Mechanically strong, thermal-insulated, and ultralow dielectric polyimide aerogels with adjustable crosslinking methods

Abstract

Polyimide (PI) aerogels can exhibit controllable physical and chemical properties by changing the type of dianhydride and diamine monomers. However, few works aim to reveal the effects of monomer hybridization and crosslinking methods on the properties of polyimide aerogels. In this work, we studied the effects of single and double crosslinking methods on the density, microstructure and properties of PI aerogels. The results showed that different crosslinking methods could cause completely opposite variation trends of shrinkage and density. The single crosslinking PI aerogels possess large shrinkage of 23.8% and high thermal conductivity of 59.9 mW/(m·K). However, with the same formula, the PI aerogels prepared by the double crosslinking method possess smaller shrinkage of 12.3% and lower thermal conductivity of 28.7 mW/(m·K). The dielectric constant of the double crosslinking PI aerogels shows a lower dielectric constant of 1.10 compared to the single crosslinking PI aerogel of 1.34 when containing the same content of 6FDA. The addition of 6FDA can also increase the 5% thermal decomposition temperature of PI aerogels from 445.5 °C to 460 °C. The as-prepared double-crosslinking PI aerogels present superior properties of lightweight, low dielectric constant and dielectric loss, low thermal conductivity and high temperature resistance, which provides a new way for adjusting the performance of PI aerogels. • PI aerogels prepared by the double crosslinking method possess low shrinkage (12.3%) and thermal conductivity (28.7mW/(m·K)). • The dielectric constant of double crosslinking PI aerogels shows low dielectric constant of 1.10. • The addition of 6FDA can also increase the 5% thermal decomposition temperature of PI aerogels from 445.5 °C to 460 °C.