Rietveld analysis of nanocellulose crystallinity using XRD of different biomass sources

Authors: Jordan, Jacobs; French, Alfred - Al; Easson, Michael

Submitted to: American Chemical Society National Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 5/17/2023
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Powder diffraction is a convenient and widely used tool to study cellulosic nanomaterials. The obtained diffraction patterns can provide insight into the purity and structure of the sample. For example, the observed powder diffraction pattern for cellulose I and cellulose II can be readily distinguished. Often, for cellulosic samples, the question at hand is one of determining the amount of crystalline material present compared to the amount of non-crystalline or amorphous material present. There are several techniques available for crystallinity determination of cellulose and nanocellulose using powder x-ray diffraction. The most predominately used method is the Segal method, and common alternative methods include peak deconvolution and amorphous subtraction. However, these have inherent problems: 1) due to the analysis method the amorphous component tends to be overestimated; 2) the methods are employed incorrectly; 3) each method uses only 2–7 “peaks” in the diffraction pattern for calculation, which may contain over 60 individual reflections. The Rietveld analytical method, which uses the entire diffraction pattern for crystallinity determination, overcomes many of these issues, however this method is not standardized and may be considered to overfit the data, therefore more work is needed. Nanocellulose from wood and cotton sources were compared with a materials analysis using diffraction (MAUD) Rietveld software. For data-fitting, factors included variations in unit cell dimensions, background contributions, crystallite anisotropy and preferred orientation. Specific attention was given to variations in cotton samples arising from differences between nanocellulose source from the cotton ginning process—cotton gin motes and cotton gin trash. These were then compared to patterns obtain from wood sources. This powerful tool allows for the analysis of complex mixtures containing multiple crystalline phases and can be useful for the analysis of composite cellulosic materials.