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標題: | 以表面改質及分散技術製備高折射率有機/無機奈米複合材料 Fabrication of High Refractive Index Organic/Inorganic Nanocomposite via Surface Modification and Dispersion Technique |
作者: | Kuo-Hsin Chang 張國馨 |
指導教授: | 林唯芳(Wei-Fang Su) |
關鍵字: | 折射率,有機/無機奈米複合材料,溶膠-凝膠法,原子力顯微鏡,表面型態,玻璃轉移溫度,二氧化鈦,二氧化矽, refractive index,organic/inorganic nanocomposites,sol-gel,AFM,surface morphology,glass transition temperature,titanium dioxide,silica dioxide, |
出版年 : | 2006 |
學位: | 碩士 |
摘要: | 由於高折射率材料有廣泛的應用性,如光波導材料(Optical waveguide)與光學鏡片等,因此我們製備高折射率材料。
為了達到奈米複合材料之折射率大於1.6的目標,本論文分成四個部分:首先,藉由改變不同的高分子與二氧化矽之重量比以了解折射率隨著重量組成而改變的情形。結果發現材料的折射率會隨著二氧化矽含量的增加而下降。這是由於二氧化矽本身的折射率較低,因此製備成奈米複合材料後導致整體折射率降低。雖然在此階段中無法達成高折射率的目標,但是經由材料的熱性質以及機械性質的分析後發現到一個很有趣的現象,就是當二氧化矽含量達40 wt%後,這兩種物性皆呈現非線性的上升。因此嘗試藉由原子力顯微鏡(AFM)觀察材料表面型態(surface morphology),希望能藉由微觀尺度來探討表面型態與材料物性之關連性。結果亦發現當二氧化矽含量達40 wt%後,奈米粒子在高分子母體中呈現有序規則排列,這樣的網狀(network)結構就侷限住高分子的移動,因此造成材料的Tg、硬度以及Young’s modulus皆呈現非線性上升。由此可知二氧化矽含量40 wt% 為此系統之percolation threshold。 此外。我們以AFM搭配臨場(in-situ)加熱附件並藉由影像分析軟體找出不同無機含量下混成材料的表面玻璃轉移溫度(Tg, surface),將結果與DSC及TMA所得Tg比較。我們發現當二氧化矽奈米粒子含量達40 wt%後,DSC與TMA皆無法測得其Tg,但是仍然可由臨場加熱AFM測得。這是由於AFM探針較TMA小許多,因此可偵測出材料表面細微的變化。 在第二個部分中,以外層包覆矽氧烷類之非晶型(amorphous)二氧化鈦與EOBDA (ethoxylated (3) bisphenol A diacrylate) 製備出奈米複合材料,其折射率隨著二氧化鈦量的增加而上升。當二氧化鈦含量為15.6 wt%時,在波長為633 nm情況下之折射率可由1.5648增加至1.6161;並且於850 nm、1310 nm與1550 nm的光穿透度皆達93%以上。 在第三個部分中,以油酸(oleic acid)進行表面改質所製備的銳鈦型(anatase)二氧化鈦與BMAEP(Bis[2-(methacryloyloxy)ethyl] phosphate)及EOBDA壓克力單體混合後,製備出奈米複合材料,當二氧化鈦含量達7.9 wt%時,折射率由1.5443上升到1.5553,上升幅度並不明顯。這是由於二氧化鈦奈米粒子表面的油酸含量很高,以致於折射率上升的幅度受限。 在最後一個部分中,以醋酸表面改質之銳鈦型二氧化鈦奈米複合材料與BMAEP壓克力單體混合後,製備出奈米複合材料。當銳鈦型二氧化鈦固含量達35.4 wt%後,折射率即由1.5020上升至1.6071。此外,在波長為850 nm、1310 nm與1550 nm下的光穿透度分別為87.4 %、94.3 %及94.0 % 。 Due to the wide application of high refractive index materials (e.g. optical waveguide and optical lenses, etc.), we synthesized high refractive index materials. In order to reach the goal of high refractive index (RI) 1.6 at 633 nm, we tried to synthesize four kinds of nanocomposites. First, we prepared silica-polymer nanocomposites. By changing the silica content, we can realize how the silica content influences the RI. However, we found that the RI decreased when the silica content increased. It is because the RI of silica is lower than that of the polymer matrix. In spite of the fact that we can’t reach the goal by this method, we found an interesting phenomenon after analyzing the mechanical and thermal properties of the nanocomposites. We found that both of the mechanical and thermal properties increased nonlinearly when the silica content reached 40 wt%. In order to explain this nonlinear phenomenon, we used atomic force microscopy (AFM) to obtain the surface morphology of nanocomposites and tried to find the correlation between their physical properties and surface morphology. We found that the silica nanoparticles in the polymer matrix became self assembled when the silica content reached 40wt%. The network formation of the silica nanoparticles confines the moving of polymer and causes the increasing of their physical properties nonlinearly. Accord to these results, we made the conclusion that the percolation threshold of this hybrid system is 40 wt% of the silica content. In addition, we used AFM with the thermal accessory to find in-situ nanocomposites surface morphology and then used image processing software to know specifically the temperature influence on its topography. Thus we obtained the nano scale Tg and made comparison with the macro scale Tg, which was obtained from DSC and TMA. From the results, we found that both DSC and TMA can’t find their Tg when the silica content reaches 40%. However, we can still find that it is increasing by AFM. It is because the AFM probe is much smaller than TMA probe, so we can still find their Tg. In part two, we synthesized an amorphous TiO2 nanoparticle colloid solution and mixed it with EOBDA (ethoxylated (3) bisphenol A diacrylate) monomers after surface modification of TiO2 nanoparticles by the coupling agent (3-(trimethoxysilyl) propyl methacrylate, MPS), then we used the resulting materials that were the product of the above stated reactions to fabricate nanocomposites. We found that RI increased from 1.5648 (EOBDA) to 1.6161 after adding 15.6 wt% of titania and the transparency in the wavelength of 850 nm, 1310 nm and 1550 nm were above 93%. In part three, we synthesized of oleic acid-capped anatase TiO2 nanocrystals, then mixed them with BMAEP (Bis[2-(methacryloyloxy) ethyl] phosphate) and EOBDA monomers to fabricate nanocomposites. We found that RI increased from 1.5443 (BMAEP/EOBDA mixing) to 1.5553 after adding 7.9 wt% of titania. It is clear that the range of RI increasing is not as high as it in part two. It is because there is too much surfactant around titania to increase the RI using pure TiO2. Finally, we used carboxylic acid-capped anatase TiO2 nanocrystals, and mixed them with BMAEP to fabricate nanocomposites. We found that RI increased from 1.5020 (BMAEP) to 1.6071 after adding 35.4 wt% of titania and the transparency in the wavelength of 850 nm, 1310 nm and 1550 nm to be 87.4 %, 94.3 % and 94.0%, respectively. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/25839 |
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顯示於系所單位: | 材料科學與工程學系 |
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