A reactive extrusion process for the production of substituted polysaccharides, in particular, cellulose acetate, starch acetate, carboxymethyl cellulose, and carboxymethyl starch. The present application claims the benefit of PCT/ US20111059785 filed on Nov. 8, 2011, which claimed the benefit of U.S. provisional application 611411,521, filed on Nov. 9, 2010, U.S. provisional application 611411,992, filed on Nov. 10, 2010, and U.S. provisional application 611472, 748, filed on Apr. 7, 2011, each of which is which is incorporated herein by reference in its entirety. The production of substituted polysaccharides such as starch and cellulose acetates and carboxymethylated starches and celluloses have typically been produced using batch reactor...