Chemical modification of cellulose has been of growing interest, owing to the abundance and processing challenges of natural cellulose. To date, etherification and esterification are the most effective strategies to modify physicochemical properties of cellulose and append new functionalities. However, they typically require relatively harsh conditions, thus limiting introduction of new functional groups. An alternative strategy to synthesize novel cellulose derivatives is to append a good leaving group to cellulose backbone, followed by nucleophilic substitution reaction. Though tosylation and bromination of cellulose are frequently used, they have drawbacks such as chemo- and regioselectivity issues, high cost, and difficulty in purification. We have successfully developed a method to chemo- and regioselectively chlorinate cellulose esters using MsCl. Compared to bromination of cellulose typically used, this chlorination method has many advantages, including low cost of reagents and ease of separation. The chlorinated cellulose esters are useful intermediates for appending new functionalities by displacement reactions. We have synthesized a library of cellulose ester derivatives by this chlorination/nucleophilic substitution strategy, including cationic and anionic cellulose ester derivatives. These cellulose ester derivatives possess great potentialiii for various applications, including amorphous solid dispersion, tight junction opening, anionic drug delivery, and gas separation membranes. / MS / Cellulose is one of the most abundant natural materials on earth, making up from 30-40% of the weight of every plant on Earth. However, natural cellulose is hard to process into objects for our use, because it can’t be dissolved in water or other simple solvents, and also can’t be melted (it decomposes before it melts). Chemical modification is a useful method to tailor cellulose properties. Conventional methods to do that (making esters and ethers) are limited in scope by harsh reaction conditions.
This thesis focuses on investigating a novel strategy to modify cellulose esters and prepare novel cellulose ester derivatives for various applications. Compared to other methods, it shows great potential in industrial applications, because of the low cost of reagents, high efficiency and selectivity, and ease of processing the products. By employing this method, we have prepared different cellulose ester derivatives, with a wide range of future applications, such as in membranes for purifying gases, and for effective drug delivery. Besides cellulose esters, the new method is likely to be suitable for modification of many other natural polysaccharides and their derivatives.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/96548 |
| Date | 31 July 2018 |
| Creators | Gao, Chengzhe |
| Contributors | Chemistry, Edgar, Kevin J., Matson, John B., Esker, Alan R., Turner, S. Richard |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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