The increasing demand for high-frequency communication systems has intensified the need for polymeric dielectrics combining low dielectric constants (Dk) and loss (Df) to minimize the signal attenuation, signal loss, and cross-talk, while robust mechanical and thermal stabilities are required to secure performance reliability. Herein, we propose the synthesis of low dielectric cross-linked polyimide by inducing the formation of free volume during the polymerization of bismaleimide-terminated oligoimides. To study the dependence in the formation of free volume in the polymer matrix, maleimide-terminated oligoimide precursors with controlled oligomer molar mass (Mn= 4.1-10.4 kg mol-1) were synthesized. The cross-linked networks were fabricated through thermal radical polymerization, optionally copolymerized with styrene for further regulation in microstructures. The decrease in film density of the resulting cross-linked film was observed, while the more amorphous inter-chain packing structure was confirmed by wide-angle X-ray scattering (WAXS). These structural modification effectively reduces the dipole density in the polymer matrix, achieving Dk = 2.78, Df = 0.0042 @28 GHz, compared with the corresponding linear polyimide (Dk = 3.04, Df = 0.0090 @28 GHz). The resulting cross-linked networks retained their thermal stability (Td,5% = 457-480 degrees C, T alpha = 199-216 degrees C) and enhanced mechanical integrity (E = 2.28-2.74 GPa) compared to linear PI with identical chemical structure. These results suggest that the material design utilizing the cross-linking chemistry enables to achieve the control over free volume and structural rigidity, providing a synthetic strategy for high-performance dielectric materials for next-generation high-frequency applications.

Redistribution layers (RDLs) are key structural components in advanced semiconductor packaging, where materials must combine low dielectric constant (D-k), photopatternability, and PFAS-free composition under low-temperature processing conditions. Conventional photosensitive polyimides (PSPIs), however, generally require thermal imidization above 350 degrees C and exhibit D-k above 3.0, limiting their integration with fine-pitch RDL architectures. Herein, we report a series of designed soluble PSPIs synthesized from hydroxyl-containing diamines-3,3,3 ',3 '-Tetramethyl-1,1 '-spirobisindane-5,5 '-diamino-6,6 '-diol (DHSBI), 9,9 '-Bis(4-aminophenyl)-9H-fluorene-2,7-diol (APFD), and 2-Amino-4-[1-(3-amino-4-hydroxyphenyl)cyclohexyl]phenol (AACP)-modified with methyl methacrylate (MMA) groups to introduce both photoreactivity and dielectric tunability. The incorporation of bulky, low-polarity MMA-functionalized diamines increases free volume and reduces chain packing, leading to significantly lower permittivity (D-k = 2.67 @ 40 GHz) while enabling direct UV patterning without additional thermal imidization. These PSPIs exhibit excellent pattern fidelity down to 20 mu m, strong Cu adhesion, and a low curing temperature of 250 degrees C. The rational design of MMA-grafted diamine monomers demonstrates a viable route to low-D-k, photocurable, and environmentally sustainable PI systems for next-generation high-density semiconductor packaging.

Fluorene-containing polyimides with pendant hydroxyl groups were synthesized via azeotropic imidization from BPADA, mTB, and APFD in varying feed ratios. Post-polymerization cross-linking with terephthaloyl chloride (TPC) generates covalent junctions between polymer chains, disrupting dense packing and arresting expanded inter-chain free space. Wide-angle X-ray Scattering (WAXS) analysis confirmed that the formation of cross-linked networks increased free volume in the polymer matrix, leading to a reduction in dielectric constant (Dk) and dissipation factor (Df). The CBMAD73(1.0) film exhibited the advanced low dielectric properties with Dk = 2.66 and Df = 0.0056 at 10 GHz, compared to 3.13 and 0.0246 at 10 GHz for the polymeric precursor, BMAD73. Thermal analysis demonstrated that the cross-linked polymer network retained thermal stability, which is comparable to that of the neat polyimide precursor, demonstrating structural integrity of the cross-linked network. These results highlight post-polymerization cross-linking as an effective approach for modulating nanoscale free volume to achieve low dielectric performances while maintaining thermal stability required for high-frequency electronic applications.

