The issue of crystallinity in cellulose goes back for many years. Our multi-institution studies used a combination of methods to investigate changes in cotton cellulose as it was ball milled for 15, 45 and 120 minutes. Techniques included optical and FE-SEM micrographs that showed changes in particle size. Molecular weight and carbonyl group analyses by gel permeation chromatography (GPC) confirmed chemical changes. Specific surface area increased, although pore size dropped before increasing. Thermogravimetric analysis results indicated progressive increases in initial moisture content and some loss in stability. Fourier Transform IR and Raman spectroscopy also indicated progressive changes; some proposed indicators of crystallinity for FTIR were not in good agreement with our results. Laboratory and synchrotron X-ray results with the Rietveld method showed similar decreases in effective crystallite size despite some disagreement on the amount of crystalline cellulose in the control sample. <sup>13</sup>C ssNMR studies informed by Dynamic Nuclear Polarization) natural abundance 2-D NMR studies did not rely on the modeled paracrystalline cellulose and inaccessible crystallite surfaces used by the conventional analysis. Both the Sum Frequency Generation analyses, which showed profound changes in the SFG signal, and the NMR analyses depend on assumed domain sizes that are areas for continued discussion.

Changes in cotton cellulose caused by ball milling - a thirteen technique exploration

2019 Spring National Meeting

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