Syntheses and Characterizations of Multi-block Copolymers

在甲基丙烯酸酯阴离子聚合体系中加入二乙基锌，可稳定增长的烯醇化阴离子，降低聚合速率，提高活性末端的存活能力。采用二乙基锌活性阴离子聚合法和保护技术，合成了3-5段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。通过核磁共振和光散射测试表征了嵌段共聚物的一级结构和聚集态结构。尽管具有5个链段的嵌段共聚物不溶于苯，但将其溶解在甲醇中，并将溶剂逐渐与苯交换，然后冷冻干燥。获得的固体聚合物作为106 g/mol的胶束完全溶于THF。TEM观察表明胶束为圆柱形。当聚合物在THF中通过聚苯乙烯-凝胶柱时，聚集体被分解成5-10缔合数的小尺寸胶束。这表明具有约20个链段的多嵌段共聚物形成单聚物胶束。使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）乙基甲基丙烯酸酯]的ABC型嵌段共聚物。NMR数据表明，嵌段共聚物在选择性溶剂中，如氯仿和甲醇，产生不同类型的聚集体，这取决于链段的序列。

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.