cellulose II.