不同構形之雙親性PS-b-PMSMA及PS-b-PDMAEMA嵌段共聚物之合成及形態鑑定

Abstract

雙親性嵌段共聚高分子的研究近年來蓬勃發展，不僅發展出不同製備方法，其中許多研究是在探討合成不同親疏水鏈段的共聚高分子，藉由不同極性溶劑加入形成特殊的形態。本論文所探討的共聚高分子其中一鏈段皆為PS，改變另一鏈段的組成，分別為具有可水解交聯基團矽氧烷(-Si-(O(CH3))3)的PMSMA或環境應答型的PDMAEMA，合成線性及雜臂星形 (heteroarm)共聚高分子，並觀察在溶液中的形態。論文分為兩大部分：(1)觀察線性PS-b-PMSMA在PS選擇性溶液與PMSMA選擇性溶液中的形態。(2)觀察線性 PS-b-PDMAEMA與雜臂星形 (heteroarm) PSn-PDMAEMAn共聚物在PDMAEMA選擇溶液及及不同pH值和溫度下做形態的探討。 PS111-b-PMSMA32成功的使用原子轉移自由基聚合法製備。在PS選擇溶劑之下(THF、EA)，主要出現實心球(sphere)及微胞結構(vesicle)的形態，其中vesicle的結構在高比例的選擇性溶液下才會出現。此外，在PMSMA選擇溶劑下(methanol)出現LCMs及sphere的結構。LCMs可能是primary 或是reverse micelle的二次聚集所造成。 線性PS116-b-PDMAEMA15在單一溶劑之下，藉由在micelle外層的corona排斥力和core的大小決定形態。在THF下，micelle外層corona間的排斥力作用比core 的伸展作用強，出現sphere的形態；增加溶劑的親水性時，減小micelle外層corona間的排斥力作用，形態會從在1,4-dioxane下的vesicle轉變為在DMF下的LCMs。PDMAEMA選擇溶劑中，使用THF及1,4-dioxane為共同溶劑，觀察兩種構形下皆以LCMs及碗狀為主要出現的結構，但在以DMF為共同溶劑系統中，則不會出現碗狀結構，溶劑的親和力是影響碗狀結構的生成的因素。PDMAEMA具有對pH敏感性，因而在線性PS116-b-PDMAEMA15在pH=3.1溶液下生成層狀(lamellae)，轉變成在pH=7.0的sphere再轉變成pH=11.5球狀聚集的結構。雜臂星形PS6-PDMAEMA6在pH=3.1溶液下生成sphere，pH=7.0轉變成聚集的形態，而在pH=11.5則因產生沉澱沒有明顯的形態，原因在於雜臂星形(heteroarm)的構形比較受到限制且pH=11.5之下PS及PDMAEMA皆為疏水鏈段。此外，線性PS116-b-PDMAEMA15及雜臂星形 (heteroarm) PS6-PDMAEMA6在加熱和冷卻的過程會有形態上的改變，且線性PS116-b-PDMAEMA15在1,4-dioxane溶劑下，初步的研究觀察到形態具有可逆性。

Amphiphilic block copolymers have been extensively studied recently. They can not only be prepared by versatile synthetic approaches but also have multiple morphologies generated from its different chemical interaction between two blocks or environment. In this study, amphiphilic block copolymer with one block of PS and another environmental-sensitive block of Poly[3-(trimethoxysilyl)propyl methacrylate] (PMSMA) or Poly [2-(dimethylamino)ethylmethacrylate] (PDMAEMA) were successfully synthesized by atom transfer radical polymerization. Besides linear architecture, heteroarm star copolymer PSn-PDMAEMAn was also synthesized and characterized. Two issues will be addressed in the thesis: (1) correlation of morphology of linear PS-b-PMSMA with PS/PMSMA selective mixed solvent; (2) correlation of morphology of linear PS-b-PDMAEMA and heteroarm PSn-PDMAEMAn star polymer in PDMAEMA selective mixed solvent and different pH and temperature. Polystyrene-block-poly[3-(trimethoxysilyl)propyl methacrylate] was successfully prepared by the ATRP method. The spherical morphology was mostly observed in different ratio of anisole/PS-selective solvent (THF and EA) but vesicle was obtained at a very high volume ratio. On the contrary, the morphologies observed at PMSMA selective solvent of anisole/methanol system are mainly LCMs and spheres. The morphology of LCMs could be due to secondary aggregation of primary micelles or reverse micelle. For linear PS116-b-PDMAEMA15 in pure solvent, the corona repulsion force and the core dimension determined the morphology. In THF solvent, the corona repulsion force was dominant and thus the sphere morphology was observed. With increase hydrophilic characteristic of the solvent, the corona repulsion force decreased and the vesicle morphology in 1,4-dioxane and large compound micelles in DMF were observed. For both architectures, the large compound micelles and bowl-shape micelle is mainly observed in PDMAEMA selective solvent using THF and 1,4-dioxane as the common solvents but the bowl-shape cannot be observed in DMF common solvent. It suggests that the common solvent affinity with both blocks is an important factor to form bowl-shape morphology. For linear PS116-b-PDMAEMA15, the morphologies change from lamellae (pH=3.1) to sphere (pH=7.0) and to sphere aggregates (pH=11.5) because of the pH-sensitivity of PDMAEMA segment. For star PS6-PDMAEMA6, the morphologies changes from spherical-like (pH=3.1) to large aggregate (pH=7.0), and to featureless aggregates (pH=11.5). The confined structure of PS6-PDMAEMA6 heteroarm star copolymers have both hydrophobic PS and PDMAEMA aggregated in the core caused the precipitation and featureless morphology of in pH=11.5 solution. Besides, the effect of the heating and cooling process could result in a significant morphology change for both linear and heteroarm PS6-PDMAEMA6. A preliminary study suggests that a reversible morphology change is obtained in 1,4-dioxane solvent.