MODIFICATION OF NATURAL POLYMERS BY THERMO-MECHANICAL PROCESSING
Location: Plant Polymer Research
Title: SOLVENT FREE PROCESS TO ESTERIFY POLYSACCHARIDES
Submitted to: Biomacromolecules
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 21, 2005
Publication Date: July 1, 2005
Citation: Biswas, A., Shogren, R.L., Willett, J.L. Solvent free process to esterify polysaccharides. Biomacromolecules. 2005.
Interpretive Summary: Starch and cellulose, earth's most abundant biopolymers, are of tremendous economic importance. Over 90% of cotton and 50% of wood are made of cellulose. Wood and cotton are the major resources for all cellulose products such as paper, textiles, construction materials, cardboard, as well as such cellulose derivatives as cellophane, rayon, and cellulose acetate. Similarly, acetylated starches have been known for over 100 years and have found applications. However, cellulose acetates are industrially more important and it is estimated that annually 1.5 billion pounds of cellulose acetates are manufactured globally. Cellulose acetate is widely used in textiles because of its low cost, toughness, gloss, high transparency, natural feel, and other favorable aesthetic properties. Cellulose acetate fibers in cigarette filters are designed to absorb vapors and accumulate particle smoke components. Cellulose acetate is also used as a carrier for photographic negatives, motion picture film (celluloid), microfilm, microfiche and audio tape. We would like to report a simple solvent-less rapid method to acetylate cellulose, starch and other polysaccharides. We have found that acetic anhydride in presence of catalytic amount of iodine is an excellent acylating reagent for both starch and cellulose. It is believed that iodine activates the carbonyl group of acetic anhydride, which renders it more reactive. Thus, iodine-activated acetic anhydride is strong enough acylating agent to react with polysaccharides directly. This reagent works only in the absence of a solvent. Furthermore, when cellulose was heated with acetic acid and iodine, there was no reaction and cellulose remained unreacted. This solvent-free method that we discovered would help the starch/cellulose acetate manufacturers to prepare strch or cellulose acetate in an environment friendly way. This method eliminates the use of solvents and acids.
A novel method for the preparation of acetates of polysaccharides is described herein, involving the concurrent use of iodine and acetic anhydride. The method is simple, rapid, efficient, and solvent-less. With this method, cellulose and starch acetates have been synthesized.