CO2/N2可逆单层囊泡-网状结构转变研究

CO2/N2 Switchable Unilamellar Vesicle-Network Structure Transition

摘要:

以聚乙二醇6000与α-溴代异丁酰溴进行酯化反应得到大分子引发剂PEG6000-Br，使用原子转移自由基聚合法合成了对称三嵌段且聚合度相等的聚甲基丙烯酸二甲胺乙酯-聚乙二醇-聚甲基丙烯酸二甲胺乙酯(PDM165-PEG165-PDM165)。利用FT IR和1H NMR对其结构进行了表征。以pH、电导率证明了聚合物溶液性质的CO2/N2循环可逆性，聚合物溶液中通入CO2后，5min内，pH值即从7.74下降至5.47，溶液电导率从0.176 mS/cm迅速上升至0.405 mS/cm；继而向溶液中通入N2，经过30 min后，pH值恢复至初始的7.74，电导率下降至初始值0.177 mS/cm。冷冻透射电镜观察得知聚合物在水中可自组装形成单层囊泡；通入CO2后，叔胺被质子化，囊泡解离形成网状结构，导致溶液黏度从3 mPa•s上升至12 mPa•s；叔胺质子化由1H NMR证明，N原子附近的氢的位移从2.3，2.7，4.1 ppm向低场分别移动至2.8，3.2，4.3 ppm。

Abstract:

A macroinitiator PEG6000-Br, was synthesized by esterification reaction of PEG6000 and α-Bromoisobutyryl bromide. By using ATRP method, a symmetrical triblock polymer with the same degree of polymerization, poly(2-(Dimethylamino)ethyl methacrylate)-PEG-poly(2-(Dimethylamino)ethyl methacrylate) (PDM165-PEG165-PDM165), was synthesized. The structures were characterized by FT IR and 1H NMR. The CO2/N2 switchability was proved by pH and conductivity, after 5 min of bubbling CO2, pH decreased from 7.74 to 5.47 and the conductivity increased from 0.176 mS/cm to 0.405 mS/cm rapidly. Then, after 30 min of bubbling N2, the pH recovered to the initial 7.74 and the conductivity decreased to the initial value of 0.177 mS/cm smoothly. The self-assembled unilamellar vesicles-network transition was observed by cryo-TEM, thus result in enhancement of viscosity increase from 3 mPa•s to 12 mPa•s. The key mechanism of these changes is protonation of tertiary amine groups in PDM blocks and was proved by 1H NMR, the chemical shifts of H near N atom downfield from 2.3, 2.7, 4.1 ppm to 2.8, 3.2, 4.3 ppm, respectively.