Preparation And Characterization Of Long-chain Fatty Acid Esters Of Starch And Cationic Starch In BMIMCL

Ionic liquids have been used in a wide range for their unique characters. Especially, the 1-butyl-3-methylimidazolium chloride (BMIMCl) has been found to be nonderivatizing solvents for polysaccharides such as starch compared to the traditional organic solvents.In this work, long-chain fatty acid esters of starch,the high-DS cationic starch and low-DS cationic starch were synthesized in the ionic liquid BMIMCl. The influence of reaction time, reaction temperature, the amount of catalyst and molar ratio of reagent on the degree of substitution (DS) of products was investigated. The highest DS value of starch laurate obtained was 0.365, in which a reaction temperature of 120℃, a molar ratio of AGU: methyl ester: pyridine of 1:4:0.5 and a reaction time of 2 h were employed. For the satrch stearate, the highest DS value of 0.276 could be achieved in the conditions of reaction temperature of 110℃, a molar ratio of AGU: methyl ester: pyridine of 1:4:2 and a reaction time of 2 h. The highest DS value of the high-DS cationic starch obtained was about 0.99, in which a reaction temperature of 80℃, a molar ratio of AGU: GTAC: NaOH of 1:3:0.135 and a reaction time of 2 h were employed. For the low-DS cationic starch, the DS of 0.0331 was obtained in the conditions of reaction temperature of 80℃, a molar ratio of AGU: CTAC: NaOH of 1:1:0.5 and a reaction time of 2 h. Moreover, the ionic liquid could be recycled and reused.Furthermore, the structure of starch derivatives was characterized by means of Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), X-ray powder diffraction (XRD), thermal analysis and 1H NMR spectroscopy. The SEM and XRD results showed that the ordered crystalline structure of native starch was largely destroyed during the dissolution and functionalization of starch in the ionic liquid BMIMCl. In addition, the properties of the starch derivatives such as transparency, contra-retrogradation, flocculation characteristics were measured. The results showed the starch esters had a good transparency and contra-retrogradation, the high-DS cationic starch was an effective flocculating agent.