Green and Facile Synthesis of Hybrid Composites with Ultralow Dielectric Properties from Water-Soluble Polyimide and Dual-Porous Silica Nanoparticles

Abstract

Here, we proposed an eco-friendly synthetic method for synthesizing hybrid composites with ultralow dielectric properties at high frequencies up to 28 GHz for true 5G communication from aqueous aromatic polyimide (PI) polymers and dual-porous silica nanoparticles (DPS). The "one-step" water-based emulsion template method was used to synthesize the macroporous silica nanoparticles (MPS). A substantially negative ζ potential was produced along the surface of MPS by the poly(vinylpyrrolidone)-based chemical functionalization, enabling excellent aqueous dispersion stability. The water-soluble poly(amic acid) (PAA), as a precursor to PI, was also "one-step" polymerized in an aqueous solution. The MPS were dispersed in a water-soluble PAA matrix to create the hybrid composite films using an entirely water-based approach. The compatibility between the PAA matrix and MPS was elucidated by investigating relatively diverse end-terminated PAAs (with either amine or carboxyl group). It was also discovered that, during a thermally activated imidization reaction, the MPS are in situ converted into the DPS with macro-and microporous structures (with a surface area of 1522.4 m 2 /g). The thermal, dielectric, mechanical, and morphological characteristics of each composite film were examined, while the amount of DPS in the PI matrix varied from 1 to 20 wt %. With the addition of 5 wt % DPS as an optimum condition, it showed ultralow dielectric properties, with the D k and D f being 1.615 and 0.003 at a frequency of 28 GHz, respectively, and compatible mechanical properties, with the tensile strength and elastic modulus being 78.2 MPa and 0.32 GPa, respectively. These results can comprehensively satisfy various physical properties required as a substrate material for 5G communication devices.

Research Advances of Porous Polyimide—Based Composites with Low Dielectric Constant

“…When the content of SiO 2 hollow spheres reached 5 wt.%, the dielectric constant of the composite film decreased to 2.24 at 1 kHz while improving its thermal stability. Kim et al [ 54 ] employed a “one-step” water-based emulsion template method to synthesize the microporous silica nanospheres (MPS), as displayed in Figure 4 a,b, and dispersed poly(vinylpyrrolidone) functionalized MPS into a PAA solution to create the dual-porous silica nanoparticles (DPS)/PI composite after thermally activated imidization reaction in which the MPS were in situ converted into the DPS with macro- and microporous structures. It was observed from Figure 4 c,d that with the addition of 5 wt.% DPS, the dielectric constant and dielectric loss were 1.62 and 0.003 at 28 GHz, respectively, due to the increase in air voids with the incorporation of DPS.…”

Development of a High‐Frequency Polytetrafluoroethylene (PTFE)‐Based Laminate With An Ultra‐Low Dielectric Constant by Combination of Ceramic Hollow Spheres and PTFE Resin

“…[5] Because the dielectric constant of air is close to 1, raw material resins with good molecular symmetry, and air pores enclosed within the resin can lower the dielectric constant of the composites. [6,7] Porous silica, [8,9] silica oxide hollow powders, [10] and ceramic hollow spheres [11] have been reported as the main inorganic fillers for dielectric composite substrates. The shell of ceramic hollow spheres is a composite material composed of silica and alumina in a specific ratio, which has a remarkable hydrophilic property.…”

Sustainable Dielectric Films with Ultralow Permittivity from Soluble Fluorinated Polyimide

“…These dielectric materials with low dielectric constant can decrease the capacitance between metal interconnects, resistance–capacitance delay, line-to-line crosstalk noise, and power dissipation, which makes them suitable as high-frequency, low-loss boards; semiconductor packaging materials (e.g., chip modules); and interlayer dielectrics (e.g., transistor devices) [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ]. For example, dielectrics in printed circuit boards must have a dielectric constant ( k ) value of <2.5 and a dissipation factor of <0.002 at frequencies greater than 5 GHz in order to meet the criteria of 5G mobile communication in terms of reliability and signal delay [ 9 , 10 , 11 ]. A variety of polymers, including polyimide (PI), polytetrafluoroethylene (PTFE), polystyrene (PS), polypropylene (PP), and polycarbonate (PC), have been extensively investigated as promising candidates for low- k materials.…”