Although measurements of crystallinity index (CI) have a long history, it has been found that CI varies significantly depending on the choice of measurement method. In this study, four different techniques incorporating X-ray diffraction and solid-state 13C nuclear magnetic resonance (NMR) were compared using eight different cellulose preparations. We found that the simplest method, which is also the most widely used, and which involves measurement of just two heights in the X-ray diffractogram, produced significantly higher crystallinity values than did the other methods. Data in the literature for the cellulose preparation used (Avicel PH-101) support this observation. We believe that the alternative X-ray diffraction (XRD) and NMR methods presented here, which consider the contributions from amorphous and crystalline cellulose to the entire XRD and NMR spectra, provide a more accurate measure of the crystallinity of cellulose. Although celluloses having a high amorphous content are usually more easily digested by enzymes, it is unclear, based on studies published in the literature, whether CI actually provides a clear indication of the digestibility of a cellulose sample. Cellulose accessibility should be affected by crystallinity, but is also likely to be affected by several other parameters, such as lignin/hemicellulose contents and distribution, porosity, and particle size. Given the methodological dependency of cellulose CI values and the complex nature of cellulase interactions with amorphous and crystalline celluloses, we caution against trying to correlate relatively small changes in CI with changes in cellulose digestibility. In addition, the prediction of cellulase performance based on low levels of cellulose conversion may not include sufficient digestion of the crystalline component to be meaningful.

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Cellulose crystallinity index: measurement techniques and their impact on interpreting cellulase performance

Crystalline structure analysis of cellulose treated with sodium hydroxide and carbon dioxide by means of X-ray diffraction and FTIR spectroscopy.

Effects of short-time vibratory ball milling on the shape of FT-IR spectra of wood and cellulose

With the arising of global climate change and resource shortage, in recent years, increased attention has been paid to environmentally friendly materials. Trees are sustainable and renewable materials, which give us shelter and oxygen and remove carbon dioxide from the atmosphere. Trees are a primary resource that human society depends upon every day, for example, homes, heating, furniture, and aircraft. Wood from trees gives us paper, cardboard, and medical supplies, thus impacting our homes, school, work, and play. All of the above-mentioned applications have been well developed over the past thousands of years. However, trees and wood have much more to offer us as advanced materials, impacting emerging high-tech fields, such as bioengineering, flexible electronics, and clean energy. Wood naturally has a hierarchical structure, composed of well-oriented microfibers and tracheids for water, ion, and oxygen transportation during metabolism. At higher magnification, the walls of fiber cells have an interes...

https://www.fpl.fs.fed.us/documnts/pdf2016/fpl_2016_zhu001.pdf

Wood-Derived Materials for Green Electronics, Biological Devices, and Energy Applications.

FTIR analysis of cellulose treated with sodium hydroxide and carbon dioxide.

Characterization of the crystalline structure of cellulose using static and dynamic FT-IR spectroscopy.

Interactions between wood polymers studied by dynamic FT-IR spectroscopy

In order to define the role of lignin for stress transfer in the fiber wall, its orientation and mechanical interaction with other cell-wall components were investigated. Polarized infrared spectra of oriented thermomechanical pulp fiber sheets were used to determine the molecular orientation, and dynamic infrared spectroscopy was used to study the rheology of lignin in the cell wall. The results indicate that there is a preferred orientation of the phenyl-propane units of lignin along the fiber axis in spruce tracheids. This implies there is an ordered structure of lignin in the secondary wall of tracheids analogous to that of the cell-wall polysaccharides. The dynamic IR-spectra also indicated that lignin exhibits a much more viscoelastic behavior than do the carbohydrates, a knowledge of importance in the interpretation of transverse fiber properties.

Margaretha Åkerholm

Papers

Characterization of the crystalline structure of cellulose using static and dynamic FT-IR spectroscopy.

Interactions between wood polymers studied by dynamic FT-IR spectroscopy

The Oriented Structure of Lignin and its Viscoelastic Properties Studied by Static and Dynamic FT-IR Spectroscopy

Effect of fiber orientation in dynamic FTIR study on native cellulose

Load distribution in native cellulose.