研究了离子液体1-烯丙基-3-甲基咪唑氯盐AMIMCl及AMIMCl/水二元共混体系对蜡质玉米淀粉的颗粒形态、热行为及结晶结构等相关特性的影响。采用热台偏光显微镜在线监控了室温及升温过程中,淀粉颗粒在离子液体/水二元共混体系中的形态演变,同时采用差示扫描量热仪和X射线衍射仪对离子液体处理后的淀粉样品的热行为和结晶性质进行表征。研究发现:AMIMCl/水共混溶液体系对淀粉的颗粒形态及结晶结构影响显著,且与溶液中AMIMCl的含量密切相关。当共混溶液中AMIMCl/水的比例低于50/50时,淀粉偏光十字消失的温度区间随着体系中AMIMCl含量的增加而升高,与DSC吸热峰向高温区迁移的现象相吻合,糊化温度可提高至84℃,此时淀粉分子内和分子间的主要作用键有所增强;当AMIMCl/水比例大于50%时,糊化温度和焓值可减少至62℃和12.45 J/g,此时淀粉链间结构被破坏,淀粉分子的稳定性降低,糊化和溶解同时发生。在纯离子液体中,由于没有水分子的参与,只有溶解现象发生,且随着贮存时间的延长,溶解现象愈发明显。
In this study, the effect of the ionic liquid 1-allyl-3-methylimidazolium chloride(AMIMCl) and a AMIMCI/water binary blend system on the morphologies, thermal properties, crystalline structures, and related properties of waxy corn starch granules were systematically studied. A hot-stage microscope was used to monitor the morphological changes of starch granules in the ionic liquid/water binary blend system at room temperature and during the heating process. The thermal behavior and crystallinity of the ionic liquid-treated starch sample were characterized by differential scanning calorimetry(DSC) and X-ray diffraction. The results showed that the AMIMCl/water blend system had a significant impact on the morphology and crystalline structure of starch granules; these properties were closely related to the AMIMCI content. When the AMIMCl content in the solution was less than 50%, the temperature range for the disappearance of the cross-polarization of starch increased with increasing AMIMCI content, consistent with the observation that the endothermic peak in DSC was shifted to the high-temperature side. When the gelatinization temperature was increased to 84 ℃, the strengths of the intramolecular and intermolecular forces of starch increased. When the AMIMCl content in solution was more than 50%, the gelatinization temperature and enthalpy decreased to 62 ℃and 12.45 J/g, respectively. At the same time, the interchain structures of starch were destroyed, the stability of starch molecules decreased, and starch dissolution and gelatinization occurred simultaneously. In pure AMIMCl, because of the absence of water, only starch dissolution occurred and became more apparent with increasing storage time.