Three series of sulfur-containing polyimides with the bis(3-(trifluoromethyl)phenyl)thiophene moiety were reported. The synthesis of high-refractive-index polyimides was carried out using a nucleophilic substitution reaction. For that, two new sulfur-containing aromatic amino monomers were developed, one bifunctional and one trifunctional. The monomer and polymer structures were successfully characterized by NMR and Fourier transform infrared (FTIR) spectroscopic methods. Free-standing polyimide films of ∼10 μm were prepared, and they were found to have high thermodynamic stability with T_g as high as 257 °C and T_d5% above 500 °C. The films were flexible as well as tough with up to 16 ± 7% elongation at break, with a Young’s modulus of 2.6 ± 5 GPa. Indication for melt processability of one of the polyimides was also demonstrated at a temperature of 30 °C above its T_g. Thin films with thickness in the nanometer range were coated over modified Si-wafers. Increase in the sulfur and aromatic contents in the polymer backbone resulted in the increase of their refractive index; thus, the polymers synthesized in this work exhibited refractive index as high as 1.76 at 589 nm. The transmittance and birefringence of the polyimides were found to improve by modification in the chemical structure. The tuneable optical properties and good dynamic stability of the polyimides make them potential candidates in optoelectronic applications.

中文翻译：

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用于高折射率应用的含双（3-（三氟甲基）苯基）噻吩的富硫聚酰亚胺

报道了三个系列的具有双（3-（三氟甲基）苯基）噻吩部分的含硫聚酰亚胺。使用亲核取代反应进行高折射率聚酰亚胺的合成。为此，开发了两种新的含硫芳族氨基单体，一种是双官能的，一种是三官能的。通过核磁共振和傅里叶变换红外 (FTIR) 光谱方法成功地表征了单体和聚合物结构。制备了约 10 μm 的自支撑聚酰亚胺薄膜，发现它们具有高热力学稳定性，T _g高达 257 °C 和T _d5%500°C 以上。薄膜既柔韧又坚韧，断裂伸长率高达 16 ± 7%，杨氏模量为 2.6 ± 5 GPa。在高于其T _g 30 °C 的温度下，也证明了其中一种聚酰亚胺的熔融加工性能. 厚度在纳米范围内的薄膜被涂覆在改性硅晶片上。聚合物主链中硫和芳烃含量的增加导致它们的折射率增加；因此，在这项工作中合成的聚合物在 589 nm 处表现出高达 1.76 的折射率。发现聚酰亚胺的透射率和双折射通过化学结构的改变得到改善。聚酰亚胺的可调光学性质和良好的动态稳定性使其成为光电应用的潜在候选者。