X-ray diffraction is widely used to measure cellulose crystallinity, but accurate measurement of weight-based percentage crystallinity is challenging. A few years ago, we developed a method to measure cellulose crystallinity, accounting for factors such as crystals preferred orientation, incoherent scattering, integral truncation, sample moisture content and other composition deviations from pure cellulose [1]. The method is based on Rietveld modelling of two-dimensional (area-detector) diffraction patterns of cellulose I. Later, we created a novel model, named Cellulose Rietveld Analysis for Fine Structure (CRAFS), which is tailored for analysis of plant cellulose [2]. Since this couple of milestones, we have been employing cellulose crystallinity measurements and CRAFS analysis in a variety of research and development problems. In this talk, we will discuss the principles of two-dimensional Rietveld analysis of plant cellulose. We will highlight the conceptual and operational limits for cellulose crystallinity measurements based on this approach. With this discussion, we expect to contribute to a realistic framework about the underlying assumptions and the achievable accuracy in analysis of X-ray powder patterns, which are inherently less informative than the area-detector patterns. Finally, we will present our vision for advancing the characterization of cellulose crystal-related features, emphasizing intermediate states of order (in-between crystalline and amorphous) and crystal imperfections.<br/><br/>

Cellulose crystallinity determined by two-dimensional Rietveld analysis: Principles, limitations, and prospects

2019 Spring National Meeting

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