Homogeneous synthesis and characterization of starch acetates in ionic liquid without catalysts

Homogeneous modification of corn starch with acetic anhydride was performed in ionic liquids 1-butyl-3-methylimidazolium chloride (BMIMCl) without catalysts. The results indicated that the pretreatment of starch, which starch was dissolved in BMIMCl at 1058C for 2 h before reaction, provided feasible reaction environment for starch functionalization. Optimum modification conditions for maximum degree of substitute (DS 2.11) were shown as following: acetic anhydride/anhydroglucose units (AGU) molar ratio 5:1, reaction temperature 1058C and reaction time 2 h. The pretence of acetyl groups in starch products was confirmed by FTIR and H NMR spectroscopy. SEM and XRD data showed that the crystalline structure of native starch was disrupted and new structure was formed during the dissolution and modification processes. The higher DS due to acetylation had a beneficial effect on the thermal stability of samples. Received: May 18, 2011 Revised: July 3, 2011 Accepted: July 4, 2011