Surprising Insensitivity of Homogeneous Acetylation of Cellulose Dissolved in Triethyl(n‐octyl)ammonium Chloride/Molecular Solvent on the Solvent Polarity

Abstract

The homogeneous acetylation of microcrystalline cellulose (MCC) by acetyl chloride and acetic anhydride in triethyl(n-octyl)ammonium chloride (N 2228 Cl)/ molecular solvents (MSs) is investigated. The reaction with both acylating agents shows the expected increase of the degree of substitution (DS) on reaction temperature and time. Under comparable reaction conditions, however, DS is surprisingly little dependent on the MS employed, although the MSs differ in empirical polarity by 7 kcal mol −1 as calculated by use of solvatochromic probes. The empirical polarities of (MCC + N 2228 Cl + MS) differ only by 0.8 kcal mol −1 . The formation a polar electrolyte sheath around cellulose chains presumably contributes to this "leveling-off" of the dependence DS on the polarity of the parent MS employed. N 2228 Cl recovery and recycling is feasible. 1800032 (2 of 8) www.advancedsciencenews.com www.mme-journal.de

Solvent-Free Acetylation of Cellulose by 1-Ethyl-3-methylimidazolium Acetate-Catalyzed Transesterification

“…Although this process has been used to produce cellulose acetate for more than 100 years, it suffers from corrosion due to the presence of these applied acids and also from depolymerization of cellulose chains by acid-catalyzed hydrolysis. Over the years, a numbers of processes for cellulose acetate synthesis have been developed. − Chemically, these cellulose acetylation processes include the reaction of −OH groups from cellulose with anhydride, , acetyl chloride, ketene, acetylamine, acetic acid associated with dicyclohexylcarbodiimide, carbonyldiimidazole, oxalic acid chloride, and tosyl chloride as activators, − and vinyl esters by transesterification (shown in Figure ). Among these approaches, acetylation of cellulose with acetic anhydride has been the center of research and industry over the years because of reactant availability, high reactivity, and controllability, although the process inherently leads to extensive depolymerization of cellulose and is highly corrosive.…”

The Effect of Additives on the Viscosity and Dissolution of Cellulose in Tetrabutylphosphonium Hydroxide

“…Stirring of the solution to improvet he homogeneous environment was still difficult, limiting further processing and application. The utilization of solvents can enable adjustment of the viscosity, by using high-viscoset ol ow-viscose cellulose solutions [15] (e.g., by acetylation [16] ).…”