Dielectric Constant Polyimide Research Articles

Effect of Water Absorption on Electric Properties of Temperature-Resistant Polymers.

The effects of water absorption on the electric resistivity and dielectric constant of polyimide (PI) and poly(ethylene terephthalate) (PET) were investigated, and the mechanism of deterioration in electrical insulation properties was discussed. The polyimides are poly(oxydianiline pyromellitimide) (PMDA-ODA) and poly(para-phenylene diamine biphenyltetracarboxydiimide) (BPDA-PDA). These polymer films were immersed in pure water for various immersion times at room temperature, and the water absorption ratio was evaluated. The electric resistance for these films was measured at room temperature using a high-resistance meter, and the dielectric constant at room temperature was measured using an LCR meter in a frequency range of 200 kHz to 2 MHz. The absorption ratios at equilibrium absorption for PMDA-ODA, BPDA-PDA, and PET were 2.7, 2.5, and 0.5%, respectively. The critical volume fraction of the percolation threshold of electric conductivity due to water absorption was 0.034 for both PMDA-ODA and BPDA-PDA. On the other hand, PET did not show a significant decrease in the resistivity. For both PIs and PET, the dielectric constant observed could be explained by a series model of the respective capacitances of pure water and polymer. Actually, the resistivity of samples cut from the edges of the film after water absorption was almost the same value as that in the dry state. These results suggest that the absorbed water molecules are not uniformly dispersed in the film but are localized at the edges of the film even after the absorption equilibrium has been reached.

Constructing Novel High Dielectric Constant Polyimides Containing Dipolar Pendant Groups with Enhanced Orientational Polarization.

Polymer dielectrics with high dielectric constant are urgently demanded for potential electrical and pulsed power applications. The design of polymers with side chains containing dipolar groups is considered an effective method for preparing materials with a high dielectric constant and low loss. This study synthesizes and comprehensively compare the dielectric properties of novel polyimides with side chains containing urea (BU-PI), carbamate (BC-PI), and sulfonyl (BS-PI) functional groups. The novel polyimides exhibit relatively high dielectric constant and low dielectric loss values due to the enhanced orientational polarization and suppressed dipole-dipole interactions of dipolar groups. In particular, BU-PI containing urea pendant groups presents the highest dielectric constant of 6.14 and reasonably low dielectric loss value of 0.0097. The strong γ transitions with low activation energies derived from dielectric spectroscopy measurements have been further evaluated to demonstrate the enhanced free rotational motion of urea pendant dipoles. In energy storage applications, BU-PI achieves a discharged energy density of 6.92 J cm-3 and a charge-discharge efficiency above 83% at 500 MV m-1. This study demonstrates that urea group, as dipolar pendant group, can provide polymers with better dielectric properties than the most commonly used sulfonyl groups.

Crosslinked polyimides with bulky side-group polyhedral silsesquioxanes: Towards lower dielectric constant and better mechanical property

The synthesis of a low dielectric constant polyimide (PI) with a polyhedral oligomeric silsesquioxane (POSS) cross-linked structure is presented. A non-planar conjugated diamine monomer (FSNH2) with two -CH=CH2 reactive groups was first synthesised in a two-step process, and then two polyimides were synthesized by PSS-Octavinyl (OVPOSS) substituted, FSNH2 and dianhydride. OVPOSS cross-linked polyimides have good thermal stability and low dielectric constant. 6FDA-FSNH2-OVPOSS(6FPI-3) can reach a minimum dielectric constant of 2.08 (108 Hz) and a dielectric loss of 0.008 (108 Hz). In addition, the cross-linked structure of the OVPOSS and polyimide chains prevents the agglomeration of OVPOSS to a certain extent and improves the tensile strength and elongation at break of the polyimides, which has great application potential in large-scale integrated circuits.

