軟性電子(Flexible Electronics)的應用中致力於開發輕、薄、可撓性(flexible)、以及高透明度(transparent)的設計，例如軟性印刷電路板(flexible printed circuit, FPC)、液晶顯示器(liquid-crystal display, LCD)、觸控式面板(touch panel)、可撓式顯示器(flexible display)、軟性太陽能底板、以及電子書等，高透明度塑膠材料是必須的，且材料必須要有優良的熱安定與易加工性，才能符合設計上的需求。因為聚醯亞胺薄膜(PI films)具有良好的耐高溫性能、環境穩定性、力學性能以及優良的介電性能，因此在電子產品的材料廣泛應用。
然而，芳香族聚醯亞胺薄膜因電荷轉移效應(charge transfer complex effect)的影響，薄膜呈現黃棕色，所以在光電產業的應用上受到限制。此外，聚醯亞胺的溶解度也影響加工性。為了改善薄膜的透明度以及聚醯亞胺的溶解度，已有相當多的研究提出改善聚醯亞胺透明度以及溶解度的方法。
本研究將利用三種不同的脂肪族二酸酐單體Bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic acid dianhydride (COeDA)、1,2,3,4-Cyclopentanetetracarboxylic dianhydride (CPDA)以及Bicyclooctanete- tracarboxylic dianhydride (BODA)與兩種不同的二胺單體4,4'-(9-Fluorenylidene)dianiline (FDA) 以及2,2-Bistrifluoromethyl benzidine (TFDB)，藉由改變二胺的比例，在無水極性非質子溶劑NMP中進行一步驟熱溶液環化縮聚合反應，合成出不同結構的聚醯亞胺，並針對所合成出的聚醯亞胺進行結構及性質上的分析。

Aromatic polyimides are a class of high temperature polymers with excellent mechanical and chemical properties. They have been extensively studied for many years and are widely used in electrical and electronic industries. In the application of electronic products, such as liquid-crystal displays (LCD), flexible displays, flexible printed circuits, solar cells, and sensors, it is necessary to develop thin, light, flexible, and colorless designs. However, due to their limited solubility and high melting temperatures or glass-transition temperatures, a lack of processability of aromatic polyimides is one of their central drawbacks. In addition to being able to prepare soluble aromatic polyimides, the polyimides also must be transparent.
The goal of our research was to prepare polyimide films that have good solubility and are transparent.
A series of partially aliphatic copolyimides were synthesized in our research. At first, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic acid dianhydride (COeDA), 1,2,3,4-cyclopentanetetracarboxylic dianhydride (CPDA) and bicyclooctanete-tracarboxylic dianhydride (BODA) were used as cycloaliphatic dianhydrides. 4,4'-(9-fluorenylidene)dianiline (FDA) was used as an aromatic diamine. However, the reactivity of dianhydride COeDA, CPDA, and BODA with diamine FDA was too low to prepare films, so we added another diamine 2,2-bistrifluoromethyl benzidine (TFDB), which has a trifluoromethyl structure. Hence, a series of copolyimides were synthesized that were based on various ratios of diamines TFDB and FDA with aliphatic dianhydrides COeDA, CPDA, and BODA. They were synthesized using a one-step chemical solution polycondensation method in NMP with a catalyst (isoquinoline) at 200oC for 24 h. The solubility, thermal properties, mechanical properties, and optical properties of the copolymers were systematically studied. In this study, both the reactivity and solubility increased with increasing amounts of the TFDB diamine monomer. The thermal stability and Tg of the copolyimides increased with increases in the FDA content in the copolyimides. Most of the copolyimides synthesized in this research displayed good solubility in aprotic polar solvents. The UV-vis measurement results showed that all of the synthesized copolyimides exhibited good transparency in the visible region. The synthesized copolymers had a tensile stress in the range of 55-80 MPa and elongation at a break less than 14%.

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