使用模板法製備之多孔性與豌豆形高分子奈米材料

Abstract

由於一維高分子奈米結構可以應用在太陽能電池或是生物感測器等方面的研究，所以近年來引起了相當大的注意。其中一種被廣泛用來製作一維高分子奈米結構的方法為模板法，在此方法中，模板被當作支架使用。雖然模板法已經被用來製作許多不同種類的高分子奈米結構，但是對這些利用模板而成形的高分子奈米結構來說，其性質和形貌的控制仍然是個很大的挑戰。 此篇論文主要的研究分為兩個部分，第一部分在第二章「利用陽極氧化鋁表面誘導之相分離製作多孔性高分子奈米結構」中。在這部分的研究裡，我們主要探討陽極氧化鋁(Anodic Aluminum Oxide, AAO)模板內多孔性高分子奈米結構的形成，此形成主要是經由高分子溶液的表面誘導式相分離而造成。聚甲基丙烯酸甲酯(poly(methyl methacrylate), PMMA)和四氫呋喃(tetrahydrofuran, THF)在此被用來研究表面誘導式相分離的轉變過程。隨著AAO模板浸泡在高分子溶液中的時間變長，富含溶劑微滴的大小會因為粗化的過程而變大，造成多孔性高分子奈米結構的形成。我們還改變了浸泡時間、高分子的濃度、高分子的分子量、以及溶劑的質量等實驗參數來進一步判斷粗化過程的機制。 此篇論文主要研究的第二個部分在第三章「在陽極氧化鋁模板內利用雙溶液潤濕法製作高分子奈米豌豆」中。在此部份的研究裡，我們探討了在AAO模板的奈米孔洞內利用雙溶劑策略而製得的豌豆形高分子奈米結構。首先，我們先將聚苯乙烯(polystyrene, PS)與二甲基甲醯胺(dimethylformamide, DMF)的溶液導入AAO模板的奈米孔洞內，接著再將此樣品浸泡在PMMA與乙酸(acetic acid)的溶液中。因為乙酸和AAO模板的管壁表面有較強的作用力，所以PMMA溶液將會佔據在PS溶液和AAO模板的管壁之間，而PS溶液則會聚集在奈米孔洞的中間區域。在溶劑揮發之後，就可得到類似豌豆形狀的PS/PMMA複合奈米結構。為了進一步確認豌豆形高分子奈米結構的生成，我們還利用了環己烷(cyclohexane)來選擇性移除PS以及乙酸來移除PMMA。此奈米結構的形成過程和雷利不穩定性(Rayleigh instability)有很大的關聯，我們也藉由改變高分子濃度或分子量等實驗參數來研究此結構的形成。此工作不僅提供了一個簡單的方法來製作高分子複合奈米材料並且控制其形貌和尺寸，對於在受限的幾何形狀中高分子和溶劑的作用，也提供了更深入的了解。

One-dimensional polymer nanostructures have attracted great attention because of their applications in different areas such as solar cells or biosensors. To fabricate one-dimensional polymer nanostructures, one of the extensively used methods is the template method, in which the template is used as a scaffold. Although various polymer nanostructures have been prepared by using the template method, it is still a great challenge to control the properties and morphologies of template-based nanostructures. This thesis is divided into two main parts. The first part is included in chapter 2. We study the formation of porous polymer nanostructures fabricated by surface-induced phase separation of polymer solutions in anodic aluminum oxide (AAO) templates. Poly(methyl methacrylate) (PMMA) and tetrahydrofuran (THF) are used to study the evolution process of the surface-induced phase separation. With longer immersion times of the AAO templates in the polymer solutions, the sizes of the solvent-rich droplets are increased by the coarsening process, resulting in the formation of porous polymer nanostructures. The coarsening mechanism is further confirmed by adjusting the experimental parameters including the immersion time, the polymer concentration, the polymer molecular weight, and the quality of solvent. The second part of this thesis is included in chapter 3. We investigate the formation of core-shell polymer nanostructures by using a double solution strategy in the nanopores of anodic aluminum oxide (AAO) templates. A polystyrene solution in dimethylformamide (DMF) is first introduced into the nanopores of the AAO templates. Then the sample is later introduced into a PMMA solution of acetic acid. Because acetic acid has a stronger interaction to the wall surface of the AAO template, the PMMA solution can occupy the place between the PS solution and the walls of AAO templates. The polymer solution is isolated in the center of the nanopores. After the evaporation of the solvent, peapod-like PS/PMMA composite nanostructures are obtained. The peapod-like polymer nanostructures are confirmed by selective removal of the PS using cyclohexane or the PMMA using acetic acid. The formation process of the polymer nanostructures is related to the Rayleigh-instability-type transformation and is further investigated by varying the experimental parameters such as the polymer concentration or the polymer molecular weight. This work not only offers a simple approach to prepare polymer nanocomposites with controllable morphologies and sizes, but also provides a deeper understanding of polymer-solvent interactions in confined geometries.