Chapter

Cellulose Chemistry and Properties: Fibers, Nanocelluloses and Advanced Materials

Volume 271 of the series Advances in Polymer Science pp 115-131

Date:

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

  • Christopher LeeAffiliated withDepartment of Chemical Engineering and Materials Research Institute, Pennsylvania State University
  • , Kevin DazenAffiliated withDepartment of Chemical Engineering and Materials Research Institute, Pennsylvania State University
  • , Kabindra KafleAffiliated withDepartment of Chemical Engineering and Materials Research Institute, Pennsylvania State University
  • , Andrew MooreAffiliated withDepartment of Forest Biomaterials, North Carolina State University
  • , David K. JohnsonAffiliated withNational Renewable Energy Laboratory
  • , Sunkyu ParkAffiliated withDepartment of Forest Biomaterials, North Carolina State University Email author 
  • , Seong H. KimAffiliated withDepartment of Chemical Engineering and Materials Research Institute, Pennsylvania State University Email author 

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Abstract

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.

Keywords

X-ray diffraction Sum frequency generation spectroscopy Infrared spectroscopy Raman spectroscopy Nuclear magnetic resonance Crystallinity index Wood pulp