We have done a detailed study on the thermal conductivity of aromatic polyimide aerogels. They used 4,4'-diaminodiphenyl ether and 3,3',4,4'-diphthalic dianhydride as the single The polyimide sol is obtained by the sol-gel method, and the polyimide sol is obtained by CO2 supercritical drying to obtain the polyimide aerogel. The thermal conductivity of the obtained samples was tested in N2 and CO2 atmospheres, and it was found that the thermal conductivity was lower in CO2 atmosphere, as shown in Figure 1. And studied the effect of gas temperature and pressure on the thermal conductivity, and found that no matter the temperature or pressure increases, the thermal conductivity of the sample will gradually increase, as shown in Figures 2 and 3.

Figure 1 The change of thermal conductivity under different atmospheres Figure 2 The change of thermal conductivity under different temperatures Figure 3 The change of thermal conductivity under different pressures

We selected a new type of diamine monomer 2,2-bis[4-(4-aminophenyl)phenyl]propane and 4,4'-diaminodiphenyl ether together as the diamine, and 3,3', 4,4'-diphthalic acid dianhydride is used to synthesize polyamic acid solution, and cross-linked polyimide aerogel is obtained by using an amphoteric amino silane as a cross-linking agent. The addition of new monomers makes polyimide Aerogel has a certain degree of hydrophobicity, as shown in Figure 4. At the same time, because the new monomer contains ether bridging part, the solubility of the sample is increased. On the other hand, due to the presence of the methyl group on the side chain, the polarity of the molecule is weakened to a certain extent, which also makes the polyimide The solubility increases, as shown in Figure 5.

Figure 4 Hydrophobic angle test and water absorption performance of polyimide aerogel

Figure 5 Polyimide aerogel is dissolved in NMP