Structopendant unsaturated cellulose esters via acylation in homogeneous lithium chloride/N,N‐dimethylacetamide solutions

Abstract

Novel acylation reactions of cellulose were accomplished with a series of unsaturated carboxylic acids or their respective anhydrides including crotonic acid (CRA), methacrylic acid (MAA), vinyl acetic acid (VAA), fumaric acid monoethyl ester (FAME), and cinnamic acid (CINA) in lithium chloride (LiCl)/dimethylacetamide (DMAc) homogeneous solutions. The acylation reactions were conducted at room temperature using dicyclohexylcarbodiimide (DCC) as a condensation agent and 4-dialkyl-aminopyridine (4-[N,N-dimethylamino-] or 4-pyrrolidino-pyridine, DMAP or PP) as a catalyst. A reaction mechanism is proposed based on experimental evidence. The acylated cellulose derivatives obtained from CRA, MAA, or their anhydrides exhibit poor solubility in organic solvents. Side reactions, e.g., the Michael addition, likely occur at the high temperatures required for reaction of these acyl groups. However, acylation of cellulose with VAA, FAME, and CINA is facile with derivatives readily soluble in DMSO. The structures of these derivatized celluloses were characterized with FTIR and 1H-NMR spectroscopy and degrees of substitution were calculated. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 293–305, 1997