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The continuous upgrading of electronic technology has facilitated the integration and miniaturization of electronic and electrical equipment, as well as putting great pressure on the multifunctional demand for internal materials. Developing insulating materials with both low permittivity and high thermal conductivity has become imperative. This perspective focuses on polyimide (PI), which is the top material of the polymer material pyramid, discusses the characteristic parameters that affect its dielectric property and thermal conductivity. A series of basic schemes to regulate the dielectric/thermal properties of PI are summarized, revealing the bottlenecks and drawbacks of the current research. Future development trends of PIs featured low permittivity-high thermal conductivity are anticipated, and novel ideas are proposed for the development of new generation of multifunctional PIs. [ABSTRACT FROM AUTHOR]

The 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. [ABSTRACT FROM AUTHOR]

Ultralow dielectric permittivity (k=2.58) nanohybrid dielectric film was obtained by dispersing 3.0 wt % mesoporous silicate (MCM-41) particles with nanosize hollow channels into polyimide (PI) polymer. The ultralow k value of the hybrid film can be mainly attributed to the low k value of MCM-41 itself and the small air gaps in the hybrid films. High volume resistivity and high breakdown strength were also observed for those films. At high concentration of MCM-41 loading (>3.0 wt %), the k values of the films increased significantly due to the contribution of strong interfacial polarization and interaction among MCM-41 particles. The ultralow k feature of the PI/MCM-41 nanohybrid films was explained well by Maxwell–Garnett and Bruggeman equations. The PI/MCM-41 nanohybrid film with good thermal stability as well as excellent dielectric properties can be considered as good candidate for advanced dielectric materials. [ABSTRACT FROM AUTHOR]

For practical application, studying the mechanism governing the macroscopic dielectric properties of polymer composites at low concentration is of great significance. A three-dimensional (3D) representative model with randomly dispersed grains in polymer matrix has been established and calculation results of effective permittivity of BT/PVDF composites with finite element method (FEM) show good consistency with experimental measurements, which demonstrate that the distribution of electric field in ceramic particles/polymer composites at low concentration can be approximated by the electrostatic field. Furthermore, the relationship between the internal electric field and dielectric properties of composites has been established. The effect of grain size in submicron and its dielectric constant to the effective permittivity of composites are fully investigated. The former shows of negligible significance compared with the evident effect of volume fraction, while the latter presents saturation as increasing the permittivity ratio between ceramic particle and polymer. [ABSTRACT FROM AUTHOR]

Block polypropylene (BPP) is an eco-friendly material that has a good potential for cable insulation because of its high melting point and excellent electrical properties. To further improve the electrical insulation properties of BPP, 1 wt% Al2O3 nanoparticles were added by melt blending to BPP. The electrical properties of the BPP/Al2O3 composite were measured at 25 and 70 °C. The results show that the trap density increases by 3.2 times that of unfilled BPP. The conduction current in BPP and BPP/Al2O3 composite decreased at 25 and 70 °C. The electrical breakdown strength of the composite also increases compared to BPP. Space charge accumulation is significantly suppressed in the composite at 70 °C. The results indicate that the improvements in electrical properties, especially the space charge suppression in the composite, can be attributed to the higher trap density. Permittivity and dielectric loss show little effect on temperature. The permittivity of the composite shows a slight increase which can be attributed to the higher permittivity of the Al2O3 nanoparticles. [ABSTRACT FROM AUTHOR]

High-permittivity (high- k ) materials play a key role in advanced electronics and electrical power systems. How to prepare the flexible material with high permittivity and low dielectric loss turns out to be a hard work due to the essential low permittivity of polymers. In this work, a kind of ductile polymer-based composites was fabricated by incorporating ionic liquids into polymer matrices. The optimized permittivity of composite with 50 wt% ionic liquid reached up to 3.3 × 10 4 , while the dielectric loss was as low as 0.65. The temperature dependence of dielectric properties was also investigated, and a high permittivity as well as low dielectric loss at 100 Hz of about 2.0 × 10 4 and 0.23 were achieved at 80 °C, respectively. Furthermore, the study reveals that the dielectric loss peaks of the composite films can be affected by the content of ionic liquid, temperature even the size of ions. In short, the finding indicates that the addition of ionic liquids into polymers provides a big opportunity to improve dielectric properties of polymer materials. [ABSTRACT FROM AUTHOR]

Flexible polymer based materials with excellent breakdown strength and weak space charge behavior have been widely used in the field of cable insulation and cable termination. The silicon carbide (SiC) is beneficial to homogenize the electric field distributions, suppress the space charge injection and enhance the dissipation in the polymer composite. In this work, the polydimethylsiloxane (PDMS) based composites filled with β-SiC nanoparticles were prepared by solution mixing and mechanical blending, respectively. Compared with the pure PDMS, the SiC/PDMS composites possess not only the increased nonlinear conductivity coefficient but also the largely enhanced capability of dissipation of space charge. Especially under high electric field environment, the impact caused by uneven distribution of the SiC fillers was significant. The results of the space charges measurement under high electric field revealed that the SiC nanoparticles could largely enhance the dissipation and accelerate the movement of space charge, which was due to less trap sites leading to the better dispersion of SiC nanoparticles. [ABSTRACT FROM PUBLISHER]

