Details

Autor(en) / Beteiligte

• Hampe, R.
• Heinze, T.

Titel

Studies About the Solvent-Dependent Substitution Pattern of Starch Acetates

Ist Teil von

• Macromolecular materials and engineering, 2014-10, Vol.299 (10), p.1188-1196

Ort / Verlag

Weinheim: Blackwell Publishing Ltd

Erscheinungsjahr

2014

Quelle

Wiley-Blackwell Journals

Beschreibungen/Notizen

• Starch acetates bearing the ester moiety predominantly at position 2 of the anhydroglucose unit (AGU) could be synthesized by converting starch with acetic anhydride and imidazole in dimethyl sulfoxide (DMSO). Degraded starch (weight average molar mass, M‾w < 16 460 g mol−1) is additionally acetylated at position 6 exceeding a total degree of substitution (DS) of 0.5. Increasing the concentration of starch up to 50 wt% leads to higher partial DS at position 6 under comparable reaction conditions. Using molten imidazole as solvent, an initial regioselective 6‐O‐acylation is achieved. At higher DS values (>0.3), a random distribution of the substituents appears. The substitution pattern can be revealed precisely by means of 13C and 1H NMR spectroscopy after perpropionylation. Hydrolytic stability of a selected 2‐O‐acetyl starch in aqueous solution is evaluated by time‐dependent capillary viscosimetry. The substitution pattern of starch acetates prepared via acetic imidazolides can be adjusted by variation of solvent. Acetyl starches prepared in dimethyl sulfoxide (DMSO) show a preferred 2‐O‐substitution whereas the reaction carried out in molten imidazole leads to 6‐O‐substitution initially. Influences of starch concentration and type of starch on the selectivity are described.