Engineered Polysaccharides: α-1,3-Glucan Acetates Showing Upper Critical Solution Temperature in Organic Solvents

摘要

Acetates of α-1,3-glucan dissolved in N,N-dimethyl acetamide/LiCl are prepared by converting the polysaccharide with acetyl chloride, acetic acid anhydride/ pyridine, or with acetic acid/N,N′-carbonyl diimidazole. Values of the degree of substitution for the acetyl groups (DS_(Ac)) of up to 2.6 are realized. NMR spectroscopic measurements reveal a preferred conversion of the primary hydroxyl group at position 6 followed by positions 2 and 4. Depending on the DS_(Ac), the samples may be soluble in solvents of different polarity at room temperature or at elevated temperatures showing upper critical solution temperature at DS of about 2.5. This process is found to be reversible.