Low dielectric post-cured benzocyclobutene-functionalized fluorine-containing polyimide material

Low dielectric constant (Dk) polyimide polymer materials are one of most attractive materials for their importance in microelectronic industries, such as high speed communication field. Herein, a novel benzocyclobutene (BCB) and trifluoromethyl functionalized diamine monomer (BFDA) was synthesized and used to prepare a series of co-polyimides with different BCB content (PI-BFs). Both trifluoromethyl and BCB structure can facilitate to low down Dk and dissipation factor (Df). For the cured PI-BFs, dielectric property test showed that the dielectric constant decreased significantly with the increase of BCB content, and the dielectric constant of PI-BF40% could reach 2.72 at 1 MHz. Besides, BCB can also contribute to improve glass transition temperature and initial storage modulus of PI-BFs. The Tg of PI-BF40% was 360 °C, and the initial storage modulus reached 2.83 GPa. Meanwhile, TMA test indicates that the post-curing by BCB group contributes to enhance the thermo-size stability. Moreover, PI-BFs show excellent thermal stability (Td5 > 499 °C), good transparency and low water uptake.

High dielectric constant polyimide for high-temperature film capacitor by tuning macroconjugated molecule

High dielectric constant polyimide for high-temperature film capacitor by tuning macroconjugated molecule

Temperature-Resistant Intrinsic High Dielectric Constant Polyimides: More Flexibility of the Dipoles, Larger Permittivity of the Materials.

High dielectric constant polymers have been widely studied and concerned in modern industry, and the induction of polar groups has been confirmed to be effective for high permittivity. However, the way of connection of polar groups with the polymer backbone and the mechanism of their effect on the dielectric properties are unclear and rarely reported. In this study, three polyimides (C0-SPI, C1-SPI, and C2-SPI) with the same rigid backbone and different linking groups to the dipoles were designed and synthesized. With their rigid structure, all of the polyimides show excellent thermal stability. With the increase in the flexibility of linking groups, the dielectric constant of C0-SPI, C1-SPI, and C2-SPI enhanced in turn, showing values of 5.6, 6.0, and 6.5 at 100 Hz, respectively. Further studies have shown that the flexibility of polar groups affected the dipole polarization, which was positively related to the dielectric constant. Based on their high permittivity and high temperature resistance, the polyimides exhibited outstanding energy storage capacity even at 200 °C. This discovery reveals the behavior of the dipoles in polymers, providing an effective strategy for the design of high dielectric constant materials.

The “fluorine impact” on dielectric constant of polyimides: A molecular simulation study

Fluorinated polyimides (PIs) with low dielectric constant (ε) have attracted increasing attention with the rapid development of advanced power electronics and 5G communication. In this work, the dielectric constants of three types of fluorinated PIs are firstly predicted by using two “Group contribution” methods, the Clausius-Mossotti method and the molecular dynamics (MD) simulation. The most reasonably good agreement is found between the MD simulated values and the previously reported experimental data. Secondly, the so-called “fluorine impact” from fluorine content (F%), molecular polarization (α/V), fractional free volume (FFV) and PI/water interaction energy (Einter) caused by the fluorine substituents on dielectric constant of the PIs are investigated. The substitution position and structure of the fluorine moieties demonstrate pronounced influence on dielectric constant when the PIs have similar fluorine content. Finally, the weight of each factor obtained by principal component analysis (PCA) is applied to assess an overall evaluation of the “fluorine impact”. α/V and F% are revealed to be the dominant factors to affect the dielectric constant. Based on the studied PI systems, a “negative” fluorine impact was attributed by a high α/V value. It can be speculated that the structure of PI-b1 provides an ideal pattern for designing new low-ε polyimides, i.e., increasing the amount of rigid di-substituted symmetric fluorine side chains with low molecular polarity in PI backbones.

