苯乙烯-乙烯吡啶團聯共聚物在膽酸中的自組裝形態

Abstract

雙親性團聯式共聚物在選擇性溶劑中，其親溶劑鏈段會與溶劑接觸，非親溶劑鏈段因不相容於溶劑當中，而被親溶劑鏈段包圍以避免與溶劑接觸，因此可以自組裝形成微米或奈米等級尺寸結構。常見的結構包含球狀微胞、柱狀微胞、球狀液胞等等，形成這些微結構的條件與機制已被廣泛的研究。 不同於以往的液態溶液系統，本研究發現團聯式共聚物 PS-b-P4VP 在高溫熔融態的脫氧膽酸(Deoxycholic acid)中能形成一系列的自組裝結構，當溫度下降至室溫後，其微結構仍可完整保留，而形成特殊的固態自組裝系統。我們利用穿透式電子顯微鏡觀察在適當的退火溫度與時間下，可藉由改變團聯式共聚物分子量，而製備出球狀微胞、柱狀微胞、液胞等不同的微結構。另外，調整退火時間與溫 度，其微結構也會隨之改變，我們將在論文中提出微結構形成的機制。 由於微結構可保留在固態脫氧膽酸中，所以我們嘗試將脫氧膽酸以溶劑去除，並觀察到在脫氧膽酸移除後，團聯式共聚物所形成的微結構可被完整萃取出來。這些萃取出來的微結構，尤其是液胞結構，有機會進一步應用於藥物釋放甚至其他領域。

Amphiphilic block copolymers in selective solvents self-assemble into micro/nano-scaled structures, such as spherical micelles, cylindrical micelles and vesicles, in which solvent-philic blocks tend to contact with solvents and shield solvent-phobic blocks from the solvents. The formation conditions and mechanisms of such structures have been widely studied. Different from the conventional micellization in liquid systems, ,in this study we found that block copolymer poly(styrene-block-4-vinylpyridine) (PS-b-P4VP) can self-assemble in melted deoxycholic acid (DCA) at high temperature and more interestingly, the structures can be retained in “solid state” after cooled down to room temperature. Transmission electron microscopy (TEM) was used to probe the structure and we found that different self-assembled structures, including spherical micelles, cylindrical micelles and vesicles can be obtained by varying the length of block copolymers and the morphologies depend on annealing temperature and annealing time. We will discuss the mechanisms of the micellization in this thesis. Since these nano-structures can be retained in solid state, we tried to extract the nano-structures by removing deoxycholic acid using appropriate solvents. These extracted structures, especially the vesicles, are potential for applications, such as drug delivery.