Correlations of Apparent Cellulose Crystallinity Determined by XRD, NMR, IR, Raman, and SFG Methods

• Published in: Advances in polymer science Vol. 271; pp. 115 - 131
• Main Authors: Lee, Christopher, Dazen, Kevin, Kafle, Kabindra, Moore, Andrew, Johnson, David K., Park, Sunkyu, Kim, Seong H.
• Format: Book Chapter Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.01.2016
• Series: Advances in Polymer Science
• Subjects: biofuels (including algae and biomass), bio-inspired, membrane, carbon sequestration, materials and chemistry by design, synthesis (self-assembly); Crystallinity index; Infrared spectroscopy; INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Nuclear magnetic resonance; Raman spectroscopy; Sum frequency generation spectroscopy; Wood pulp; X-ray diffraction
• ISBN: 3319260138; 9783319260136
• ISSN: 0065-3195; 1436-5030
• DOI: 10.1007/12_2015_320

Although the cellulose crystallinity index (CI) is used widely, its limitations have not been adequately described. In this study, the CI values of a set of reference samples were determined from X-ray diffraction (XRD), nuclear magnetic resonance (NMR), and infrared (IR), Raman, and vibrational sum frequency generation (SFG) spectroscopies. The intensities of certain crystalline peaks in IR, Raman, and SFG spectra positively correlated with the amount of crystalline cellulose in the sample, but the correlation with XRD was nonlinear as a result of fundamental differences in detection sensitivity to crystalline cellulose and improper baseline corrections for amorphous contributions. It is demonstrated that the intensity and shape of the XRD signal is affected by both the amount of crystalline cellulose and crystal size, which makes XRD analysis complicated. It is clear that the methods investigated show the same qualitative trends for samples, but the absolute CI values differ depending on the determination method. This clearly indicates that the CI, as estimated by different methods, is not an absolute value and that for a given set of samples the CI values can be compared only as a qualitative measure.