Achieving Hydrophobic Ultralow Dielectric Constant Polyimide Composites: Combined Efforts of Fluorination and Porous Fillers

AbstractThe advancement of the microelectronics industry necessitates the use of interlayer insulation materials with low dielectric constants and high mechanical properties. In this paper, a new type of copolymerized fluorinated polyimide (PI) is synthesized, and mixed with polyhedral oligomeric silsesquioxane (POSS) functionalized mesoporous silica (MCM‐41@POSS). The PI/MCM‐41@POSS composites exhibit good hydrophobicity. With the addition of 3 wt% MCM‐41@POSS, the PI composite attained an ultralow dielectric constant (k = 1.88) and low dielectric loss (0.01) at 1 MHz, which is attributed to the mesoporous structure of MCM‐41 and the restriction of polarization in the bonded region. The decorated POSS effectively prevents the penetration of PI molecular chains into the mesopores of MCM‐41. In addition, the PI composites containing 3 wt% of MCM‐41@POSS obtain the highest maximum stress of 104.03 MPa with an elongation at break of 13.73%. The hydrophobic PI composites with ultralow‐k are expected to be good candidates as interlayer materials in microelectronics devices.

Preparation of Polyimide Films with Ultra-Low Dielectric Constant by Phase Inversion

Due to the high value of its dielectric constant, polyimide does not meet the requirements of the development of integrated circuits and high-frequency printed circuits. The development of novel low dielectric constant polyimide materials for the preparation of flexible copper clad laminates is of theoretical and practical significance in the application of polyimide for 5G communications. In this work, different fluorinated graphene/polyamic acids (FG/PAA) were used as the precursor, and the porous polyimide film was successfully prepared by phase inversion. The dielectric constant of the porous polyimide film is relatively low, being less than 1.7. When the content of fluorinated graphene is 0.5 wt%, the overall dielectric performance of the porous film is the best, with a dielectric constant of 1.56 (10 kHz) and a characteristic breakdown field strength of 56.39 kV/mm. In addition, the mechanical properties of the film are relatively poor, with tensile strengths of 13.87 MPa (0.2 wt%), 13.61 MPa (0.5 wt%), and 6.25 MPa (1.0 wt%), respectively. Therefore, further improving the breakdown resistance and mechanical properties of the porous film is essential for the application of porous ultra-low dielectric polyimide materials.

All‐organic polymer blend dielectrics of poly (arylene ether urea) and polyimide: Toward high energy density and high temperature applications

AbstractThe development of high‐performance dielectric films with high energy density and temperature stability is extremely desired for modern electronics and power systems. Herein, a simple and low‐cost approach is proposed to fabricate all‐organic blend films prepared from poly (arylene ether urea) (PEEU) and polyimide (PI) via solution casting and thermal imidization process. The incorporation of PEEU in PI matrix significantly improved dielectric breakdown strength and dielectric constant of PI. More precisely, blend film with 15 wt% PEEU exhibited highest energy density 5.14 J/cm3 at 495.65 MV/m, with enhanced dielectric constant of 4.73 and very low dissipation factor of 0.299%. Furthermore, the dielectric properties of the PEEU/PI blend displayed wonderful temperature stability in the range of − 50–+ 250°C, and great frequency stability between 10 and 106 Hz. The blend film also exhibited excellent heat resistance and presented valuable potential in thin film capacitors for high voltage direct current system.

Ultra-low dielectric constant polyimides: Combined efforts of fluorination and micro-branched crosslink structure

In the previous work, a micro-branched crosslink structure was constructed to molecular chain in the polyimide (PI) film of the 3,3′4,4′-biphenyltetracarboxylic dianhydride/1,4-phenylenediamine (BPDA/PDA) system by introducing a trifunctional monomer 1,3,5-tri(4-aminophenoxy) benzene (TAPOB). It was found that the micro-branched structure is instrumental in reducing the dielectric constant via increasing the free fraction volume (FFV) while the crosslink can lower the coefficient of the thermal expansion (CTE) through confining the chain movement. This helps to break the design contradiction between low dielectric and CTE, thereby realizing the synchronous optimization of the two. To further reduce the dielectric constant to meet the application requirements of modified PI (MPI) in 5G equipment, PI films were designed and prepared using pyromellitic anhydride (PMDA), 4,4′-(hexafluoroisopropyl) phthalic anhydride (6FDA), 4,4′-diaminobiphenyl ether (ODA), and 2,2′-bis(trifluoromethyl)-4,4′-diaminobipheyl (TFMB) as the monomers while TAPOB as the crosslinking agent, which involved four systems of PMDA/ODA/TAPOB, PMDA/TFMB/TAPOB, 6FDA/ODA/TAPOB, and 6FDA/TFMB/TAPOB. The influence of molecular chain stiffness and flexibility on the micro-branched crosslink structure was studied by means of experiment and molecular dynamic simulation, and PI films with lowered dielectric constant, which are expectably applicable in the electronics industry, were obtained.

