Synthesis, control of substitution pattern and phase transitions of 2,3-di-O-methylcellulose

An improved heterogeneous procedure has been found for the regioselective i ntroduction of trityl and 4-methoxytrityl groups at the primary positions o f cellulose. The 6-O-tritylcelluloses produced were completely methylated b y MeI-NaOH in Me2SO solution. The trityl groups were then completely remove d to afford 2,3-di-O-methylcellulose without significant degradation of the polymer. H-1 and C-13 NMR spectroscopy and degradation analysis showed les s than 5% deviation from the regular substitution pattern. Under optimum re action conditions, almost perfectly regular cellulose derivatives could be obtained. Small changes in the substitution pattern had a strong effect on the phase transitions of the O-methylcelluloses in water. It was shown by D SC for the first time that perfect 2,3-di-O-methylcellulose does not underg o phase separation at elevated temperatures. (C) 2000 Elsevier Science Ltd. All rights reserved.