Vibrational Spectroscopic Analysis of Water Absorption in Polyimides and the Correlation with Dielectric Properties at 10 GHz

作者：Ririka Sawada, Haonan Liu, Shinji Ando · 发表于：The Journal of Physical Chemistry B · 年份：2025 · DOI：10.1021/acs.jpcb.5c05709 · 被引用次数：11 · 研究领域：Synthesis and properties of polymers、Dielectric materials and actuators、Epoxy Resin Curing Processes

High Resolution Image Download MS PowerPoint Slide Unveiling the mechanism behind the relative humidity (RH) dependence of the dielectric properties of polyimides (PIs) in the high-frequency (GHz) range is a crucial challenge in the development of novel low-dielectric thermally stable polymers. Herein, the correlations among the dielectric constant ( D k ), dissipation factor ( D f ), water absorption content, and hydrogen-bonding structures of sorbed H 2 O molecules were precisely analyzed for 15 types of aromatic and semiaromatic PIs based on variable-RH Fourier transform infrared (FT-IR) vibrational spectroscopy. The absorbance of the IR bands assignable to the O–H stretching (ν(OH)) and H–O–H bending (δ(HOH)) vibrations of H 2 O molecules sorbed in PI films gradually increased with an increase in the RH of the atmosphere. Notably, the slopes of the increase in D k and D f against the integrated area of the δ(HOH) IR band ( A δ(HOH) ), which can be used as a measure of the concentration of sorbed H 2 O, were nearly constant and independent of the chemical structure of PIs. However, the slopes of the RH dependences of D k and D f, that is, h Dk and h Df, were strongly dependent on the structure of PIs and proportional to each other. This confirms that the amount of water absorbed is a crucial factor in the RH dependence of D k and D f . The D k values of the PIs increased linearly with an increase in A δ(HOH), whereas the D f values increased linearly with A δ(HOH) at a low...