Structure-property relationship of low dielectric constant polyimide fibers containing fluorine groups

A series of copolyimide (co-PI) fibers with low dielectric constants and excellent comprehensive properties have been successfully prepared via a two-step wet-spinning method by incorporating 2,2′-bis(trifluoromethyl)-4,4′-diaminobiphenyl (TFMB) into rigid polymer backbones of 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA)/p-phenylenediamine (p-PDA). The dielectric constant of PI fibers were substantially reduced from 3.0 to 2.48 at the frequency of 10 GHz after the introduction of trifluoromethyl (-CF3) groups. Meanwhile, the prepared PI fibers exhibited high thermal stability as well as excellent mechanical properties. The co-PI fibers possessed the optimum tensile strength of 1.4 GPa and modulus of 83.3 GPa at the p-PDA/TFMB molar ratio of 7/3. The 5% weight loss temperature in nitrogen ranged from 523 to 558 °C, and the glass transition temperature decreased from 372 °C to 295 °C with increasing TFMB contents. Both experimental and molecular simulations method were adopted to discuss the influence of fluorine group on the aggregation structure and properties of PI fibers, suggesting that the improved free volume were the crucial factor responsible for low dielectric constant. The molecular ordered degree and orientation degree of co-PI fibers decreased firstly and further increased with increasing TMFB content, which is due to the combined effects of large free volume of trifluoromethyl and polymer regularity variation caused by copolymerization.

Low Dielectric Constant Polyimide Obtained by Four Kinds of Irradiation Sources.

Irradiation is a good modification technique, which can be used to modify the electrical properties, mechanical properties, and thermal properties of polymer materials. The effects of irradiation on the electrical properties, mechanical properties, and structure of polyimide (PI) films were studied. PI films were irradiated by a 1 MeV electron, 3 MeV proton, 10 MeV proton, and 25 MeV carbon ion. Dielectric constant, dielectric loss, and resistance measurements were carried out to evaluate the changes in the electrical properties; moreover, the mechanical properties of the pristine and irradiated PI were analyzed by the tensile testing system. The irradiation induced chemical bonds and free radicals changes of the PI films were confirmed by the Fourier transform infrared (FTIR) spectra, X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance (EPR). The dielectric constant of the PI films decreases with the increase of fluences by the four kinds of irradiation sources.

Low dielectric constant polyimide mixtures fabricated by polyimide matrix and polyimide microsphere fillers

AbstractPolyimide microspheres were prepared via non‐aqueous emulsion polymerization by using pyromellitic dianhydride (PMDA) as anhydride monomer and 2,2‐bis(4‐(4‐aminophenoxy)phenyl)propane as amine monomer. The polyimide microspheres were well characterized by Fourier transform infrared spectroscopy, SEM and laser particle size analyzer. They were spherical in shape and monodisperse and their size was 31–33 μm. Polyimide mixtures formed by polyimide microspheres as fillers and polyimide composed of pyromellitic and dianhydride 4,4′‐oxydianiline (ODA) as matrix were investigated with regard to thermal properties, dielectric properties and mechanical properties. With 10%–50% polyimide microspheres in the polyimide mixtures, the dielectric constants were 2.26–2.48 (1 MHz) and the loss tangents were 0.00663–0.00857 (1 MHz), which were both significantly lower than the values for ODA‐PMDA polyimide. The decomposition temperature and glass transition temperature were above 440 and 290 °C. The polyimide mixtures possessed excellent thermal resistance. When the percentage of polyimide microsphere addition was 30%, the polyimide mixtures had the largest tensile strength (128.50 MPa) and elongation at break (9.01%). These results indicate that the polyimide microspheres were used as both low dielectric fillers and reinforcing fillers. © 2020 Society of Chemical Industry

Low Dielectric Constant Polyimide Hybrid Films Prepared by in Situ Blow-Balloon Method

Insulating materials with a low dielectric constant and a low dielectric loss are in high demand to meet requirements of the continuous miniaturization of electronic devices and high speed informat...

