Syntheses and Characterizations of Multi-block Copolymers

在甲基丙烯酸酯四氢呋喃的阴离子聚合体系中加入二乙基锌，稳定了增长的烯酸阴离子，降低了聚合速率，提高了活性端的生存能力。采用二乙基锌活性阴离子聚合方法和保护技术，合成了具有3~5个链段的聚甲基丙烯酸铯和聚甲基丙烯酸异丙酯的疏水-亲水嵌段共聚物。用核磁共振和光散射法对嵌段共聚物的一级结构和聚集结构进行了表征。具有5个链段的嵌段共聚物虽然不溶于苯，但一旦溶解在甲醇中，溶剂就会逐渐与苯交换，然后冷冻干燥。所得固体聚合物以106g/mol的胶束形式完全溶于四氢呋喃。透射电子显微镜观察表明，胶束呈圆柱形。当四氢呋喃中的聚合物通过聚苯乙烯凝胶柱时，聚集体被分解成缔合数为5-10的小胶束。用类似的方法合成了具有聚(HEMA)、聚(甲基丙烯酸叔丁酯)和聚(2-全氟丁基)甲基丙烯酸乙酯的ABC型嵌段共聚物。核磁共振数据表明，嵌段共聚物在氯仿和甲醇等选择性溶剂中产生了不同类型的聚集体，这取决于链段的顺序。

Addition of diethylzinc to the anionic polymerization system of methacrylates in THF caused stabilization of the propagating enolate anion to lower the polymerization rate and to enhance the ability of survival of the living end. Using living anionic polymerization method with diethylzinc and the protection technique, hydrophobic-hydrophilic block copolymers of poly (cesium methacrylate) and poly (isopropyl methacrylate) having 3-5 segments were synthesized. The primary structure and aggregate structure of the block copolymers were characterized by NMR and light scattering measurements. Although the block copolymer having 5 segments was insoluble in benzene, it was once dissolved in methanol and the solvent was gradually exchanged with benzene and then freeze dried. The solid polymer obtained was completely soluble in THF as a micelle having 106 g/mol. The cylindrical shape of the micelle was suggested from the TEM observation. When the polymer in THF was passed through the polystirene-gel column, the aggregate was broken down to a small size micelle of 5-10 association number. This suggests that the multi-block copolymer having ca.20 segments forms a unimer micelle.The ABC type block copolymers having poly (HEMA), poly (tert-butyl methacrylate), and poly [(2-perfluorobutyl) ethyl methacry late] were synthesized using a similar method. The NMR data suggested that the block copolymers generated the different types of aggregates in the selective solvents, such as chloroform and methanol, depending upon the sequence of the segments.