Due to the development of communication technology, a low dielectric film for application to the industry is required. In order to study the formation and properties of inclusion complexes using representative polyimide exhibiting such low dielectric properties and cyclodextrin (CD) as a ring component, through mixing diamine used as a monomer for polyimide, polyamic acid as a polymerization precursor, and polyimide was attempted. In order to research the formation and properties of inclusion complex using CD as ring components, an inclusion complex was formed by mixing diamine used as a monomer for polyimide, polyamic acid as a polymerization precursor, and polyimide. Through FTIR spectrum analysis of the solution obtained by mixing each component and CD and dissolving it in dimethyl sulfoxide (DMSO), it was possible to confirm the wide band of 3100 to 3600 cm(-1) due to the presence of many hydroxyl groups (-OH) in CD, and the stretchable vibration band of CD specific C-O-C and C-O around 1150 cm(-1). In addition, using H-1 NMR spectrum analysis, the inclusion complex formation could be confirmed by the chemical shift of CD in all solutions.

A critical challenge in flexible high-performance thin-film transistors (TFTs) is ensuring the reliability of the dielectric layer with a high-mobility semiconductor, which must maintain its insulating properties while withstanding repeated mechanical deformation. In this study, we investigate photo-cross-linkable photosensitive polyimide (PSPI), 4,4'-(hexafluoroisopropylidene)diphthalic anhydride-3,5-diaminobenzyl cinnamate (6FDA/DABC), as a dielectric material in oxide TFTs using zinc tin oxide or indium gallium zinc oxide as the channel materials. The photo-cross-linked PSPI dielectric exhibited a high areal capacitance of 17.5 nF cm-2 at 1 kHz, an ultralow leakage current density of 10-10 A cm-2 at 2 MV cm-1, and a breakdown field exceeding 6.7 MV cm-1 under static conditions. Under repeated mechanical stress, the dielectric maintained its low leakage current and structural integrity after 10,000 bending cycles, ensuring a stable electrical performance. The photo-cross-linked PSPI and zinc tin oxide-based TFT device demonstrated excellent electrical characteristics, achieving a high mobility of 15.5 cm2 V-1·s-1, an on/off current ratio of 1.5 × 109, and good electrical stability under positive and negative bias stress, confirming its potential for high-performance, flexible TFT applications.

MXene-based composites are widely recognized for their exceptional electromagnetic interference (EMI) shielding capabilities. While incorporating porous structures can enhance shielding efficiency, achieving scalable and uniformly distributed porosity remains a significant challenge. Here, we report the fabrication of large-area, flexible, and porous MXene/polyimide (PI) composite films using a water-borne polyimide (W-PI) matrix and polycarboxylate ether (PCE)-functionalized Ti3C2Tx MXene. The comb-like structure of PCE ensures uniform MXene dispersion, while its branched functional groups promote the formation of macro pores during thermal imidization. As a result, the composites exhibit outstanding EMI shielding effectiveness, reaching 66.1 dB in the X-band and 85.0 dB in the Ka-band. The porous architecture, generated through PCE evaporation and MXene thermal expansion, enhances both reflection and absorption pathways, further improving shielding performance. Additionally, the films demonstrate high electrical conductivity, exceptional flexibility with bending radii below 2 mm, and remarkable durability, retaining over 95 % of their shielding efficiency after 1000 bending cycles. This eco-friendly, water-borne processing strategy, combined with scalable slot-die coating, highlights the immense potential of these composites for next-generation applications in 5G communications, wearable electronics, and flexible devices.

The water-borne aromatic poly(amic acid) salt (W-PAASs) is gaining attention as an eco-friendly approach to synthesizing precursors for high-performance polyimide (PI) materials. However, widening the versatility of the chemical structure in aromatic monomers for tuning the novel physical properties of the resulting polymers remains challenging. In this study, we introduce a surfactant-assisted, one-pot synthesis of W-PAASs, an efficient approach to broadening the chemical diversity of water-borne PI precursors. The surfactant effectively increases the interface of hydrophobic monomers with the aqueous medium, accelerating the reaction between the dianhydride and diamine monomers. This enables the use of hydrophobic monomers such as 4,4-oxidianline, 1,3-bis(4-aminophenoxy)-benzene, and 4,4-diaminophenyl sulfide. The chemical versatility of synthetic monomers allows for the preparation of PI films with novel mechanical, thermal, and optical properties. Our findings demonstrate that improving the synthetic environment for W-PAAS is crucial for developing advanced engineering plastics through sustainable, eco-friendly processes, paving the route for future high-tech applications.

