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.