Novel Aromatic Polyimide-Nanocrystalline-Titaniaybrid Optical Films with High Refractive Index
Date Issued
2009
Date
2009
Author(s)
Lin, Po-Han
Abstract
Aromatic polyimides are well known as excellent heat-resistant and high refractive index materials which have been widely investigated and applied for optoelectronic devices. However, their applicability has been limited because of the normally insolubility and infusibility in the fully imidized form. The incorporation of hydroxyl groups on the backbones of the polyimides was an important strategy to ensure the solubility and provided the reactive sites for organic-inorganic bonding. Composites that consist of polymer–inorganic hybrid materials have recently attracted considerable interests due to their enhanced mechanical, thermal, optical properties compared to the corresponding individual inorganic or polymer component. The research goals of this thesis were design and synthesis of novel polymer/titania hybrid materials and investigated their applications in optical films. Furthermore, the lower colorness, high optical transparency, and high refractive index optical films could also be prepared.hapter 2 included two series of novel soluble polyimides with hydroxy-substituted which were synthesized from the new diamines, 2,3-bis(4-amino-3-hydroxyphenoxy)naphthalene and 2,7-bis(4-amino-3-hydroxyphenoxy)naphthalene, with various commercial tetracarboxylic dianhydrides, respectively. High refractive index polyimide–titania hybrid optical films were successfully prepared from the soluble hydroxy-substituted polyimides and titanium butoxide by controlling the organic/inorganic molar ratio. The tunable refractive index (1.67-1.99) of hybrid thin films (100-500 nm) could be obtained by controlling titania content. Moreover, the thick titania hybrid films could also be achieved even with the relatively high titania content as high as 50 wt%. To the best of our knowledge, the refractive index and titania content are the highest to date among the polymer–titania hybrid optical films (20-30 µm in thickness). All these obtained hybrid thick films revealed excellent thermal properties with low CTE, good mechanical properties and flexibility, high refractive index, and good optical transparency in the visible region.hapter 3 showed the effective approach of improving the solubility of aromatic polyimides by incorporation of the hexafluoroisopropylidene (6F) and hydroxyl groups into polymer backbone. High refractive index and optical transparency polyimide–titania hybrid optical films were also successfully prepared. The refractive index (1.61-1.99) of hybrid thin films (100 nm-1000 nm) could be obtained by tuning titania content, and the hybrid thick films (20-30 µm) also exhibited enhanced mechanical properties and good flexibility, excellent thermal properties with lower CTE, high refractive index, and good optical transparency in the visible region.
Subjects
polyimide
titania
hybrid
high refractive index
optical films
Type
thesis
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