Department of Polymer Engineering , University of Akron , Akron , Ohio 44325 , United States.
NASA Glenn Research Center , 21000 Brookpark Road , Cleveland , Ohio 44135 , United States.
ACS Appl Mater Interfaces. 2019 Mar 6;11(9):9425-9437. doi: 10.1021/acsami.8b20420. Epub 2019 Feb 22.
Polyimide aerogels are mechanically strong porous solids with high surface area, low density, and dielectric constants close to 1, making them ideal materials for use as substrates for lightweight antennas. Increasing the flexibility of the polyimide aerogels extends the usefulness for conformal antennas for use on small aircraft such as unmanned air vehicles or personal air mobility vehicles. To this end, polyimide aerogels made with aromatic amines with 4-10 methylene units as flexible spacers between aromatic rings in the backbone have been fabricated. Substituting 25-75 mol % of fully aromatic 2,2'-dimethylbenzidine with these flexible diamines increases the flexibility of polyimide aerogels, making them bendable at thicknesses up to 2-3 mm. The density, dielectric constants, thermal and moisture stability, and mechanical properties of these aerogels were assessed to understand the effect of the amount and length of the methylene spacers on these properties.
聚酰亚胺气凝胶是机械强度高的多孔固体，具有高比表面积、低密度和介电常数接近 1，使其成为用作轻质天线基板的理想材料。增加聚酰亚胺气凝胶的柔韧性可扩展用于小型飞机（如无人机或个人空中机动车辆）上的共形天线。为此，已经制造了用具有 4-10 个亚甲基单元的芳族胺制成的聚酰亚胺气凝胶，作为主链中环芳族之间的柔性间隔物。用这些柔性二胺取代 25-75 mol%的全芳族 2,2'-二甲基联苯，可增加聚酰亚胺气凝胶的柔韧性，使它们在厚度高达 2-3 毫米时可弯曲。评估了这些气凝胶的密度、介电常数、热和湿度稳定性以及机械性能，以了解亚甲基间隔物的数量和长度对这些性质的影响。
