不同酰基改性淀粉结构及热稳定性研究

Multi-scale Structural Features and Thermal Stabilities of Acylated Starch with Different Acyl Groups

本文用不同链长酸酐对G50玉米淀粉进行化学改性获得酯化淀粉。利用扫描电子显微镜、傅里叶红外光谱、X-射线衍射仪、小角X-射线散射仪及热失重分析仪表征酯化淀粉的表面形貌、分子结构、结晶结构、有序微区结构以及热性能。结果表明,酸酐碳链越长,取代反应程度越低;酯化淀粉颗粒呈碎片状,丁酸酯淀粉(DS=1.38)和己酸酯淀粉(DS=1.37)易聚集成团;酯化淀粉整体呈现无定型态,高取代度乙酸酯淀粉内部有序微区破坏程度最大,取代度相近时,酸酐碳链越长,对应的酯化淀粉存在周期性长程有序结构;相比于原淀粉,酯化淀粉的热稳定性得到增强,且当酸酐添加量相同时,随着酸酐碳链的增加,酯化淀粉的热稳定性增强程度呈下降趋势。以上结果可为完善酯化淀粉应用提供参考。

G50 corn starch was chemically modified using acid anhydrides with different chain lengths to yield starch esters in this study. Scanning electron microscopy （SEM）, Fourier transform infrared spectroscopy （FT-IR）, X-ray diffraction （XRD）, small angle X-ray scattering （SAXS）, and thermogravimetry （TG） techniques were used to characterize the surface morphology, chemical structure, crystalline structure, ordered microdomain structure, and thermal properties of the starch esters. The results indicated that adding anhydride with a longer chain length could lead to a weaker esterification reaction. The starch particles were fragmented into small pieces after esterification reaction, and the butyrate starch （degree of substitution （DS）=1.38） and caproate starch （DS=1.37） tended to aggregate into clusters. All the starch esters presented an amorphous state. The highest degree of damage to the ordered microdomain was found in acetate starch with a high DS. With a similar DS, the starch esters obtained from the anhydride with a long chain length had periodic long-range ordered structures within the starch particles. Compared with the original starch, the starch ester showed enhanced thermal stability. Additionally, when the amount of added acid anhydride was same, the degree of enhancement of thermal stability of the starch ester samples showed a downward trend with increasing chain length of acid anhydride. These results could provide a reference for improvements in the application of starch esterification.