Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/3413
標題: 利用水面塗佈製備奈米圖案成形模板
Nanopatterning of polystyrene-b-poly(L-lactice) diblock copolymer from water surface
作者: 蕭微甄
關鍵字: 高分子團聯共聚合物;block copolymer;奈米圖案成形模板;定向;生物可分解;水面塗佈;Langmuir-Blodgett 法;nanopattern;orientation;biodegradable;Langmuir-Blodgett Method
出版社: 化學工程學系
摘要: 
由於高分子團聯共聚合物具有自組裝(self assembly)形成有序微結構之特性,並且結構尺寸約在數十奈米之間,本實驗室利用聚苯乙烯聚左旋乳酸雙團聯共聚合物(polystyrene-b-poly(L-lactide), PS-PLLA)薄膜製備奈米圖案成形模板,建立由團聯共聚合物自組裝所建構之奈米圖案成形技術之開發。由於團聯共聚合物進行微觀相分離時,極容易產生邊界問題而導致微結構方向不一致之結果,此現象在實際應用上是不被允許的。因此製備無缺陷且具有大範圍有序排整定向的奈米圖案成形模板為應用上的關鍵技術。
由於旋轉塗佈技術形成的薄膜具有良好的均勻性,所以在一般製程技術上最常被使用。本實驗室先前利用旋轉塗佈之方式作為奈米圖案製程,並發現在塗佈的過程中,溶劑的揮發誘導微結構呈現有序排整。並進一步探討微結構之形成與變因,如溶劑之揮發速率與溶劑與團聯共聚合物之溶解度等。經由實驗結果顯示必須選用適當揮發速率的選擇性溶劑將可誘導微結構呈現垂直於基材的大範圍排列。但是使用旋轉塗佈製備模板之方法只能成膜於表面平整的平板基材上如載玻片、碳膜、銦錫氧化物玻璃、Si Wafer …..等。但是對於類似球體、橢圓體或是生醫常使用的多孔性材料(例如:可植入血管中之補綴片)….等形狀較特殊的基材,我們無法利用旋轉塗佈的方式製備所需要的模版。而且利用旋轉塗佈製備模板由於使用不同的基材容易產生界面效應。所以我們採用類似Langmuir- Blogett Film的成膜機制進行本實驗。由於LB Film的成膜機制導致使用的雙團聯共聚合物其一端必須擁有親水基而另一端為疏水基。本實驗則利用水與溶劑之界面張力成膜,經由溶劑的揮發過程誘導微結構進行排整。當溶劑完全揮發後,薄膜可轉移至我們所需要的基材上進行微結構形態鑑定。經由實驗結果觀察發現選用揮發速率適中的溶劑並利用水的界面張力成膜將可誘導團聯共聚合物圓柱微結構呈現大範圍排整並垂直於水面之排列,即形成垂直形態的微結構。
本實驗進一步探討影響微結構形成或排整之變因,如溶劑與水產生之界面張力、溶劑之揮發速率、溶劑與團聯共聚合物之溶解度、溶劑與水的可溶性等。根據實驗結果顯示:(1) 溶劑與水之界面張力只影響高分子薄膜之成膜與否,並不影響微結構之排整或定向。(2)若利用揮發速率較緩慢的溶劑由於形成的薄膜其表面粗糙度過大而形成無序的微結構。反之,若利用揮發速率較快的溶劑亦呈現無序的形態,此現象是由於溶劑之揮發速率過於快速導致微觀相分離尚未形成之前溶劑已揮發完畢。(3)若使用不同揮發速率之中性溶劑利用水面成膜所形成之團聯共聚合物薄膜均為無序之形態。(4)若溶劑與水的可溶性佳,在成膜的過程中,溶劑將會溶於水中而導致無法成膜。由上述的實驗結果證實欲製備大範圍排整且垂直於基材排列之圓柱微結構,選用揮發速率適中且微溶於水的選擇性溶劑為必要條件。此外,為了符合多元化的應用價值,我們亦針對團聯共聚合物薄膜厚度做調控。我們分別利用溶液濃度、容器直徑及水溫進行控制。由實驗結果得知薄膜厚度與溶液濃度和水溫呈現正變的關係,而與容器直徑呈現反變的關係,並且經由影像觀察皆呈現圓柱垂直於基材排列之形態。
由於奈米圖案模板的耐熱溫度約在主相的玻璃轉化溫度左右,以PS-PLLA為例,其模板的耐熱溫度約在80至900C之間,故利用強氧化劑與PS苯環產生氧化反應而與金屬產生鍵結加強模板的耐熱溫度;由於強氧化劑RuO4會與聚苯乙烯之苯環產生化學交連反應而將重金屬Ru鍵結上去,增強其PS鏈段之耐溫性。
本實驗成功地開發一精準、簡單、快速之奈米圖案成形製程,選擇適當之溶劑製備聚苯乙烯聚左旋乳酸雙團聯共聚合物溶液,藉由水的表面張力塗佈進行微結構垂直形態之定向。藉由其中之一鏈段具生物可分解性,選擇性地利用鹼液水解之方式進行分解反應,成功地製備具高低規則起伏之地形奈米圖案成形模板(topography nanopatterning)。

Nanopatterning from the self-assembly of a series of degradable block copolymers, polystyrene-b-poly(L-lactide) (PS-PLLA), with PLLA hexagonal cylinder (HC) morphology, has been carried out. By selecting appropriate solvent for solution casting from water surface, the formation of large-size, oriented microdomains of PS-PLLA thin films where the axis of HC morphology is perpendicular to the substrate (i.e., perpendicular morphology) was successfully achieved. The mechanism of induced-orientation is attributed to the evaporation rate control of solvent, and the solubility of solvent with PS-PLLA and water. Low solvent evaporation rate gives rise to form randomly oriented microdomains having rough surface, and high solvent evaporation rate limits the formation of phase separation. The effect of solvent miscibility is also critical to the formation of oriented microdomains. The use of neutral solvent for the PS-PLLA causes the random orientation, and the PS-PLLA studied is not dissolved in PLLA selected solvent. Beside the effect of solvent evaporation and solvent miscibility, the effect of solubility of solvent with water is also important. If solvent can be dissolved with water, the formation of uniform thin films will be interrupted.
Different PS-PLLA thin films ranging from tens nanometers to hundreds nanometers were obtained at controlled casting conditions such as solution concentration, container diameter and water temperature. Regardless of changing thickness, well-oriented microdomains were obtained. Topographic nanopatterns having periodic arrays of cylindrical nano-channels were successfully created after the treatment of NaOH aqueous solution where the PLLA component was hydrolytically degraded. By controlling molecular weight of block copolymers, topographic nanopatterns having nano-channels as small as ten nanometers in diameter were prepared so as to establish a wonderful platform. The large-size, well-oriented, topographic nanopatterns with tunable film thickness can be obtained, and then transferred to different substrates, particularly curvature or porous substrate., so as to give promising opportunities for block copolymer applications in the fields of nano-sciences.
URI: http://hdl.handle.net/11455/3413
Appears in Collections:化學工程學系所

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