高分子薄膜受限於陽極氧化鋁模板內奈米孔洞之不穩定現象

Abstract

此論文主要探討聚苯乙烯 (polystyrene, PS) 薄膜受限於陽極氧化鋁 (anodic aluminum oxide, AAO) 模板內奈米孔洞的退火誘導之不穩定現象，根據雷利不穩定 (Rayleigh instability) 理論和不同的熱退火條件，受限之PS奈米結構會轉變成波動狀結構 (undulated structures)、雷利不穩定結構 (Rayleigh-instability-induced structures)、或奈米柱結構。 研究工作分成七個部分。第一個部分透過溶液潤濕法將高分子導入AAO模板後製備受限PS奈米管後進行熱退火處理，依據熱退火條件與結構之關係建立形貌圖 (morphology diagram) 以闡述形貌轉變的機制與分子量效應，此外，還將不穩定行為量化統計，討論理論值和實驗值偏差的可能原因。 為了將影響形貌轉變因素探討清楚，第二部分透過不同濃度PS溶液製備管壁厚度相異的奈米管以討論厚度效應，並建立形貌圖與量化統計說明受限PS奈米管經雷利不穩定理論轉變形貌的行為偏差之主要原因。 第三部分則是透過溶劑蒸氣誘導潤濕法製備受限之PS奈米管，討論分子構形 (conformation) 對形貌轉變的影響，並以Good & Girifalco所提出的介面張力計算方式輔助說明構形與張力之關係。 第四部分則是在受限之PS奈米管系統中引入非溶劑的乙二醇 (ethylene glycol, EG) 進行熱退火處理，討論其不穩定行為和形貌轉變機制。 第五部分用烷基三氯矽烷與帶有羥基的AAO模板表面行自組裝單層膜反應，使親水性AAO模板轉變成疏水性的AAO模板，討論不同碳鏈數烷基三氯矽烷表面改質效果，並且展示此疏水性奈米孔洞模板於油/水分離的應用潛力。 除雷利不穩定之外，在第六個部分也討論另一種高分子不穩定行為─反潤濕 (dewetting)。控制高分子溶液濃度以製備不同厚度的聚甲基丙烯酸甲酯 (poly (methyl methacrylate), PMMA) 薄膜於疏水性模板孔洞中，經熱退火後可製備出高分子奈米半球，並討論其反潤濕行為模式。 最後一個部分是在一個非受限系統中，透過線斷法 (breaking thread method)討論不同高分子黏度比對雷利不穩定的影響，並且藉由分析材料形貌轉變過程計算出不穩定行為的成長速率 (growth rate) 與不同溫度條件下之介面張力。

This work investigates the annealing-induced instability of polystyrene (PS) thin films coated in the nanopores of anodic aluminum oxide (AAO) templates. According to the theory of the Rayleigh instability, PS nanotubes transform into undulated structures, Rayleigh-instability-induced structures, or nanorods under different annealing conditions. This thesis is divided into seven parts. In the first part, we study the annealing-induced instability of confined PS nanotubes fabricated by a solution-wetting method. Based on the correlation between the morphologies and the annealing conditions, we construct morphology diagrams to elucidate the mechanism and the effects of different molecular weights. In addition, quantitative studies of the transformation process are performed. The discrepancies between the experimental values and the theoretical values are also explained. To clarify the factors of the transformation process, in the second part, we study the effect of the wall thicknesses of PS nanotubes using solutions with different concentrations. The discrepancies of the instability behavior are explained by constructing morphology diagrams and performing quantitative studies. In the third part, we study the effect of the polymer conformation by fabricating PS nanotubes with a solvent-vapor-induced-wetting method. The relationship between the polymer conformation and the interfacial tension is explained by an equation proposed by Good and Girifalco. In the fouth part, instability studies are performed by annealing the samples in the presence of ethylene glycol to discuss further the instability behavior and the mechanism of the transformation process. In the fifth part, the hydrophilic surfaces of prestine AAO templates are modified by the self-assembly monolayer method with different alkyltrichlorosilane derivatives and the surface property transforms into hydrophobic. The wetting mode of alkyltrichlorosilanized AAO templates is studied, and the potential for separation of oil/ water mixtures is demonstrated. In addition to the Rayleigh instability, the dewetting behaviors of poly (methyl methacrylate) (PMMA) thin films coated in the nanopores of modified AAO templates are also investigated. In the sixth part, we fabricate the polymer nano-hemispheres and discuss the different dewetting modes using polymer thin films with different thicknesses. In the last part, we study the effect of polymer viscosity ratio of non-confinened Rayleigh instability (breaking thread method) by analyzing the transformation processes induced by thermal annealing. Furthermore, the interfacial tensions between both polymers at different temperatures can be inferred by the growth rates of the instability.