Low Dielectric Properties Research Articles

Synthesis and characterizations of polystyrene materials with low dielectric constant and low dielectric loss at high frequency

AbstractIn this article, a facile and efficient approach to the modification of polystyrene (PS) materials with low dielectric properties at high frequency is reported. A series of N‐acetoxy amide (AA)‐containing polystyrenes (PSAAs) synthesized by free‐radical polymerization can be transformed into NCO‐containing polymers (rPSAAs) via Lossen rearrangement reaction of the AA group. The modified PS materials were then obtained by reacting the rPSAAs with hydroxyl‐terminated poly(phenylene oxide) (PPOD), polybutadiene, and amino‐terminated polysiloxane, respectively. The thermal stability, mechanical, and dielectric properties of PPOD‐modified PS materials were improved with increase of PPOD content. The PPOD (20 wt%)‐modified PS had a dielectric constant of 2.22 and dissipation factor of 1.65 × 10−3 at 10 GHz. This work provides an easy and effective method to prepare high performance modified PS materials by introducing poly(phenylene oxide), which could meet the requirement of new‐generation communication technology.

Design of polyarylates containing tert‐butyl cyclohexyl bulky side group with high transparency and low dielectric properties

AbstractA new kind of novel low dielectric constant (Dk) and high transparency polyarylate had been synthesized through interfacial polycondensation with 1,1′‐ bis (4‐hydroxybenzene)‐4‐tert‐butylcyclohexane (Bt‐BPZ) containing tert‐butyl cyclohexyl bulky side group. As we expect, that the introduction of tert‐butyl cyclohexyl with large free volume is proved to be an efficient strategy for obtaining low dielectric constant and high transparency polyarylate. The optimal dielectric property is obtained with 90% Bt‐PZA in polyarylate (Bt‐PZA91), which show aDkas low as 2.14 at 1 MHz. Meanwhile, Bt‐PZA91 also demonstrates good transmittance of 81.08%–88.34% at 450 nm and 78.67–88.26 at 400 nm. The cut‐off wavelength of Bt‐PZA91 is 304 nm, which is 16 nm shorter than commercial product U‐100 (λc: 320 nm). In addition, the resultant polyarylates showed good comprehensive performance such asTgof 202.2–220.5°C,Td 5%(the initial thermal degradation temperature) of 455.4–468.4°C, tensile strength of 64.7–86.8 MPa and low water absoption (0.41% of Bt‐PZA91). Also it was found to can be thermal process, that its convenient thermoplastic processability makes it a great candidate for light‐electronic industry, 5G communication, and we believe that Bt‐PZA will have a broad application prospect.

Furfural-based P/N/S flame retardant towards high-performance epoxy resins with flame retardancy, toughness, low dielectric properties and UV resistance

The development of high-performance EP composites with high glass transition temperature (Tg), excellent flame retardancy, and UV resistance is a challenging topic in the flame retardancy community. In this work, a bio-based phosphorus/nitrogen/sulfur (P/N/S) containing flame retardant (FDI) was prepared from furfural, 2-amino-5-nitrothiazole, and DOPO. It was applied to improve the flame retardant, dielectric, and UV-resistant properties of EP. Thanks to the combination of phosphorus, nitrogen, and sulfur in FDI, the EP/FDI composites showed superior flame retardancy. Only adding 5 wt% FDI made EP achieve UL-94 V-0 flammability rating with a limiting oxygen index (LOI) of 27%. Meanwhile, EP/FDI-5% composite showed significant reduction of 65.1% and 33.6% in total smoke production (TSP) and the peak heat release rate (pHRR), respectively. The flame-retardant mechanisms of EP/FDI thermosets were investigated by residual char photographs, SEM, XPS, and Py/GC-MS. Moreover, compared to pure EP, EP/FDI composites showed excellent UV resistance, low dielectric properties, and high glass transition temperature, which was expected to be extensively used in multiple areas of production.

