SusChEM: Structure and Property Study of Nascent Cellulose Nanocrystals and Their Use in Water Purification

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NON-TECHNICAL SUMMARY: Cellulose is an abundant renewable polymer from plants and can be processed into fibers of different thicknesses all the way down to the nanoscale. However, the morphology and property relationships of the primary structural components -- cellulose crystals and microfibrils -- in the natural cellulose are still not clear. In order to more effectively incorporate sustainable nanoscaled cellulose into composite materials, including water filtration membranes, it is necessary to improve our fundamental understanding of the structure, morphology and properties of these polymers as functions of fiber source and processing methods. This research includes both an experimental and a theoretical component and extends from fundamental science to water-filtration applications. It will also have a broad impact in training of students in scientific research relevant to sustainable materials. A range of educational activities will be developed to engage undergraduate and high school students in thinking about access to clean water as an issue of global sustainability while learning about the fundamental concepts on water purification. This project has the potential to lead to the development of new environmentally and economically sustainable materials for water filtration that could positively impact the lives of many people around the globe. TECHNICAL SUMMARY: The goal of this project is to develop a fundamental understanding of the structure, morphology and properties of cellulose microfibrils (i.e., nascent crystals), their relationships with fiber source and isolation method, and the applications of these naturally occurring nanoscale materials for water purification. This research takes advantage of the recent findings that the chemical treatment using TEMPO-mediated oxidation followed by mechanical disintegration can produce negatively charged cellulose microfibrils. The large surface density of charged carboxylate groups in oxidized microfibrils not only improves the dispersion capability in water, allowing detailed structural analysis, but also provides opportunities for chemical grafting of other radicals. In this research, structural information on cellulose microfibrils will be determined by combined synchrotron small-angle X-ray scattering (SAXS), high-resolution transmission electron microscopy (TEM) and molecular simulation techniques. In addition, surface-modified cellulose microfibrils (with both positive and negative charge capability) will be explored as superabsorbent materials to remove contaminants (e.g. viruses and toxic metal ions) in water, and their performance will be correlated with structure and functionality.