丙烯酰胺接枝活化淀粉共聚物的结构表征

以机械活化淀粉(St)和丙烯酰胺(AM)为原料，通过反相乳液聚合法制备了机械活化30min和60min的两种淀粉丙烯酰胺接枝共聚物（M30-St-g-PAM、M60-St-g-PAM）。考察了索氏抽提时间对接枝率的影响，采用红外光谱、电镜扫描、X射线衍射、热分析等手段研究了接枝共聚物的结构，并与原玉米淀粉接枝共聚物（St-g-PAM）比较。实验结果显示，丙烯酰胺成功接枝于活化淀粉上；M30-St-g-PAM和M60-St-g-PAM具有网状多孔洞结构，丙烯酰胺与淀粉的接枝共聚反应在淀粉的无定型区和结晶区同时发生，机械活化有效地提高了玉米淀粉的化学反应活性；共聚反应改变了原淀粉的聚集状态，接枝产物基本上为无定型的聚集态结构；热稳定性比St-g-PAM增强。M60-St-g-PAM与M30-St-g-PAM相比接枝反应不均，热稳定性稍有下降。确定了以乙二醇/冰乙酸 (体积比60∶40) 为抽提溶剂完全除去均聚物的抽提时间为8h。

Characterization of graft copolymers of acrylamide on mechanically-activated starch

Graft copolymers of starch are a new kind of functional material. Graft copolymers of acrylamide and starch have been synthesized by inverse emulsion polymerization using mechanically activated maize starch and acrylamide as raw materials. The crude graft copolymer was treated for 8 hours by Soxhlet extraction with a 60∶40 (by vol.) mixture of ethylene glycol and acetic acid, which resulted in complete removal of the homopolymer. Samples produced using starch mechanically activated for 30?min and 60?min are denoted M30-St-g-PAM and M60-St-g-PAM.respectively. The structures of M30-St-g-PAM and M60-St-g-PAM were characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and scanning electronic microscopy (SEM) and compared with a graft copolymer of acrylamide with non pretreated starch (St-g-PAM). The results showed that polyacrylamide (PAM) was successfully grafted onto the mechanically activated starch. M30-St-g-PAM and M60-St-g-PAM were found to have a porous mesh like structure with the graft copolymerization reaction occurring at both crystalline regions and loose amorphous regions of the starch particles. Mechanical activation was found to enhance the reactivity of the starch. Grafting of acrylamide led to a change in the state of the raw starch from semicrystalline to amorphous. The thermal stabilities of M30-St-g-PAM and M60-St-g-PAM were higher than that of St-g-PAM. The graft-copolymerization reaction for M60-St-g-PAM was uneven and the thermal stability was lower than that of M30-St-g-PAM.