High-Branched Organosilicon Epoxy Resin with Low Viscosity, Excellent Toughness, Hydrophobicity, and Dielectric Property

Rapidly developing technology places higher demands on materials, thus the simultaneous improvement of materials' multiple properties is a hot research topic. In this work, a high-branched silicone epoxy resin (QSiE) was synthesized and applied to the curing system of bisphenol A epoxy resin (DGEBA) for modification investigations. When 6 wt% QSiE was added to the system, the viscosity dropped by 51.8%. The mechanical property testing results indicated that QSiE could significantly enhance the material's toughness while preserving good rigidity. The impact strength was enhanced by 1.31 times when 6wt% of QSiE was introduced. Additionally, the silicon skeleton in QSiE has low surface energy and low polarizability, which could endow the material with good hydrophobic and dielectric properties. This work provided a new idea for the preparation of high-performance epoxy resin additives, and provided a broad prospect for cutting-edge applications of epoxy resins.

Perfluoropolyether methyl propionate polysiloxane coating with high hydrophobicity and low dielectric property

AbstractDeveloping materials with a combination of superior properties such as hydrophobicity and low dielectric is very challenging. This work proposes a design strategy based on the synergistic effect of silicon fluorine to fabricate fluorous silicon materials with excellent hydrophobicity and dielectric properties. Perfluoropolyethyl propionate polysiloxane (PEPS) with different grafting ratios was synthesized by the reaction of polymethylhydrosiloxane (PMHS) and perfluoropolyethyl methacrylate (PPM) hydrosilane. The self‐crosslinking perfluoropolyether methyl propionate polysiloxane (PFSP) coating with good hydrophobicity and low dielectric was prepared by further introducing triethoxyvinylsilane (TOVS) into the PEPS and condensing. The fluorine content of two interfaces (film PET and film air) of PFSP‐4 film was analyzed by XPS, and it was found that the fluorine content of the film air interface was 46.19% and that of the film PET interface was 17.3%. With the increase of perfluoropolyether content in PFSP, fluorine‐containing groups migrate to the coating surface, which is more conducive to enhancing the hydrophobicity of the coating. The results indicate that the film has excellent hydrophobicity with a high water contact angle of up to 117° due to the introduction of PPM. In addition, the dipole moment of perfluoropolyether methyl methacrylate is 2.27, which is lower than that of methyl. Therefore, the introduction of a large number of perfluoropolyether bonds effectively reduces the polarity of the material, which is beneficial to its low dielectric properties. The dielectric constant of PFSP‐4 is 2.4, which is 33% lower than that of a fluorine‐free silicone coating. The results show that the self‐crosslinking perfluoropolyether methacrylate polysiloxane coating has excellent hydrophobicity and low dielectric properties, so it has a feasible application prospect in the electronic industry.

Structuring multiscale porous architecture in polyether sulfone films for ultra-low dielectric constant

Ultra-low dielectric constant materials possess a broad prospect for application in microelectronics devices and communication systems. The most efficient method for fabricating low dielectric constant materials is the incorporation of porous structure into the materials. However, it is vital and remains a great challenge to precisely control the size, distribution and number of pore structures for porous films to maintain comprehensive properties. Herein, a series of novel multiscale porous polyether sulfone-polyhedral oligomeric silsesquioxanes (PES-POSS) films with ultra-low dielectric constants were fabricated by solvent phase inversion approach. Specifically, the prepared PES-60%POSS (P60) films demonstrate an ultra-low dielectric constant and dielectric loss of 1.31 and 0.00078 at 1 kHz. Multiscale pores ranging from micron to nano and low molar polarization of POSS nano-hybrids are the key to its low dielectric properties of the resultant materials. Moreover, the interface enhancement by the covalent bonding of POSS and PES skeleton ensures that the composite hybrid films maintain reliable thermal and mechanical properties while possess low dielectric properties. The measurements of contact angle and water absorption show the PES-POSS films have favorable water resistance. That is beneficial to the dielectric stability and service life of films. In addition, the average transmissivity coefficient of P60 films in X-band is high up to 95.6%, which show the potential of application as an excellent wave transmitting material.

