團聯聚合物於陽極氧化鋁孔洞模板中之形貌控制與應用

Abstract

近年來，聚合物奈米材料之相關研究蓬勃發展，其中以團聯聚合物（Block copolymer）之研究最受到矚目，因其具有自組裝之特性，故可排列成規則之奈米結構。然而，此類材料在孔洞受限環境下之機理仍尚未清楚。本研究使用之團聯聚合物為含聚苯乙烯-聚二甲基矽烷 （polystyrene-block-polydimethylsiloxane, PS-b-PDMS）搭配陽極氧化鋁（Anodic aluminum oxide, AAO）孔洞模板，進行溶劑蒸氣退火（Solvent vapor annealing）反應，以得到之奈米結構。其中，溶劑蒸氣退火法可避免熱裂解與在AAO表面形成聚合物膜。此外，PS-b-PDMS之奈米結構可經由改變潤濕條件進而加以控制。 在本論文之第一章中，首先介紹團聯聚合物特性、孔洞受限效應以及製備AAO模板之方法。接著，在第二章介紹本研究中所使用到的藥品以及分析鑑定儀器。本研究之實驗結果主要分為四個部分。第一部分（第三章）探討三種溶劑蒸氣（甲苯、正己烷以及混合溶劑）對團聯聚合物在AAO孔洞中形貌之影響。同時，也可利用氫氟酸溶液對PDMS鏈段進行選擇性移除，進而得到具有孔洞之PS奈米結構。 延續第一部分之實驗內容，因第一部分未詳盡探討不同比例之混合溶劑對形貌之影響，故在第二部分（第四章）將混合溶劑之比例進行細分，由結果發現其形貌可藉由改變溶劑比例達到改變形貌之效果。此外，還可利用不同溶劑進行多次溶劑蒸氣退火反應，將原先已在AAO中所形成之奈米結構加以反覆轉換，在實驗中形貌轉換次數可高達四次。在第三部分（第五章）中，將探討在受限效應下對團聯聚合物形貌之影響。在實驗中，使用三種不同大小之AAO模板，其中孔徑各為 ~200 nm、 ~60 nm以及 ~30 nm。由結果發現在小孔徑模板中，受限效應之影響大於溶劑效應。 在第四部分（第六章）中，我們發展一新的三維奈米遮罩蝕刻策略。其方法為，將團聯聚合物奈米結構作為蝕刻之遮罩，利用氫氟酸選擇性移除PDMS鏈段。當PDMS鏈段完全移除後，氫氟酸會繼續蝕刻PS未覆蓋之AAO孔洞表面，因此，可在AAO彎曲之管壁上形成特殊奈米紋路。而此蝕刻過之AAO模板，可再次當作模板重新填入其他材料，進而製作出表面具有特殊紋路之奈米材料。在本論文最後一章（第七章）中，將對上述幾章之實驗結果進行總結，並提出幾項未來可繼續研究之方向。

Block copolymers have been extensively studied over the last few decades because they can self-assemble into well-ordered nanoscale structures. The morphologies of block copolymers in confined geometries, however, are still not fully understood. In this study, we investigate the fabrication and morphology characterization of polystyrene-block-polydimethylsiloxane（PS-b-PDMS） block copolymers confined in the nanopores of anodic aluminum oxide（AAO） templates. We observe that the block copolymers can wet the nanopores using a novel solvent-annealing-induced nanowetting in templates method（SAINT）. The unique advantage of this method is that the problem of thermal degradation can be avoided. In addition, the morphologies of PS-b-PDMS nanostructures can be controlled by changing the wetting conditions. In this thesis, we first introduce the concept of block copolymers, the confinement effect, and the fabrication of AAO templates（Chapter 1）. Then the experimental materials and characterization instrument are presented（Chapter 2）. The experimental results are divided into four parts, in which different experimental parameters are controlled. In the first part（Chapter 3）, the effects of three different solvent vapors（toluene, hexane, and a co-solvent of toluene and hexane）on the morphologies of PS-b-PDMS are discussed. Porous PS nanostructures can also be prepared by etching the PDMS domains selectively with HF. Following the first part, we investigate more detail about the co-solvent ratio on the morphology of PS-b-PDMS in the second part（Chapter 4）. We find that the morphologies can be finely tuned by changing the co-solvent ratio. Surprisingly, the solvent-vapor-controlled morphologies can be reversibly switched by annealing the PS-b-PDMS nanostructures in different solvent vapors. The reversible experiments can be repeated up to four times. In the third part（Chapter 5）, we study the effect of the nanopore size by using AAO templates with pore sizes at ~200 nm, ~60 nm, and ~30 nm. The pore size is found to play a more important role than the type solvent does. In the fourth part（Chapter 6）, we develop a three-dimensional mask（3-D mask） strategy using the PS-b-PDMS nanostructures as the etching mask. The HF solution can etch the PDMS domains selectively. Therefore, the surface of the uncovered AAO walls can be further etched, resulting in the formation of nanopattern on the curved AAO walls. The etched AAO membranes can again be used as templates for making PMMA nanostructures. In the last chapter（Chapter 7）, we summarize the all the experimental results and propose some future works. Block copolymers have been extensively studied over the last few decades because they can self-assemble into well-ordered nanoscale structures. The morphologies of block copolymers in confined geometries, however, are still not fully understood. In this study, we investigate the fabrication and morphology characterization of polystyrene-block-polydimethylsiloxane（PS-b-PDMS） block copolymers confined in the nanopores of anodic aluminum oxide（AAO） templates. We observe that the block copolymers can wet the nanopores using a novel solvent-annealing-induced nanowetting in templates method（SAINT）. The unique advantage of this method is that the problem of thermal degradation can be avoided. In addition, the morphologies of PS-b-PDMS nanostructures can be controlled by changing the wetting conditions. In this thesis, we first introduce the concept of block copolymers, the confinement effect, and the fabrication of AAO templates（Chapter 1）. Then the experimental materials and characterization instrument are presented（Chapter 2）. The experimental results are divided into four parts, in which different experimental parameters are controlled. In the first part（Chapter 3）, the effects of three different solvent vapors（toluene, hexane, and a co-solvent of toluene and hexane）on the morphologies of PS-b-PDMS are discussed. Porous PS nanostructures can also be prepared by etching the PDMS domains selectively with HF. Following the first part, we investigate more detail about the co-solvent ratio on the morphology of PS-b-PDMS in the second part（Chapter 4）. We find that the morphologies can be finely tuned by changing the co-solvent ratio. Surprisingly, the solvent-vapor-controlled morphologies can be reversibly switched by annealing the PS-b-PDMS nanostructures in different solvent vapors. The reversible experiments can be repeated up to four times. In the third part（Chapter 5）, we study the effect of the nanopore size by using AAO templates with pore sizes at ~200 nm, ~60 nm, and ~30 nm. The pore size is found to play a more important role than the type solvent does. In the fourth part（Chapter 6）, we develop a three-dimensional mask（3-D mask） strategy using the PS-b-PDMS nanostructures as the etching mask. The HF solution can etch the PDMS domains selectively. Therefore, the surface of the uncovered AAO walls can be further etched, resulting in the formation of nanopattern on the curved AAO walls. The etched AAO membranes can again be used as templates for making PMMA nanostructures. In the last chapter（Chapter 7）, we summarize the all the experimental results and propose some future works.