Fabrication of High Refractive Index Organic/Inorganic Nanocomposite via Surface Modification and Dispersion Technique
Date Issued
2006
Date
2006
Author(s)
Chang, Kuo-Hsin
DOI
zh-TW
Abstract
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.
Subjects
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
Type
thesis
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