Structural, optical and dielectric investigations on RECr0.85Mn0.15O3 (RE = Ho, Gd and Pr) nanoparticles

We hereby report the room-temperature structural and optical characterization of RECr0.85Mn0.15O3 (RECMO, RE = Ho, Gd and Pr) compounds synthesized by the auto-combustion sol–gel route. Their low temperature dielectric properties are also presented. The RECMO compounds crystallize in an orthorhombic Pbnm symmetry with an average grain size range of 51–80 nm. Structural analysis reveals an increase in the structural distortion compared to that of the undoped bulk compounds. Optical measurements exhibit a significant reduction in bandgap values for RECMO nanoparticles when compared with their undoped bulk compounds. Further, from the absorbance measurements various optical parameters such as skin depth, extinction coefficient, refractive index and optical conductivity were also calculated. The dielectric analysis confirms the lower values of the dielectric permittivity and dielectric loss than those of their corresponding bulk compounds. AC conductivity versus frequency and temperature data are fitted according to the Jonscher’s power law and Arrhenius law, respectively. The small polaron hopping is responsible for the electric conduction in these compounds. The tunability of the optical and dielectric properties as a result of substitution and particle size reduction makes these materials useful for various potential applications in photocatalysis, optoelectronics and low permittivity dielectrics.

Multilayer In-Plane Heterostructures Based on Transition Metal Dichalcogenides for Advanced Electronics.

In-plane heterostructures of transition metal dichalcogenides (TMDCs) have attracted much attention for high-performance electronic and optoelectronic devices. To date, mainly monolayer-based in-plane heterostructures have been prepared by chemical vapor deposition (CVD), and their optical and electrical properties have been investigated. However, the low dielectric properties of monolayers prevent the generation of high concentrations of thermally excited carriers from doped impurities. To solve this issue, multilayer TMDCs are a promising component for various electronic devices due to the availability of degenerate semiconductors. Here, we report the fabrication and transport properties of multilayer TMDC-based in-plane heterostructures. The multilayer in-plane heterostructures are formed through CVD growth of multilayer MoS2 from the edges of mechanically exfoliated multilayer flakes of WSe2 or NbxMo1-xS2. In addition to the in-plane heterostructures, we also confirmed the vertical growth of MoS2 on the exfoliated flakes. For the WSe2/MoS2 sample, an abrupt composition change is confirmed by cross-sectional high-angle annular dark-field scanning transmission electron microscopy. Electrical transport measurements reveal that a tunneling current flows at the NbxMo1-xS2/MoS2 in-plane heterointerface, and the band alignment is changed from a staggered gap to a broken gap by electrostatic electron doping of MoS2. The formation of a staggered gap band alignment of NbxMo1-xS2/MoS2 is also supported by first-principles calculations.

A promising low‐dielectric‐constant material with good comprehensive performance upon heating

AbstractThe dielectric and other properties of low‐dielectric‐constant materials after heating are crucial to their performance and use, but rarely studied. In this article, sandwich‐type porous polyimide (PI) film in which porous structures located on both upper and lower surfaces of flat PI film was prepared through the simple, low‐cost and green microemulsion method. The porous structures were preserved after heating due to the usage of thermally stable fluorine‐contained PI (FPI) and PI as skeleton and substrate of the porous structure, respectively, but with the increase of pore size because of the removal of thermally unstable surfactant on the inner surface of the pores. More importantly, 2.89%–5.57% of reductions in the dielectric constant with the maintenance of low dielectric loss and water absorption and high mechanical strength were observed after heating. Therefore, the low dielectric properties of heated films were well preserved upon high humidity treatment. Moreover, the structure and properties of the heated films could be adjusted via controlling the parameters in the microemuslion method. These excellent properties after the high‐temperature treatment facilitate the application of the sandwich‐type porous PI film as dielectric materials in high‐temperature environment.

