利用可逆共价键pH响应性制备聚轮烷

合成了具有可逆酰腙键的2,4-二硝基苯甲醛封端的哑铃型聚乙二醇衍生物. 在60 ℃时将水溶液的pH值调节至酸性, 哑铃型聚合物上的酰腙键发生可逆的“断开”和“生成”. 在这个可逆过程中, 溶液中的α-环糊精逐步与聚乙二醇内含复合. 由于环糊精具有较强疏水作用的内部空腔, 可以与聚乙二醇形成稳定的内含结晶复合物, 在这种超分子作用力下, 哑铃型聚乙二醇衍生物的分子链上会动态地穿入更多的α-环糊精, 最终形成聚轮烷. 综合液体核磁共振、粉末X射线衍射、固体碳-13交叉极化/魔角自旋核磁共振及差示扫描量热分析结果证明, 这种利用可逆共价键pH响应性制备聚轮烷的方法是可行的. 与传统的聚轮烷制备方法不同, 这种利用动态的可逆共价键制备聚轮烷的方法并不需要预先合成准(聚)轮烷.

pH Stimulated Preparation of Polyrotaxane Based on Reversible Covalent Bond in Solution

A novel method to prepare polyrotaxane in solution by α-cyclodextrins and dumbbell-like poly(ethylene glycol) derivative with reversible acylhydrazone bond and big end stopper (2’,4- dinitrophenyl) is described. Stimulated by the pH change to acidic in water at 60 ℃, the reversible acylhydrazone bond could undergo reversible hydrolysis. During this process, α-cyclodextrins can pass through the dynamic reversible bond and thread onto the polymer chain. Because of the relative strong supramolecular interactions between α-cyclodextrins and ethylene glycol units in water, more and more α-cyclodextrins thread onto the polymer chain, leading to the formation of polyrotaxane. Through the combination of 1H NMR, wide-angle X-ray diffraction, 13C CP/MAS NMR and differential scanning calorimetric tests, the formation of polyrotaxane prepared by dynamic method is confirmed. Differing from the traditional routes, the preparation of pseudo(poly)rotaxane is no longer a prerequisite to construct polyrotaxane in this dynamic method. The novel polyrotaxane with reversible covalent bond, which has its inherent dynamic property, has potential use in smart materials and self-healing materials.