Polymer Concentration and Liquid—Liquid Demixing Time Correlation with Porous Structure of Low Dielectric Polyimide in Diffusion-Driven Phase Separation

Abstract

Porous polyimide (PI) films are a promising low-k dielectric material for high-frequency data transmission with low signal attenuation. Pores are generated by non-solvent induced phase separation (NIPS) during phase inversion of polymer solution via non-solvent accumulation and solvent diffusion. In this study, aromatic PI was employed as a matrix for NIPS, and the influence of polymer concentration and liquid—liquid demixing time on the morphology of pores in the PI films was investigated. This ensured control over the porous structure of the PI film and provided desirable dielectric properties in a broad frequency range of 100 Hz–30 MHz (1.99 at 30 MHz) and thermal stability (Td5% > 576 °C, Tg > 391 °C). This study addresses the effect of polymer concentration and coagulation time on the morphology and physical properties of PI sponge films and provides guidance on the design and optimization of architectures for polymeric materials requiring pore modification.

Carbon nitride/polyimide porous film via an NIPS method with advanced dielectric and hydrophobicity properties

“…Porous polymer lms have been prepared by various methods, such as the use of foaming agents, the pyrolysis foaming method, chemical dissolution of block domains of the copolymer, and the non-solvent induced phase separation (NIPS) method. [23][24][25][26] As a exible method, NIPS has been commonly utilized to fabricate various porous polymer lms. Khim et al 27 fabricated a hierarchically porous PI lm by NIPS and graed PI onto amino-functionalized mesoporous silica (AMS) to further regulate the thermal stability and dielectric constant (3 0 = 1.84).…”

In situ fabrication of Fe3C nanoparticles and porous-carbon composites as high-performance electromagnetic wave absorber

“…As previously reported, the selection of polyimide (PI) as the carbon precursor stems from its outstanding thermal stability and amendable characteristics for modication. [29][30][31] In our previous work, we demonstrated that PI-derived porous carbon prepared via LLPS maintains its porous structure during pyrolysis and revealed that increasing carbonization temperature impacts EMW absorption performance. 32 Herein, to further explore the conformational relationship between the types, contents, and morphology of nanoparticles and their EMW absorption performance, we varied iron acetylacetonate and acetylacetone cobalt(III) as the magnetic nanoparticles source, incorporating it into a polyamic acid solution through rapid stirring to form the composite material precursor.…”

Temperature-Invariant Large Broadband Polyimide Dielectrics with Multimodal Porous Networks

“…The Maxwell–Garnett model indicates that the porous structure in PI films can substantially reduce the dielectric permittivity since the D k of air ( k ≈ 1) is constant. , Porous PIs have been prepared using various methods, such as the use of blowing agents, the decomposition of a thermally labile domain in a phase-separated block or graft copolymer, and the inclusion of porous/hollow ceramic components − or porogens. − Although such methods require additives to create pores in the polymer matrix, thermodynamic phase separation allows the spontaneous formation of asymmetric porous structures in polymer matrix. Nonsolvent-induced phase separation (NIPS) is a method of fabricating a porous polymer film by immersing a homogeneous polymer solution in a poor solvent using the principle of phase separation. , At the beginning of the NIPS method, rapid phase separation can occur at the contact interface between the polymer solution and nonsolvent, resulting in a thin dense layer at the contact surface. , This layer can inhibit large water vapor permeation that deteriorates dielectric properties. An increase in porosity decreases the dielectric constant but tends to deteriorate the thermal and physical properties of the porous polymer. , Caution needs to be exercised regarding the morphological architecture and molecular network of PI to solve the difficulty in developing reliable ultralow-k dielectrics with multiple target properties.…”

“…28,29 At the beginning of the NIPS method, rapid phase separation can occur at the contact interface between the polymer solution and nonsolvent, resulting in a thin dense layer at the contact surface. 30,31 This layer can inhibit large water vapor permeation that deteriorates dielectric properties. An increase in porosity decreases the dielectric constant but tends to deteriorate the thermal and physical properties of the porous polymer.…”