硫醚聚醯亞胺材料及聚醯亞胺/氧化矽混成材料光學膜之合成與性質鑑定

Abstract

聚醯亞胺為傳統高性能高分子，已經被廣泛運用在各個產業之中。然而開發具有高折射率、高透明性和優良熱機械性質之高分子基材仍具挑戰性。本論文藉由分子設計以及有機無機混摻進而合成出兼具高折射率及良好穿透度的光學膜，茲敘述如下： 本研究利用合成出來的兩種高含硫量二硫醇單體，藉由麥可聚加成反應，和雙馬來醯亞胺獲得色淡的聚醯亞胺硫醚，PITEDT跟PITEMD。透過低溫聚合反應避免黃化，可以合成出白色的高分子；同時，導入大量的硫以及聚醯亞胺官能基在高分子中，可用於提高折射率卻又不會導致阿貝數降到太低造成色散。這兩種高分子所製備的光學薄膜，具有高折射率(> 1.71 )、高穿透度(> 95% at 400nm)以及不低的阿貝數(> 22)。 其次合成一系列色淡含羥基聚醯亞胺，以及氧化矽混成材料所的合成製備出可彎曲的光學膜。 本研究透過含六氟異丙烯官能基的雙胺以及含醚基、六氟異丙烯基、叔丁基的雙酸酐合成一系列聚醯亞胺，6FOXPI、6F6FPI、6FDBPI；導入這類官能基，可增加聚醯亞胺自由體積，以提高光穿透度、溶解度和膜的可彎曲性。同時聚醯亞胺內的羥基和矽酸四甲基酯型成共價鍵，使混成氧化矽顆粒可均勻分散在聚醯亞胺內。藉由穿透式電子顯微鏡照片可以得知本研究製備之混成材料，氧化矽顆粒在8~12奈米可將光散射損失降至最低。由於奈米等級分散的氧化矽顆粒與聚醯亞胺分子內耦合形成類似交聯結構，可進一步提升聚醯亞胺的熱性質與機械性質，隨著混摻氧化矽的比例上升，可使聚醯亞胺光學膜的熱膨脹係數大幅下降到55 ppm/oC 以下，玻璃轉換溫度提升到300 oC以上，熱裂解溫度提升到400 oC以上，以及在厚膜(> 25 μm)的狀況下保有良好的穿透度(> 80% at 400nm)。

Polyimides are high performance and functional polymers used in different fields. However, the development of polimides with high refractive index, optical transmittance, and superior thermal-mechanical properties remain challenges. In this thesis, high refractive index and high optical transparency polyimides and their optical films were synthesized by molecular design and hybrid technology as following: In this study, we synthesized the two dithiol monomers and then polymerized with bismaleimide by Michael addition under low temperature to get the colorless polyimidothioether, PITEDT and PITEMD.The materials have high refractive index and moderate Abbe’s number because of the high sulfur content and aromatic imide functional group in these polyimidothioether. The prepared optical thin films of these two polymers have high refractive index (> 1.71), excellent transparency (> 95% at 400nm) and moderate Abbe’s number (> 22). Secondly, three colorless polyimides with hydroxyl group, 6FOXPI, 6F6FPI and 6FDBPI. The hybrid optical flexible optical films of these polyimides with different silica oxide content have successfully synthesized.In this study, hexafluoroisopropylidene, ether and t-butyl groups are used to increase the free volume of the polyimides, thereby improving the optical transparency, organic solubility and flexibility. Tetramethyl orthosilicate was used to form a covalent bond between silicon oxide and the hydroxyl group of the polyimides. By this method, it was found that the particle were well dispersed and the size of silicon oxide is 8~12nm which can avoid the light scattering. By forming the intramolecular coupling crosslink bond between the silica and polyimides, these hybrid films have better thermal and mechanical properties. These hybrid optical films have much lower coefficient of thermal expansion (< 55 ppm/oC), high TS (> 300 oC) and high Td (> 400 oC) and good optical transparency (> 80% at 400nm, thickness > 25 μm ).