Synthesis of Amphiphilic Triblock Copolymers and their Application on the Preparation of Porous Materials

本篇論文的工作係將乙二醇甲基醚末端以酯鍵或醯胺鍵結方式與2-溴-2-甲基丙醯溴反應做為巨起始物，在無水無氧條件下，連續以丙烯酸甲酯與苯乙烯為單體，利用原子轉移自由基聚合法合成出ABC型三區塊共聚物--聚乙二醇甲基醚-聚丙烯酸甲酯-聚苯乙烯，其分子量分布的PDI值介於1.21至1.33之間。以酯鍵鍵結的三區塊共聚物為模板，改變溶劑組成(純水或共溶劑四氫呋喃、乙醇)、pH值，可以合成出具有六方堆接結構的規則性孔洞二氧化矽材料。 由於醯胺鍵對酸鹼穩定性較高，遂將以醯胺為鍵結的三區塊聚合物中的丙烯酸甲酯區塊水解成對應酸根，使其增加共聚物在水中的溶解度。水解後的三區塊共聚物可溶於pH值大於3的水溶液中，但得到的二氧化矽材料不呈現中孔洞，且其表面積小，孔洞體積亦少。若在pH值為5~7之間之條件下，加入鈷離子做為添加物，可合成出具有泡沫狀(foam-like)的中孔洞矽材，鍛燒後的樣品具有高表面積(350-500m2g-1)、高孔體積(1.0-1.2cm3g-1)，以及孔洞大小一致(約20nm)的優點。鈷含量隨著pH值的增加而增加。經過FTIR、TPR、Powder XRD證明鈷是存在於二氧化矽骨架中，而非以奈米粒子形式存在。此含鈷金屬材料能催化芳香類化合物的烷基化反應。By using atom transfer radical polymerization (ATRP), triblock copolymers poly(ethylene glycol)-b-(methacrylate)-b-styrene, EO45MAmSTn have been prepared and their PDI values (Mw/Mn) of these copolymers are in the range of 1.21 ~ 1.33. The obtained copolymers are used as templates for the preparation of mesoporous silica materials. By controlling the length of polystyrene, the ratio of co-solvents and the pH value, ordered mesoporous silicas can be obtained. Hydrolysis of the methacrylate on the triblock copolymers provided the corresponding carboxylic acid (-COOH) material (EO45MAOHmSTn). Due to the highly polar nature of –COOH, the morphology of the obtained silicas is totally different from the non-hydrolyzed copolymers. Furthermore, we have learned that the addition of cobalt ions play an important role for the synthesis of mesoporous silicas. Without cobalt ions, the micelles are not stable after the pre-hydrolysis TEOS added, which leads to the formation of nonporous silicas. On the other hand, foam-like mesoporous silicas were constructed in the presence of the cobalt ions under the pH ranging from 5 to 7. After calcination, the loading of cobalt was found to be in the range of 1% ~ 11%; the cobalt content increases with the increasing pH value. These foam-like materials have high BET surface area (350-500m2/g), large pore volume (1.0-1.2cm3/g) and uniform pore size (~20nm). The cobalt containing materials can be used as heterogeneous acid catalyst and show good catalytic activity on Friedel-Craft alkylation