Synthesis and Characterization of a Colorless Polyimide Membrane with Low Dielectric Constant

Abstract

Recently, colorless polyimide (CPI) substrates with excellent optical properties, suitable thermal stability, and low dielectric constant have become a key factor in the development of wearable and portable flexible electronic devices. In this paper, a series of branched CPI films are successfully prepared using self-made triamine. By adjusting the ratio of two types of dianhydride monomers, CBPI-10 film achieves the highest transmittance (90% at 550 nm) and the highest glass transition temperature (311 °C). The reason for this result is that CBPI-10 contains the least amount of trifluoromethyl side groups and the most alicyclic units, resulting in the generation of the minimum free volume fraction (according to molecular dynamics simulations) and the disruption of the conjugation effect between the benzene rings. Additionally, it is worth mentioning that the highest dielectric constant of these films is only 2.17. Consequently, this study focuses on providing a novel manufacturing scheme for branched CPIs, which has guiding significance for the design of colorless polymers and the advancement of flexible display technology.

Keywords: Colorless polyimide, Transparent polyimide, Branched, Dielectric constant, Flexible electronic devices