离子液体介质中无催化剂法制备硬脂酸玉米淀粉酯的结构与性能

Structure and Properties of Corn Starch Stearate Prepared in Ionic Liquid Medium Without Catalyst

以玉米淀粉(CS)为原料,离子液体氯化1-烯丙基-3-甲基咪唑(AMIMCl)为反应介质,硬脂酸甲酯(MS)为酯化试剂,无催化剂制备硬脂酸玉米淀粉酯(CSS)。利用红外光谱(FTIR)、X射线衍射(XRD)、扫描电镜(SEM)、热重-红外联用(TGA-FTIR)和哈克流变仪对CSS的结构、热特性及流变特性进行分析。通过单因素及正交实验确定制备CSS最佳工艺条件为:温度90℃,时间2.5 h,MS与淀粉(以脱水葡萄糖单元AGU计)摩尔比可根据所需产品的取代度在0.5~3.0范围内选取。结构分析表明,CS已成功与MS发生了酯交换反应,反应按SN2亲核取代机理进行;所制备的CSS失去了CS的结晶与颗粒结构。热特性分析表明,在氮气氛围下CSS所接入的硬脂酸基团能稳定至220℃。流变特性分析表明,CSS糊液为符合幕律定律的假塑性流体,具有触变性。

Corn starch stearate(CSS)was prepared from corn starch(CS)with ionic liquid 1-alkyl-3-methylimidazole chloride(AMIMCl)as the reaction medium and methyl stearate(MS)as esterification reagent without catalyst.The structure,thermal and rheological properties of CSS were analyzed by means of Fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD),scanning electron microscopy(SEM),thermogravi-FTIR(TGA-FTIR)and Haake rheometer.The optimal conditions for CSS preparation were determined by single factor and orthogonal experiment,which is detailed as follows:temperature was 90℃,time 2.5 h,molar ratio of MS to starch(based on anhydroglucose units AGU)could be selected within the range of 0.5~3.0 pursuant to the degree of substitution of required products.The structural analysis showed that the transesterification between CS and MS was successful,and the reaction progressed as per the nucleophilic substitution mechanism of SN2.The prepared CSS lost the crystal structure and particle structure of CS.The thermal characteristics analysis showed that the stearic acid group of CSS was stable to 220℃in nitrogen atmosphere.In addition,rheological analysis showed that CSS paste was a pseudoplastic fluid in accordance with power law.Thus,it had thixotropy.