Regioselective chlorination of cellulose esters

Abstract

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.