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

非技术概述：纤维素是一种来自植物的丰富的可再生聚合物，可以加工成不同厚度的纤维，一直到纳米级。然而，天然纤维素中主要结构组分——纤维素晶体和微原纤维的形态和性质关系尚不清楚。为了更有效地将可持续纳米级纤维素纳入复合材料，包括水过滤膜，有必要提高我们对这些聚合物的结构、形态和性能的基本认识，作为纤维来源和加工方法的功能。这项研究包括实验和理论两部分，从基础科学延伸到水过滤应用。它还将对培养学生从事与可持续材料有关的科学研究方面产生广泛影响。将开展一系列教育活动，让本科生和高中生在学习有关水净化的基本概念的同时，将获得清洁水作为全球可持续性问题进行思考。该项目有可能导致开发新的环境和经济上可持续的水过滤材料，这可能对全球许多人的生活产生积极影响。技术概述：该项目的目标是对纤维素微原纤维（即新生晶体）的结构、形态和性质、它们与纤维来源和分离方法的关系以及这些天然纳米级材料在水净化中的应用有一个基本的了解。本研究利用了最近的发现，即使用tempo介导的氧化和机械分解的化学处理可以产生带负电荷的纤维素微原纤维。氧化微原纤维中带电羧酸基团的大表面密度不仅提高了微原纤维在水中的分散能力，可以进行详细的结构分析，而且为其他自由基的化学接枝提供了机会。在这项研究中，纤维素微原纤维的结构信息将通过联合同步加速器小角度x射线散射（SAXS）、高分辨率透射电子显微镜（TEM）和分子模拟技术来确定。此外，表面修饰的纤维素微原纤维（具有正电荷和负电荷能力）将被探索作为去除水中污染物（如病毒和有毒金属离子）的高吸水性材料，其性能将与结构和功能相关。

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.