Cardo基低介电聚酰亚胺的合成及性能

Synthesis and Properties of Low Dielectric Polyimide Containing Cardo Group

以9,9-双(4氨基苯基)芴、对苯二胺、3,3′,4,4′-联苯四羧酸二酐为原料成功制备了一系列含联苯芴(Cardo)基的低介电聚酰亚胺,并表征了其各项性能。通过红外吸收光谱证明了聚酰亚胺的亚胺化程度,X射线衍射(XRD)表征了材料的聚集态结构,材料的分子间距随着Cardo基引入而变大;通过热重分析(TG)和动态热机械分析(DMA)表征了材料的热性能,结果表明,随着分子链中Cardo基含量的增加,玻璃化转变温度从340℃增加到372℃,1%的失重温度从568℃降低到507℃;通过分子模拟表明,大侧基效应导致自由体积增大,分子自由度减弱。介电测试表明,在1 MHz条件下,随着Cardo基含量的增加,介电常数从3.56降低到3.37,介电损耗从0.019降低到0.015。力学性能测试表明,Cardo基引入,材料变脆,拉伸模量和断裂伸长率下降较明显。

The films of low dielectric polyimide were prepared by incorporating 9,9-bis(4-aminophenyl)fluorene(Cardo-NH2)into polymer backbones 3,3′,4,4′-biphenyltetracarboxylic dianhydride(BPDA)/p-phenylenediamine(PDA).The degree of imidization of materials was proved by Fourier transform infrared spectroscopy(FTIR).The aggregate structure of PIs was characterized by X-ray diffraction(XRD),and the d-spacing of the materials became larger with the introduction of Cardo groups.The thermal properties of the materials were characterized by thermogravimetric analyzer(TG)and dynamic mechanical analyzer(DMA).With the increasing of the Cardo group contents in the molecular chain,the glass transition is increased from 340 to 372℃,and the 1%weight loss temperature is decreased from 568 to 507℃.The molecular simulations show that the Cardo group effect leads to an increasing fractional free volume(FFV)between molecular chains and a weakening of the molecular degrees of freedom.The dielectric test shows that the dielectric constant decreases from 3.56 to 3.37 and the dielectric loss decreases from 0.019 to 0.015 with the increase of Cardo group contents at 1 MHz.The mechanical properties tests show that the material becomes brittle due to the introduction of Cardo,and the tensile modulus and elongation at break decrease significantly.