低世代雙親性樹枝狀分子之超分子化學與奈米技術

Abstract

本研究於發展低世代雙親性樹枝狀分子（PAD1與PAD2），以季戊四醇（Pentaerythritol）為核心單元，外圍修飾上四隻雙親性手臂（Amphiphilic arm）；即內層親水核/外層疏水殼之雙性結構。PAD1的疏水片段以剛硬的苯環結構鍵結十二烷基；而PAD2的疏水片段則以較柔軟的sp3碳（Carbon, C）所鍵結。

壹. 以聚合反應製備軟性奈米柱於雙親性樹枝狀分子 以PAD1為例，將其作為奈米反應器（Nano-reactor），藉由親水單體（Hydroxyethyl methacrylate, HEMA）聚合，以產生大小均一奈米柱，此粒子為雙親性樹枝狀分子內含親水性聚甲基丙烯酸甲酯、末端疏水脂鏈的雙親性奈米柱（PAD1-NPs），以核磁共振（NMR）、凝膠滲透層析儀（GPC）、場脫附法質譜儀（FD-MASS）與小角度X光散射（SAXS）等鑑定證實此粒子的成功製備。溶液相SAXS實驗進行分子形貌的分析，結果顯示聚合所得的奈米柱（Nano-cylinder）其直徑為1.9 nm、長度為4.0 nm。所製備之雙親性奈米粒子－PAD1-NPs，擁有獨特的柱狀結構，並突破傳統乳化聚合之粒子下限，發展雙親性樹枝狀分子相關知識及開拓其在奈米科技之新應用。

貳. 不同連接基之雙親性樹枝狀分子對主客化學效應之探討 透過分子的設計與合成（PAD1與PAD2），探討具有不同疏水連接基團PAD1和PAD2分別對於客體自組裝與結構上的變化。溶液態SAXS結果顯示PAD1與PAD2在低濃度時為不定型，添加溶劑後會與其共組裝成奈米柱。固態XRD鑑定結果顯示當EtOH/H2O (v/v = 9/1) 溶劑覆蓋於PAD1薄膜表面時，會破壞PAD1六方晶格的排列；反之，PAD2會因親水客體的協助而維持特定構型，由無序相轉為有序的液晶相。我們期望本研究能累積並建立深厚的專業知識，未來作為突破低世代雙親性樹枝狀分子在各項運用瓶頸之深厚基礎。

In this research, low generation amphiphilic dendrimers, PAD1 and PAD2, which have inner hydrophilic core and outer hydrophobic shell, were first successfully synthesized by connecting a pentaerythritol core with four amphiphilic arms. The difference between PAD1 and PAD2 is the joint fragment connecting hydrophilic core and hydrophobic linker. In PAD1, the two parts are bonded by a rigid and planar benzene ring, whereas in PAD2, they are bonded by a more soft and non-planar sp3 carbon(C). Part 1. Preparation of Soft Nano-Cylinders via Polymerization in Amphiphilic Dendrimers The molecule was used as a nano-reactor to produce uniform polymer particles because the core provides cavity to encapsulate hydrophilic guest molecules. By polymerizing hydrophilic (hydroxyethyl)methacrylate (HEMA) in the PAD1, amphiphilic nano-cylinders, denoted as PAD1-NPs, which contain hydrophilic poly(HEMA) body and hydrophobic aliphatic tips, were produced. NMR spectra, GPC, MASS and SAXS characterizations were used to confirm that the PAD1-NPs were produced via nano-emulsion polymerization. Moreover, the SAXS results show that PAD1-NPs are uniform nano-cylinders with diameter of 1.9 nm and length of 4.0 nm. The concept of nano-emulsion polymerization thus breaks the lowest size limitation of the conventional emulsion polymerization and facilitates the formation of unique amphiphilic polymer nano-particles(PAD1-NPs). Part 2. Influences of Linker Units on the Self-Assembled Morphology of Amphiphilic Dendrimers In this part, encapsulation behavior of the amphiphilic dendrimers with different hydrophobic linker group, PAD1 and PAD2, was studied. This research reveals the self-assembly behavior of PAD1 and PAD2 with different solvent as guest. SAXS results reveal the similar solution topological behavior that both micelles exhibit non-specific shape. After encapsulating guest molecules, they turn into cylindrical micelles. Solid-state XRD results reveal the opposite assembly behavior after solvent added. With added solvent, PAD1 turns from hexagonal columnar phase into a disordered phase, whereas, for PAD2, the added solvent turns the amorphous PAD2 into ordered LC phase.