Porous polyimide (PI) thin films have been fabricated successfully by using silica microparticles (MPs) with different particle sizes as a template, and the three dimensional porous structure has been observed clearly by mean of transmission electron microtomography. The measured values of dielectric constant (ε) decreased remarkably by introducing a porous structure, compared with ordinary PI thin films. Especially, the porosity evidently increased (ca. 10%) by suitably employing silica MPs having different particle sizes, and then the value of ε was further reduced. Bruggeman model could reproduce nearly the relationship between the value of ε and porosity.

中文翻译：

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使用两种不同粒径的模板制备的多孔聚酰亚胺薄膜的超低介电性能

以不同粒径的二氧化硅微粒（MPs）为模板，成功制备了多孔聚酰亚胺（PI）薄膜，并通过透射电子显微照相清晰地观察到三维多孔结构。与普通的PI薄膜相比，通过引入多孔结构，介电常数（ε）的测量值显着降低。特别地，通过适当地使用具有不同粒径的二氧化硅MP ，孔隙率明显增加（约10％），然后ε值进一步降低。Bruggeman模型几乎可以重现ε值与孔隙率之间的关系。