- 學位論文
以線性聚苯乙烯與星狀聚苯乙烯為成孔劑改變聚醯亞胺之孔隙性及其材料製備與性質探討
Preparation and characterization of porous polyimide with linear-polystyrenes and star-polystyrenes as pore agents
摘要
本研究中，我們首先利用ATRP反應成功地聚合出線性及星狀聚苯乙烯， GPC數據顯示這些高分子的分子量分佈均小於1.2。然後，再將所聚合出的聚苯乙烯當作成孔劑，添加至BTDA-MDA聚醯亞胺中，利用熱裂解法除去聚苯乙烯而形成多孔性聚醯亞胺。 我們藉由SEM去觀察膜材內部結構，並從結果觀察到，膜材內部產生了許多小孔隙。利用AFM去量測膜材的表面結構，可得到隨著成孔劑量增加，其粗糙度有小幅度的提升。 我們可從TGA的數據得知道BTDA-MDA聚醯亞胺之5%熱裂解溫度，亦可從圖發現我們所加入的成孔劑到底有沒有完全被移除。在DSC的數據上可得知道，隨著孔隙的增加，其玻璃轉移溫度也隨之下降。由TMA的量測圖，可計算出BTDA-MDA聚醯亞胺之熱膨脹係數，並得知道BTDA-MDA聚醯亞胺薄膜內之孔隙並不會去影響到其熱膨脹係數。 經由介電常數量測儀，去量測出膜材的電容值，再帶入公式去計算介電常數，從介電常數值可以發現到，隨著我們成孔劑的含量增加，其介電常數下降的越多，使用不同分子量大小之成孔劑，介電常數也會不同。就添加相同重量百分比而言，成孔劑的分子量越大，介電常數下降的也越多。
並列摘要
Both linear and star-like polystyrenes were successfully synthesized by atom transfer radical polymerization (ATRP) method. GPC data indicated these polymers have very narrow molecular weight distribution with a polydispersity less than 1.2. Then these polymers were added into the polyamic acid solution of BTDA-MDA as porogen. After the solution had been spin-coated on top of a glass substrate, the polystyrene in the as-prepared composite films were thermally decomposed to yield porous polyimide. The porous structure of polyimide was observed by SEM and the surface roughness of polyimide was examined by AFM. The results showed that roughness increased with increasing polystyrene content. The thermal decomposition temperature of polyimide was determined by TGA. The TGA thermograms also confirmed that all porogens were completely removed during preparation process. The glass transition temperatures of polyimide were examined by DSC. The results showed that the glass transition temperature of polyimide decreased as the porosity increased. The coefficient of thermal expansion of polyimide was calculated from the TMA curves. The results showed that the porosity had little effect on the coefficient of thermal expansion of polyimide. The dielectric constant of polyimide was calculated from the capacitance data. The results showed that the dielectric constant decreased with increasing content of polystyrene. The molecular weight of polystyrene also influenced the dielectric constant. The dielectric constant decreased while the molecular weight of polystyrene increased.