Temperature-Invariant Large Broadband Polyimide Dielectrics with Multimodal Porous Networks

Abstract

Herein, we describe sponge-like polymeric materials with multimodal porous networks with stable ultralow dielectric properties over broad frequency and temperature ranges. A hierarchically porous polyimide (PI) film was prepared via nonsolventinduced phase separation (NIPS), followed by stepwise thermal imidization. Through the swelling and the subsequent liquid−liquid phase separation, highly insulating interconnected pores of the internal layer and the water-vapor impermeable, closed-cell skin of the outer layer were directly formed on the PI film. The grafting of porous PI onto amino-functionalized mesoporous silica (AMS) to further adjust the overall thermal stability and dielectric constant has become a valid strategy. The porous PI-grafted-AMS (PPI-g-AMS) exhibited uniform micropores, which were regularly shaped with an average diameter of 16.3 ± 0.6 μm. The glass transition temperature (T g ) of PPI-g-AMS increased considerably from 367 °C to as high as 398 °C because of the formation of interchain cross-linking bridges in the AMS. Outstanding dielectric constant (D k ) and dissipation factor (D f ) of 1.84 and 0.0018 at a frequency of 1 MHz, respectively, were achieved for PPI-g-AMS-1 with the addition of AMS with 1% wt. Moreover, stable and ultralow D k (∼1.84 at 1 MHz) and D f (∼0.001 at 1 MHz) values were achieved over a broad temperature range from −20 to 200 °C. These findings indicate the broad application potential of polymeric materials as interlevel insulation materials in the next-generation 5G/ 6G infrastructure.

Frequency-Dependent Dielectric Permittivity and Water Permeability in Ordered Mesoporous Silica-Grafted Fluorinated Polyimides

“…However, the original honeycomb-patterned mesoporous scaffold was not destroyed during the post-grafting amination. Thermogravimetric weight loss curves for MS and AMS are shown in Figure 1 d. The TGA curve of the AMS exhibits three weight loss intervals that are distinct from MS: (i) desorption of the water linked to the silica surface in the range of 50–150 °C, (ii) fragmentation of the organic functionalities attached to the AMS surface in the range of 200–600 °C, and (iii) mesoporous structure disruption above 600 °C [ 24 , 30 ].…”

“…Mesoporous silica, such as polyhedral oligomeric silsesquioxanes, Santa Barbara Amorphous-15, or Mobil Composition of Matter No. 41 (MCM-41), has emerged as a research hotspot for reducing D k and improving other properties [ 22 , 23 , 24 ]. Among them, MCM-41 exhibits an intrinsically low D k of 1.4–2.1 due to its regular arrangement of cylindrical mesopores (3–4 nm) that form a one-dimensional pore system.…”

Versatile Landscape of Low-k Polyimide: Theories, Synthesis, Synergistic Properties, and Industrial Integration

“…The porous structure can be formed by selectively removing one of the phases by separating it as a gas or liquid when the temperature or other external conditions are changed. With the continuous research and exploration in recent years, the family of phase separation mainly has expanded to water vapor induced phase separation (WVIPS), , nonsolvent induced phase separation (NIPS), − and thermally induced phase separation (TIPS) …”

Graft Architectured Poly(phenylene oxide)-Based Flexible Films with Superior Dielectric Properties for High-Frequency Communication Above 100 GHz

“…Up to now, various polymers including modified polyimide (mPI) and liquid crystal polymer (LCP) have been widely studied as polymeric substrates and dielectric layers for FCCL. − Despite significant progress being made on this front, achieving the aforementioned prerequisite properties still remains a major challenge. In detail, mPI, which has been widely used as electrical insulation layers, has high D f at high-frequency regimes and water uptake, limiting its usage in high-frequency applications. − While LCP demonstrates the potential for exceptional dielectric properties for FCCL in high-frequency regimes and reduced water absorption, the LCP film produced using traditional processing methods inherently showed anisotropic mechanical properties . Furthermore, the cost efficiency of LCP presents a hindrance to their widespread application. − Given these, developing new dielectric polymeric layers presenting low D k , low D f , thermal/mechanical stability, and low water uptake is an interesting issue.…”