Ordered/Disordered Structures of Water at Solid/Liquid Interfaces

Experiments and theory have revealed versatile possible phases for adsorbed and confined water on two-dimensional solid surfaces, which are closely related to the aspects of various phenomena in physics, chemistry, biology, and tribology. In this review, we summarize our recent works showing that the different water phases with disordered and ordered structures can greatly affect surface wetting behavior, dielectric properties, and frictions. This includes the ordered phase of water structure that induces an unexpected phenomenon, an “ordered water monolayer that does not completely wet water”, at T = 300 K on the model’s surface and some real, solid material, together with the anomalous low dielectric properties due to ordered water.

Three-layer composite coatings with compatibility of low infrared emissivity and high wave transmittance

The study of infrared stealth-compatible, electromagnetic wave-transparent technology is currently receiving a lot of attention due to the functional specificity of the equipment, such as radomes. In this study, a new method of layered spraying was used to construct three-layer composite coatings, in which each layer was sprayed with a different formulation of paint. By adjusting the content of aluminum powder in each layer and keeping the content of carbon fiber (CF) at 4 wt%, the three-layer composite coatings achieved a balance of dielectric property, antistatic performance, and low infrared (IR) emissivity. The A3-A0-A0 composite coating, which matched the parameters for low IR emissivity and low dielectric property, had an IR emissivity of 0.498, a dielectric constant at 9.375 GHz of 6.23, and a dielectric loss of 0.038. The findings demonstrate that the aluminum powder content of the topmost layer had the sole significant impact on the three-layer composite coatings' IR emissivity, although the dielectric constant was strongly associated with the coating's overall aluminum powder content. The novel three-layer composite coating offers a brilliant concept for the study and development of materials that are compatible with wave transmission and infrared stealth.

Manipulative pore-formation of polyimide film for tuning the dielectric property via breath figure method

Polyimide (PI) films have been extensively used in the field of microelectronic as insulating materials. With the rapid development of microelectronic devices towards miniaturization and large power, the development of low dielectric properties of PI materials has attracted more and more attention. In this study, the breath figure (BF) process was used to prepare single-layered and multi-layered microporous PI films, for obtaining the low dielectric properties. The BF porous structure of PI film was successfully constructed by two implementing strategies, i.e., solution casting for direct preparation of PI film and solvent treatment upon pre-shaped PI film for in-situ pore-formation. By changing solution concentration, environmental humidity and temperature, efficient manipulation of the pore morphology of the film both on the surface and in the bulk layer was achieved. Such multi-layered porous BF structure has been proved to significantly lower the dielectric constant of PI film, from 3.7 of non-porous film to 1.7 of porous film. In order to further expand the application range of BF microporous PI film, both ways of alkali treatment and thermal oxidation were taken for the cross-linking of the porous PI films, greatly improving the solvent resistance of the film. The original porous morphology was completely retained, ensuring that the low dielectric properties were not affected. This is the first report on the preparation of multi-layered microporous low dielectric PI films by BF process.

Enhanced dielectric properties of Be-doped magnesium oxide nanopowder

Owing to its applicability in refractory ceramic synthesis, nanoelectronics, optoelectronic and sensing devices, and superconducting products, magnesium oxide (MgO) is recognized to be an important ceramic material. However, it has a relatively low dielectric constant compared to other metal oxide semiconductors, which restricts the range of its bandgap and limits its applicability. Therefore, in this study, we propose and verify a method to improve the dielectric constant of MgO. A sample of MgO powder doped with Be ions was prepared using the Pechini method. The crystal structure of the doped MgO powder was analyzed by x-ray diffraction. Through structural analysis, it was confirmed that a substitution amount of up to 5% of Be ions was possible without breaking the cubic structure. The bonding structure in the lattice of the sample was identified through x-ray photoelectron spectroscopy, and the change in the bonding structure according to the amount of substitution was identified. The dielectric properties of the samples were analyzed as a function of frequency at room temperature. The real and imaginary parts of the dielectric constant were studied at room temperature as a function of frequency and composition. It was confirmed that the dielectric constant increased as the Be ions were substituted. Our results show that improving the low dielectric properties of pure MgO can enable its application to wide bandgap and high voltage applications simultaneously.

