Synthesis, control of substitution pattern and phase transitions of 2,3-di-O-methylcellulose.
An improved heterogeneous procedure has been found for the regioselective introduction of trityl and 4-methoxytrityl groups at the primary positions of cellulose. The 6-O-tritylcelluloses produced were completely methylated by MeI-NaOH in Me2SO solution. The trityl groups were then completely removed to afford 2,3-di-O-methylcellulose without significant degradation of the polymer. 1H and 13C NMR spectroscopy and degradation analysis showed less than 5% deviation from the regular substitution pattern. Under optimum reaction 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 DSC for the first time that perfect 2,3-di-O-methylcellulose does not undergo phase separation at elevated temperatures.
Polymer-Institut der Universität Karlsruhe (TH), Hertzstrasse 16, D- 76187 Karlsruhe, Germany.
H
H
Kern
S
S
Choi
G
G
Wenz
J
J
Heinrich
L
L
Ehrhardt
P
P
Mischnick
P
P
Garidel
A
A
Blume
D009682:Magnetic Resonance Spectroscopy; D008747:Methylcellulose / Q000031:analogs & derivatives / Q000138:chemical synthesis / Q000737:chemistry; D015394:Molecular Structure; D044367:Phase Transition; D013237:Stereoisomerism; D013379:Substrate Specificity; D013696:Temperature
D008747:Methylcellulose