Wireless powering of implantable medical devices (IMDs) using triboelectric nanogenerators (TENGs) has gained attention as a sustainable and battery-free energy strategy. Ultrasound-driven TENGs (US-TENGs) offer favorable biocompatibility and deep tissue accessibility, but their practical application remains limited by unstable acoustic vibration, filler aggregation at low contents, and complex electrode integration. Here, we report a porous polyimide composite-based TENG (PPC-TENG) designed to overcome these limitations through material and structural innovations. The triboelectric layer is fabricated via a Pickering emulsion templating approach using a water-borne poly(amic acid) salt (W-PAAS) and high-permittivity CaCu3Ti4O12 (CCTO) nanoparticles, enabling homogeneous dispersion up to 10 wt % without aggregation. The resulting porous architecture concentrates mechanical deformation at branch-like pore supports, promoting uniform vibration and enhancing charge generation under acoustic actuation. A laser-induced graphene (LIG) electrode is directly patterned on the porous surface, enabling a double-electrode configuration through a simplified, metal-free process. The PPC-TENG exhibits high electrical output, stable capacitor and battery charging performance, and confirmed biocompatibility in both in vitro and in vivo tests. This work presents a scalable and structurally adaptive triboelectric platform for wirelessly powered biomedical electronics.

Thin-film transistors offer excellent and uniform electrical properties over large areas, making them a promising option for various future electronic devices. Polyimide dielectrics are already widely used in various electronic devices because of their exceptional dielectric properties, thermal stability, and desirable mechanical flexibility, which make them suitable for harsh environments. However, the current research on polyimide dielectric materials has certain limitations, such as the use of toxic solvents, high-temperature processes, and deficient coating properties. Herein, we introduce an aromatic polyimide dielectric, which exhibits excellent electrical properties even when processed at a low temperature of 250 degrees C using environmentally friendly water-based "one-step" polymerization. Despite its thin thickness of <200 nm, the water-borne fluorinated polyimide dielectric material demonstrates stable insulating properties over a wide range of electric fields and achieves a high breakdown voltage of over 4.5 MV cm-1. Furthermore, we successfully achieved a large-area coating of uniform dielectric layers with no pinholes using only water as a solvent and a simple solution process without any additional processing steps. These results demonstrate that the water-borne polyimide gated indium-gallium-zinc oxide transistor exhibits excellent and stable device performance. Moreover, we used the transistor to successfully demonstrate various logic gates (NOT, NAND, and NOR). Overall, this study provides guidelines for the eco-friendly and sustainable use of water-borne polyimide dielectric materials with high electrical performance and large-processing window advantages.

The development of water-borne poly(amic acid) salts (W-PAAS) for aromatic polyimide (PI) synthesis represents a significant advancement, offering a straightforward and environmentally friendly process. This study provides an in-depth investigation into the intricate reaction mechanisms of W-PAAS polymerization in an aqueous medium facilitated by an organic base. The polymerization primarily occurs at the interface of dianhydride particles with water, highlighting the critical role of this interface in the reaction. The presence of the organic base lowers the energy barrier, enabling the formation of high-molecular-weight polymer chains. The resulting PI films derived from W-PAAS aqueous solutions exhibit properties comparable to those of traditional organic-solvent-based and commercial PI films. Additionally, the W-PAAS solution can be easily transformed into a hydrogel, highlighting its potential for three-dimensional (3D) structuring applications. This research introduces a novel platform for rational molecular design within aqueous synthetic systems, broadening the scope of high-performance material applications while promoting environmental sustainability.

Alkali-free aluminoborosilicate glasses without (GDMC-Si) and with La2O3 addition (GDMC-La) were fabricated with an aim to develop low dielectric glass fibers for use in printed circuit boards (PCBs) as a reinforcing material in high-speed 5G/6G telecommunications application. This study presents the structural, thermo-physical, and dielectric properties of the glasses. The decrease in glass transition temperature (Tg) and the increase in coefficient of thermal expansion (CTE) were found by the addition of SiO2 and La2O3 in the present glass system, which are due to the depolymerization of the glass networks confirmed by the FTIR analysis. The dielectric constants (Dk) and the dissipation factors (Df) of the glasses were investigated at a high frequency of 10 GHz. The Dk values of the GDMC-Si and GDMC-La glass systems reached a minimum of 4.50 and 4.75, while their Df values reached a minimum of 2.86 × 10-3 and 3.01 × 10-3, respectively. Notably, the Dk and Df values of the present glasses were lower than the commercial E-glass (Dk: 6.9, Df: 7.0 × 10-3 at 10 GHz) and L-glass (Dk: 4.8, Df: 3.0 × 10-3 at 10 GHz). Glass fibers with a diameter of 10 μm were successfully drawn by the continuous melt-spinning process and their mechanical properties were investigated.

