Cellulose acetate grafting procedure

The selective oxidation of cellulose to dialdehyde by sodium periodate is well known. It has been postulated by Criegee (74) and by Waters (73) that this reaction proceeds by a free radical mechanism. Toda (76) and Morimoto, Okada, Okada, and Nakagawa (77) have concluded that sodium periodate oxidation should initiate graft polymerization. They succeeded in grafting methyl methacrylate and acrylonitrile onto cellulose substrates, such as rayon and paper. A similar procedure is recommended in a patent of Chemische Werke Huels (78) to graft vinyl monomers onto cotton, polyethylene oxide, copolymers of vinyl chloride-vinyl acetate, and others. 

In order to make the separation of unreacted cellulose from the apparent graft easier it was acetylated under nondegradative conditions in acetic anhydride-pyridine mixtures. The apparent graft copolymer was first soaked in methanol, methanol was replaced by water and then acetylated with a 1 2 acetic anhydride-pyridine mixture for 36 hr at 100 °C. After the reaction, the product was precipitated with n-hexane. The precipitate was redissolved in chloroform-methanol and reprecipitated with methanol. The reprecipitation was repeated and finally a purified acetylated product was obtained. When pure cellulose was used for the acetylation it was confirmed that by this procedure cellulose is converted almost totally (98.5 to 99,6%) to triacetate. 

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