Effects of wood fiber on the properties of silicoaluminophosphate geopolymer

Silicoaluminophosphate geopolymer is an important class of inorganic cementitious material, which attracts increasing attention due to the excellent mechanical properties, high thermal resistance and low dielectric properties. However, like most of the pristine or unreinforced cement based materials, silicoaluminophosphate geopolymer still suffers from brittle failure, which seriously limits its popularization and application. Based on the characteristics that silicoaluminophosphate geopolymer is almost a Ca-free material forming in acidic environment and driving by the demands of low carbon, environmental friendly and low cost, this paper adopts wood fiber as a reinforcing material to improve the toughness of silicoaluminophosphate geopolymer. Results show that the incorporation of wood fiber can effectively reduce the brittleness and increase the fracture toughness of silicoaluminophosphate geopolymer by the excellent bonding performance between reaction products and wood fiber. However, the addition of wood fiber is unfavorable to the setting and hardening behaviour, reaction degree and compressive strength of silicoaluminophosphate geopolymer. Although the hydrolysis of wood fiber in acidic environment results in some local defects on its surface, these defects have little effect on the improvement of silicoaluminophosphate geopolymers toughness due to the repairing effect of reaction products.

Directing Quasiparticle Movement in Graphitic Carbon Nitride through Spatial Engineering for Enhanced Photocatalytic Hydrogen Evolution

The inherently low dielectric properties of polymeric semiconductors lead to high exciton binding energy, impeding the photogenerated electron and hole separation. The aim of this work is to regulate the spacing of charge through spatial engineering in graphitic carbon nitride (CN), which performs photocatalysis through dual routes, where ruthenium phosphide (RuxP) and hydroxide ions (OH–) serve as the electron acceptor and hole extractor, respectively. The unique heterojunction of RuxP incorporated in the bulk CN (B-RuxP-CN) shows a lower exciton binding energy (61 meV) than bare CN and CN surface-deposited RuxP (S-RuxP-CN). This favors high carrier density and rapid escape of active electrons from bound excitons. The photocatalytic hydrogen (H2) evolution rate of B-RuxP-CN increases with increasing pH. However, S-RuxP-CN maintains an almost invariable H2 production rate even with similar increases in pH. We reasonably ascribe the different H2 evolution performances of both photocatalysts to their contrasting structures and discrepancy in quasiparticle relaxation dynamics. The wrapped structure of B-RuxP-CN endows it with a prolonged charge separation lifetime (189 ns) and an enhanced H2 evolution rate (32.0 μmol/h) in an alkaline scavenger solution. This work provides a controllable procedure for quasiparticles’ directional movement in polymeric photocatalysts.

Low Dielectric Properties and Transmission Loss of Polyimide/Organically Modified Hollow Silica Nanofiber Composites.

In this study, a series of low dielectric constant and transmission loss of polyimide (PI)/organically modified hollow silica nanofiber (m-HSNF) nanocomposites were synthesized via two-step polymerization. Two different PIs were fabricated using two types of diamine monomers with or without fluorine-containing groups and biphenylene structure of dianhydride. The chemical structure and morphology of the fabricated composites were characterized using Nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) and field-emission scanning electron microscopy (FESEM). The two-step polymerization process successfully manufactured and converted from polyamic acid to polyimide after thermal imidization was proved by the NMR and FTIR results. The FESEM and their related energy-dispersive X-ray spectroscopy (EDS) images of nanocomposites indicate that the m-HSNF is extremely dispersed into the polyimide matrix. The high-frequency dielectric constants of the nanocomposite materials decrease as the presence of fluorine-containing groups in diamine monomers and the loadings of the m-HSNF increase. These findings are probably attributed to the presence of the steric hindrance effect brought by trifluoromethyl groups, and the m-HSNF can disrupt the chain packing and increase the free volume, thus reducing the dielectric properties of polyimides. The transmission loss and its related uncertainty of fabricated composite materials contain excellent performance, suggesting that the fabricated materials could be used as substrate materials for 5G printed circuit board.