This study presents a novel approach that enables an environmentally benign water -based co -solvent synthesis of fluorinated polyimides (FPIs) using conventional fluorine -based monomers such as 4,4 ' -(hexa- fluoroisopropylidene)diphthalic anhydride (6FDA) and 2,2 ' -bis(trifluoromethyl)benzidine (TFMB). The high surface tension inherent in fluorine -based materials, which inhibits water solubility, can be overcome by mixing water with an alcohol -based solvent. The surface tension of the co -solvent decreases proportionally with the alcohol content, facilitating synthesis from fluorine -based monomers that were previously inaccessible in water. Oligomeric fluorinated poly(amic acid) salt (FPAAS) can be rapidly synthesized in aqueous solutions containing alcohol, particularly 1-propanol (PrOH). Subsequent coating and thermal treatment processes allow high molecular weight FPI films to be produced by solid-state polymerization. A comprehensive analysis of the resulting FPI films shows excellent physical properties comparable to conventionally synthesized FPI films. The 6FDATFMB-based FPI exhibits remarkable thermal stability up to 570 degrees C (T d,5% ), low yellow index of 1.37, high transparency of 92.9 % and tensile strength of 116.5 MPa. The presented synthetic strategy allows the adoption of monomers with different fluorine -based substituents, thus providing insights for future aqueous synthesis. The thermal, mechanical, and optical qualities of FPIs can be utilized to create optically clear heating devices. The transparent heater, fabricated on the FPI film utilizing a laser patterning technique to create electrodes from silver nanowires, was capable of increasing the temperature up to 100 degrees C under a 9 V voltage application.

Macroporous polymers have gained significant attention due to their unique mass transport and size-selective properties. In this study, we focused on Polyimide (PI), a high-performance polymer, as an ideal candidate for macroporous structures. Despite various attempts to create macroporous PI (Macro PI) using emulsion templates, challenges remained, including limited chemical diversity and poor control over pore size and porosity. To address these issues, we systematically investigated the role of poly(amic acid) salt (PAAS) polymers as macrosurfactants and matrices. By designing 12 different PAAS polymers with diverse chemical structures, we achieved stable high internal phase emulsions (HIPEs) with >80 vol % internal volume. The resulting Macro PIs exhibited exceptional porosity (>99 vol %) after thermal imidization. We explored the structure-property relationships of these Macro PIs, emphasizing the importance of controlling pore size distribution. Furthermore, our study demonstrated the utility of these Macro PIs as separators in Li-metal batteries, providing stable charging-discharging cycles. Our findings not only enhance the understanding of emulsion-based macroporous polymers but also pave the way for their applications in advanced energy storage systems and beyond.

We have prepared a low-temperature cross-linked soluble polyimide (SPI) as a dielectric material for organic thin-film transistors (OTFTs) to improve their electrical stability. Two types of SPIs (DOCDA/6FHAB and 6FDA/6FHAB) were synthesized by a one-step polymerization process using 5-(2,5-dioxytetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride (DOCDA) and hexafluoroisopropylidene diphthalic anhydride (6FDA) as the dianhydrides and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (6FHAB) as a diamine. To further enhance the electrical performance, the SPI thin films were crosslinked with methylated/ethylated (hydroxymethyl)benzoguanamine (HMBG) through a low temperature process at 160 degrees C. Crosslinking considerably improved the insulating properties, resulting in a substantial reduction in leakage current from 10-7 A cm-2 to 10-9 A cm-2 at 2.0 MV cm-1. When crosslinked SPIs were used as gate dielectrics in OTFTs, device stability and reliability, as measured by the off-current, threshold voltage, and hysteresis, improved significantly. Our results demonstrate the potential of crosslinked SPIs as effective gate dielectric materials for advanced organic thin-film transistors.

