An efficient, one-pot acylation of cellulose under homogeneous reaction conditions

Cellulose samples from cotton linters, sisal, and sugar cane bagasse have b een successively acylated (acetate, propionate, butyrate, and acetate/butyr ate) under homogeneous reaction conditions, in LiCl/N,N-dimethyl-acetamide (DMAC), by the following procedure: (i) cellulose and LiCl are heated under reduced pressure, at 110 degrees C (ii) cellulose is dissolved in LiCl/DMA C by heating at 155 degrees C, followed by cooling to 40 degrees C (iii) th e solubilized polymer is acylated at 60 degrees C for 18 h. Attractive feat ures of this one-pot procedure include: easy control and high reproducibili ty of the degree of substitution; elimination of base catalyst; negligible degradation of the natural polymer; and recovery/recycling of high purity D MAC and acid anhydride. Reaction conditions employed for the present cellul oses are different from those previously used for Avicel PH 101 microcrysta lline cellulose because their fibrous nature, higher indices of crystallini ty and higher molecular weights retard their dissolution and decrease their rates of acylation by acid anhydrides.