Effect of modification of zinc oxide nanostructures on contact angle

The hydrophobic coatings are one of the most used processes to prevent the deterioration of materials and increase its lifetime, since they have non-stick, low friction, anti-wetting, high and low temperature resistance, chemical and dielectric properties, etc. This work presents the chemical production of zinc oxide (ZnO) nanostructures that were deposited on glass substrates by two methods: spin-coating and dip-coating. The doped substrates were modified by temperature and exposure to ultraviolet light (UV). The contact angle of the surface was measured after making some modification, revealing an initial change compared to the uncoated substrate. Later, the angles were varied, comparing between the two deposition methods. The higher contact angle was presented by spin-coating sample, after rising its temperature and a first exposure to UV light; an increase of 30% was observed in comparison to the uncoated substrate; In contrast, the smallest angle was obtained in dip-coating sample after raising its temperature, reducing around 55% of its size compared to the uncoated substrate.

Low Dielectric Constant and Anisotropic Mechanical Properties of Dispenser‐Printed Polyetherimide Films Using Two‐Step Thermal Treatment

Back Cover: In article 2200213 by Jae-Do Nam and co-workers, polyetherimide-based ink is printed using dispenser printing, which is facile and has an advantage in shape flexibility. The randomly distributed polymer chains can be aligned following the printing directions resulting in characteristic anisotropic mechanical properties.

Synthesis and preparation of biobased benzoxazine/bismaleimide copolymers: Thermal, mechanical and dielectric properties

Preparation of low dielectric thermosetting resins by green method is a challenging subject. Herein, unique bio-based benzoxazine monomer E-dea was prepared by a solvent-free method using eugenol as phenol source, and then E-dea and bismaleimide (BMI) were copolymerized to prepare poly(E-dea/BMI-0.86) and poly(E-dea/BMI-1). The comprehensive properties including thermal, mechanical and dielectric properties of the copolymers were studied. Notably, poly(E-dea/BMI-0.86) and poly(E-dea/BMI-1) exhibit low dielectric properties with dielectric constants of 2.85 and 2.79 at 1 MHz, respectively. Besides, the glass transition temperature (Tg), the initial thermal decomposition temperature (Tdi) and the flexural strength of poly(E-dea/BMI-0.86) and poly(E-dea/BMI-1) are 167 °C and 169 °C, 333 °C and 321 °C and 115 ± 3.5 MPa and 123 ± 4.9 MPa, respectively. The excellent comprehensive performance is attributed to the interaction between flexible and low dielectric decane segments and rigid oxazine and BMI segments.

Novel hybrid silicone resin composites with excellent low dielectric and high temperature mechanical properties

With the development of aerospace technology, the temperature resistance of traditional silicone resins fails to satisfy the ever-increasing demand from the stringent application conditions. In this paper, we used diphenyl sulfide (TBSP), diphenyl sulfoxide (SIBSP), and diphenyl sulfone (SODP) to modify the main chain of SiR by hydrolysis-condensation and prepared the quartz fiber reinforced SiR composites. The mechanical properties of QF@SiR composites were measured, and the effects of temperature on the mechanical properties were investigated. Compared with QF/SiR, the ILSS and bending strength of QF/SiR@SODP composites enhanced from 15.58 MPa to 183.59 MPa–25.36 MPa and 338.37 MPa at room temperature. Moreover, at 500 °C, the ILSS and bending strength of QF/SiR@SODP were 11.87 MPa and 114.37 MPa, representing an enhancement of 514% and 315% compared with SiR composite. The structural, heat resistance and composition changes of the composites were determined by SEM, TG and IR, and the failure mechanism of the composites at high temperature was elucidated.