The emergence of transition metal carbides and nitrides (MXenes) addresses the rising demand for emerging yet favorable multifunctional materials for their utilization in flexible miniaturized electronics and beyond. However, MXenes pose a significant challenge due to their weak interfacial interactions, which result in inferior mechanical properties and structural integrity in MXene films. The continuous interfacial bridging approach involves incorporating hydrogen, ionic, and covalent bondings, and was developed to fabricate ultrastrong hydroxylated carbon nanotubes (HCNT) intercalated Ti3C2Tx MXene (MX) films (MX@HCNT) with superior mechanical properties, electromagnetic interference (EMI) shielding performance, and thermal conductivity. The MX@HCNT films with hydrogen bonding between MX and HCNT were fabricated by vacuum filtration method and were further crosslinked by a conductive Fe3+ ion (ionic bonding) and glutaraldehyde (GA, covalent bonding) molecules (MX@HCNT/Fe3+/GA). As a result, the continuous interfacial bridging approach facilitates the densification of MX nanosheets in the MX@HCNT/Fe3+/GA films. The resultant densified MX@HCNT/Fe3+/GA films with 50 wt

Evaluation of the insulating properties of polymers, such as the dielectric constant and dissipation factor, is crucial in electronic devices, including field-effect transistors and wireless communication applications. This study applies density functional theory (DFT) to predict the dielectric constant of soluble polyimides (SPIs). Various SPIs containing trifluoromethyl groups in the backbone with different pendant types, numbers, and symmetries are successfully synthesized, and their dielectric constants are evaluated and compared with the DFT-estimated values. Two types of DFT-optimized SPIs, single-chain and stacked-chain models, are used to describe the local geometries of the SPIs. In addition, to reveal the relationship between the molecular structure and dielectric constant, further investigations are conducted by considering the dielectric constant of composing ionic and electronic components. The DFT-estimated static dielectric constant of the single-chain model accurately reproduces the corresponding experimental value with at least 80% accuracy. Our approach provides a rational and accelerated strategy to evaluate polymer insulators for electronic devices based on cost-effective DFT calculations.

Abstract Here, the utilization of a highly uniform water‐borne polyimide (W‐PI) thin film as a gate dielectric layer for large‐scale organic thin film transistors (OTFTs) exceeding 100 cm2 is presented, employing the bar‐coating technique. The W‐PI thin films are obtained uniformly over a large area by systematically manipulating the surface tension of the water‐soluble poly(amic acid) salts (W‐PAAS) solution using alcohol as a co‐solvent in a “Green” process. The thickness of the W‐PI thin film is precisely controlled within the range of tens to hundreds of nanometers by adjusting key parameters, including the concentration of the W‐PAAS solution, wire diameter, and bar‐coating speed. As a result, 500 pentacene‐based OTFTs are successfully fabricated on a 10 × 10 cm2 substrate, utilizing a 280 nm thick W‐PI gate dielectric film. These devices exhibit excellent uniformity, with field‐effect mobility of 0.20 ± 0.02 cm2 V−1 s−1. Furthermore, the fabrication of electronic devices using an environmental‐friendly bar‐coating method on large‐area flexible substrates is demonstrated. This study highlights the considerable potential of eco‐friendly W‐PI thin films as dielectric materials, offering advantages such as cost‐effectiveness and high efficiency for reliable industrial applications.

A solution-processable and photocurable polyurea (PU) with excellent electrical and dielectric properties is synthesized, characterized, and applied as a gate dielectric in high-performance organic thin-film transistors (OTFTs). The PU is synthesized from toluene-2,4-diisocyanate and 3,5-diaminobenzyl cinnamate via a conden-sation reaction. The PU containing cinnamoyl groups is photo-crosslinked without a photoinitiator and easily micropatterned by selective ultra-violet (UV) exposure. The photo-crosslinked PU (c-PU) film improves dielectric properties and thermal and chemical resistance compared with pristine PU films. We fabricated dinaphtho[2,3-b:2 ',3 '-f]thieno[3,2-b]thiophene (DNTT)-based OTFTs with a c-PU gate dielectric layer to investigate the per-formance of the c-PU thin film as a gate dielectric. The field-effect mobility and on/off ratio of DNTT-based OTFTs with surface-treated c-PU gate dielectric are 0.75 +/- 0.03 cm(2) V(-1 )s(-1 )and 1.60 x 10(6,) respectively. In addition, solution-processed diketopyrrolopyrrole-thienothiophene copolymer-based OTFTs with c-PU gate dielectric show field-effect mobility of 0.07 +/- 0.01 cm(2 )V(-1 )s(- 1) and on/off ratio of 2.88 x 10(5). Furthermore, the complementary inverter was successfully demonstrated by using c-PU with excellent insulating property as the gate dielectric.

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 m2/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 Dk and Df 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.

A water-borne photo-sensitive poly(amic acid) salt for the micropatterned polyimide layer of a microelectronic device.