脂环族二酐和含双键桥环己烷的聚酰亚胺及其逆狄尔斯-阿尔德反应的研究,ACS Applied Polymer Materials

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脂环族二酐和含双键桥环己烷的聚酰亚胺及其逆狄尔斯-阿尔德反应的研究
ACS Applied Polymer Materials ( IF 4.4 ) Pub Date : 2022-12-07 , DOI: 10.1021/acsapm.2c01685
Kai-Cheng Zhong, Jyh-Chien Chen, Shih-Wei Lee, Hsin-Chung Wu

在这项研究中，两种脂环族二酐，bicyclo[2.2.2]oct-7-ene-2- exo ,3- exo ,5- exo ,6- exo ,7-methyltetracarboxylic-2,3:5,6-dianhydride ( MBTA) 和双环[2.2.2]oct-7-ene-2- exo ,3- exo ,5- exo ,6- exo ,7,8-二甲基四羧酸-2,3:5,6-二酐 (DMBTA),通过 Diels-Alder 反应成功合成了在双键桥环己烷结构上含有甲基取代基的化合物。这些具有exo-exo的二酐的化学结构通过核磁共振光谱和 X 射线单晶衍射充分表征构型。脂环族聚酰亚胺由这些二酐和二胺制备，例如 4,4'-氧二苯胺 (4,4'-ODA) 和 2,2'-双（三氟甲基）联苯胺 (TFMB)。与未取代的类似物相比，在双键桥上引入甲基取代基显示出各种性能的增强。这些具有高分子量的聚酰亚胺可以形成柔性、透明和无色的薄膜，在波长 400 nm ( T ₄₀₀ ) 下具有 86-88% 的优异光学透射率和 0.32-0.87 的黄色指数 ( b * )。它们还表现出高热稳定性，降解温度为 5% 重量损失 ( T _d^5%) 在氮气中为 423–447 °C，玻璃化转变温度 ( T _g ) 为 372–417 °C。这些聚酰亚胺非常适合作为柔性电子应用的基材。这些聚酰亚胺在有机溶剂中也表现出优异的溶解性。特别是，PI-MBTA/TFMB 和 PI-DMBTA/TFMB 即使在低沸点溶剂如环戊酮 (CPN) 中也是可溶的，这意味着使用 CPN 作为显影溶剂作为负型光敏聚酰亚胺 (PSPI) 的潜在应用。MBTA 和 DMBTA 桥的双键不能在 1–4.5 kg cm ^{–2的氢气压力下被氢化}以碳载钯为催化剂，在室温下反应 1-5 天。这可能是由于双键上甲基取代基的空间位阻。从模型化合物的结果和强亲二烯体（马来酸酐）的添加，我们得出结论，双键桥接环己烷体系不能在 360 °C 下进行逆狄尔斯-阿尔德反应。

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Alicyclic Dianhydrides and Polyimides Containing Double-Bond Bridged Cyclohexanes and Investigations on Their Retro Diels–Alder Reaction

In this study, two alicyclic dianhydrides, bicyclo[2.2.2]oct-7-ene-2-exo,3-exo,5-exo,6-exo,7-methyltetracarboxylic-2,3:5,6-dianhydride (MBTA) and bicyclo[2.2.2]oct-7-ene-2-exo,3-exo,5-exo,6-exo,7,8-dimethyltetracarboxylic-2,3:5,6-dianhydride (DMBTA), containing methyl substituents on the double-bond bridged cyclohexane structures were successfully synthesized by Diels–Alder reaction. The chemical structures of these dianhydrides with exo-exo configuration were fully characterized by NMR spectroscopy and X-ray single crystal diffraction. Alicyclic polyimides were prepared from these dianhydrides and diamines, such as 4,4′-oxydianiline (4,4′-ODA) and 2,2′-bis(trifluoromethyl)benzidine (TFMB). The introduction of methyl substituents on the double-bond bridges exhibits enhancements in various properties compared with their nonsubstituted analogs. These polyimides with high molecular weights can form flexible, transparent, and colorless films with superior optical transmittance at wavelength 400 nm (T₄₀₀) of 86–88% and yellow indices (b*) of 0.32–0.87. They also showed high thermal stability with the degradation temperature at 5% weight loss (T_d^5%) of 423–447 °C in nitrogen and glass transition temperature (T_g) of 372–417 °C. These polyimides are good candidates as substrates for flexible electronic application. These polyimides also showed excellent solubility in organic solvents. Especially, PI-MBTA/TFMB and PI-DMBTA/TFMB are soluble even in low-boiling-point solvents such as cyclopentanone (CPN), implying the potential application as negative photosensitive polyimides (PSPIs) using CPN as the developing solvent. The double bonds of the bridges of MBTA and DMBTA cannot be hydrogenated with hydrogen pressure of 1–4.5 kg cm^–2 using palladium on carbon as the catalyst at room temperature for 1–5 days. This could be attributed to the steric hindrance of the methyl substituents on the double bond. From the results of model compounds and the addition of strong dienophile (maleic anhydride), we conclude that the double-bond bridged cyclohexane system cannot undergo retro Diels–Alder reaction at 360 °C.

更新日期：2022-12-07

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