Synthesis And Characterization Of Carboxymethylation Of Starch And Hydroxypropyl Starch In Ionic Liquid

In this paper, an ionic liquid, namely1-butyl-3-methylimidazolium chloride (BMIMCl),was employed as a reaction medium for homogenous carboxymethylation andhydroxypropylation of corn starch. The influence of reaction conditions, such as the amountof catalyst, the mole ratio of reagent, the reaction time, the reaction temperature，the differenttypes of starch and the number of the reuse of ionic liquid on the degree substitution of starchderivatives were investigated. The results showed that the optimal of reaction condition were:n(NaOH):n(SMCA):n(AGU)=1.2:1.0:1.0,reaction time3h,temperature90℃, the degreesubstitution of the carboxymethyl starch was0.76;10%NaOH, propylene oxide dosage3ml,reaction time90min, reaction temperature90℃, the molar substitution degree ofhydroxypropyl startch was1.36. The results also indicated that the ionic liquid could berecycled and reused employing as a new environmemtally solvent.Furthermore, the Fourier transform infrared (FT-IR) spectroscopy,13C NMRspectroscopy, scanning electron microscopy (SEM), X-ray powder diffraction (XRD), andthermal analysis (TGA) techniques were employed to characterize the starch derivatives. Inaddition, physical and chemical properties of the starch derivatives such as clarity,freeze-thaw stability, water absorption and expansion and viscosity were measured. TheFT-IR results of native starch and precipitated starch showed that BMIMCl was a promisingdirect and nonderivitizing solvent for starch. Results from FT-IR and13C NMR spectraindicated that the hydroxyl groups of starches were substituted by carboxymethyl groups.FT-IR and Iodoform reaction results also showed the hydroxyl groups of starches weresubstituted by hydroxypropyl groups. SEM and XRD studies showed that the morphology andcrystallinity of starch was disrupted largely after etherification reaction. It was found that thecarboxymethyl and hydroxypropyl starch were thermally stable than the native starch.Compared with the native starch, the starch derivatives possessed better clarity, freeze-thawstability, water absorption and expansion and viscosity.