Imparting low dielectric constant and high modulus to polyimides via synergy between coupled silsesquioxanes and crown ethers

Our pilot research revealed that the dielectric constant of polyimide (PI) can be reduced and the modulus can be improved by assembling necklace-like interlocking complexes with crown ethers. Not only did we find that these properties of the PI complex still cannot adequately meet the demand of practical applications but also that there was a deterioration in its thermal stability. A functional octa(aminopropyl)silsesquioxane (OAPrS) with a significantly rigid Si-O-Si cage was incorporated into an 18-crown-6 (CE6)-PI (CE6-PI) complex to produce inorganic-organic OAPrS/CE6-PI nanocomposites. By exploiting the synergetic effect of OAPrS and CE6, most properties of the PI were clearly improved. In the case of 3.9 wt% OAPrS and 7.8 wt% CE6, the dielectric constant of PI was reduced by 30%, and Young's modulus and the tensile strength were increased by 106% and 23%, respectively. In addition, the thermal stability of the CE6-PI complex was modified, and its 5% weight loss temperature and glass transition temperature were increased by 31.2 and 11.2 °C, respectively, with the incorporation of 3.9 wt% OAPrS. The indispensable nano-reinforcing role of aggregated OAPrS crystal in the nanocomposite was carefully analysed and verified.

Intrinsic low dielectric constant polyimides: relationship between molecular structure and dielectric properties

By increasing the number of benzene rings in the pendant group, the dielectric constant of the as-prepared polyimides can be effectively decreased.

Facile method for fabricating low dielectric constant polyimide fibers with hyperbranched polysiloxane

High-performance fibers with a low dielectric constant and good mechanical properties as well as excellent thermal stability are in demand for the next generation of advanced radar-wave-transparent composites.

Low dielectric behavior of amine functionalized MCM-41 reinforced polyimide nanocomposites

A class of low dielectric constant polyimide (PI) composites was prepared by means of reduced polarization. Consequently, the nonpolar group of long aliphatic chain bridged diamine was synthesized and utilized to prepare PI with pyromellitic dianhydride and subsequently the porous amine-functionalized mobil composition of matter no. 41 (FMCM-41) was synthesized and reinforced into the PI matrix with a view to reduce the value of dielectric constant of PI. Various analytical techniques such as Fourier transform infrared, proton nuclear magnetic resonance, and carbon nuclear magnetic resonance were used to characterize and confirm the synthesized monomer and polymer. The porous nature of hybrid polymer nanocomposites was ascertained using transmission electron microscopic images, and the aggregations of nanoparticles were confirmed by scanning electron microscopic images. The mechanical (tensile) and dielectric behaviors of a material were ascertained by the measurement of porosity. The optimum concentration of FMCM-41-reinforced PI (7 wt% FMCM-41/PI) has the lowest value of dielectric constant of 2.21 at 1 MHz, and beyond this concentration (10 wt% FMCM-41/PI), the reverse trend was observed in the values of dielectric constant and dielectric loss, due to the agglomeration of silica nanoparticles in the PI matrix.

Synthesis and properties of highly organosoluble and low dielectric constant polyimides containing non-polar bulky triphenyl methane moiety

Novel fluorinated aromatic polyimides were prepared by the conventional two-step imidization of 4.4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) and diamines (TriPMPDA and TriPMMDA) bearing triphenyl methane moiety. Both of the flexible and tough polyimide films exhibited an intrinsic low dielectric constant (low-k) values of 2.56 and 2.33 at the frequency of 10kHz, respectively, due to the introduction of the bulky triphenyl methane side groups and the tortuous backbone structures. In addition, they showed light color, high thermal stability, moderate mechanical property, and more importantly, excellent solubility in common organic solvents (even completely dissolved in dichloromethane and chloroform). Thus, both of the functional polyimides possessed attractive potential applications in the field of high performance flexible polymer interlayer materials.