ABSTRACT The properties of the polymer nanocomposites (PNCs), consisting low density polyethylene (LDPE) and magnesium oxide nanoparticles (MgO-NPs), were systematically discussed in this paper. The shear mixing time and MgO concentration were considered as the two factors affecting the dispersion state, which was found to be effective to change the crystallinity and the mechanical performance of MgO/LDPE PNCs. A reduction in the dynamic shear viscosity was observed when the concentration of MgO-NPs at a relative low level, which was also dominant by the dispersion states of MgO-NPs. Evident enhancement of the static yield stress was revealed only by introducing a minute amount of MgO-NPs (0.25 wt %). Meanwhile, the elastic and loss modulus were also found to be dependent on the dispersion state of MgO-NPs. A positive increase in dielectric permittivity was identified by uniaxial stretching the MgO/LDPE PNCs strips owing to the orientation enhancement of internal microstructure. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43038. [ABSTRACT FROM AUTHOR]

A series of BaxSr1-xTiO3 (x=0.2, 0.4 and 0.6, BST) ferroelectric ceramics were prepared by conventional solid state reaction method. Crystal structure, surface morphology and dielectric properties of the BST ceramics and polyimide (PI)/BST composite films were analyzed using X-ray diffraction, scanning electron microscopy and dielectric spectroscopy, respectively. As the value of x increases from 0.2 to 0.6, the dielectric permittivity (ε) of PI/BST composite films increased, while their dielectric loss (tan δ) decreased. The PI/Ba0.6Sr0.4TiO3 composite films possessed the larger ε of 24 at 102 Hz, which is almost twice higher than that of the PI/Ba0.2Sr0.8TiO3 one. It was attributed to the Maxwell-Wagner behavior between PI matrix and BST ceramic particles, resulting in the larger ε of ceramics. Besides, the PI/Ba0.6Sr0.4TiO3 demonstrated the lower tan δ of 0.004 at 102 Hz, which showed broad temperature dependence. Therefore, the PI/Ba0.6Sr0.4TiO3 flexible material has a potential application as excellent microwave dielectrics. [ABSTRACT FROM PUBLISHER]

In this work, core-shell structured BaTiO3/polystyrene nanoparticles (BT-PS) with different thickness of PS shell were synthesized through atom transfer radical polymerization and the influence of their shell thickness on dielectric properties of BTPS/ PS composites was studied. Two types of BT-PS with the PS shell of 3 nm or 12 nm were obtained by controlling the polymerization time. The structure of BT-PS was carefully characterized by infrared spectroscopy, X-ray diffraction, thermal gravimetric analysis, and transmission electron microscope. The results confirmed the successful preparation of core-shell BT-PS nanoparticles. Compared to pristine BT, the core-shell particles can be more homogeneously dispersed into PS matrix. As a result, higher dielectric constant, higher breakdown strength, and lower dielectric loss were achieved in BT-PS/PS composites. Moreover, the dielectric constant of BT-PS/PS composites displayed frequency independent behavior. In addition, the composites filled by BT-PS with 3 nm of PS shell showed better dielectric properties than those filled by BT-PS with 12 nm of PS shell. A maximum energy density as large as 4.24 J/cm3 was obtained in BT-PS/PS films. [ABSTRACT FROM PUBLISHER]

Compared with the inorganic particles/silicone rubber (IOP/SR) composites filled with single-sized particle solely, the IOP/SR composites cofilled with micro-sized Si3N4 and nano-sized Al2O3 particles show a low relative dielectric permittivity (5.25) and high thermal conductivity (1.62 W m-1K-1), which are a bit higher than the permittivity (4.1) and remarkably larger than the thermal conductivity (0.16 W m-1K-1) of pure SR. Agari model gives a better prediction for these results. The images indicate that the nano-sized Al2O3 particles are closely filled into the gaps between the micro-sized Si3N4 particles and play a role as a bridge-link action to form a continuous thermally conductive network. This also confirms that the loading of the micro-sized Si3N4 particles in the SR composites prepared by the cofilled model contributes a positive thermal conduction and induces the low dielectric permittivity of the IOP/SR composites. [ABSTRACT FROM AUTHOR]

To endow excellent dielectric properties for embedded capacitors application, high-permittivity BaTiO3/polyvinylidene fluoride (BT/PVDF) nanocomposites with sandwich multi-layer structure were fabricated via a spin-coated and hot-molding technique. Dependences of dielectric properties of the BT/PVDF multi-layer nanocomposites on frequency and temperature were studied. Results show that concentration and dispersion of BT particles in multi-layer structure nanocomposites had an obvious influence on the final dielectric permittivity. Influence of the compatibility between adjacent layers on dielectric permittivity was also discussed. We use the effective-medium theory and capacitance series model to predict the theoretical values of the dielectric permittivity of the nanocomposites. [ABSTRACT FROM PUBLISHER]

Theoretical models were used to predict dielectric permittivities of the thermosetting polyimide (PI) matrix nanocomposite films loading with BaTiO3 (BT) nanoparticles prepared by the alkoxide route. The observed dielectric permittivities are in good agreement with calculated values using Jayasundere equation and effective medium theory when the interactions of nanoparticle-nanoparticle and nanoparticle-polymer are considered. Additionally, temperature dependence of dielectric permittivity of the BT/PI nanocomposite films at 103 Hz was also studied for both heating from -50 to 150 °C and cooling from 150 to -50 °C. The transformation in crystal phase of BT and changes of free volume in PI were considered to be the main factors influencing the dielectric permittivities of the BT/PI nanocomposite films. [ABSTRACT FROM AUTHOR]

Effects of inorganic nanoparticles size and thermal agitation on dielectric properties of BaTiO3/poly(vinylidene fluoride) (BT/PVDF) nanocomposite films at low frequency were studied. The dielectric properties of the BT/PVDF nanocomposite films with three kinds of diameters of BT nanoparticles loading at 50 vol. % were studied in a wide frequency range from 10-2 Hz to 107 Hz by two measured processes. A significant low-frequency dielectric permittivity increase and the difference in dielectric properties between two measured processes were discussed. Interfacial polarization, crystal phase effect, and thermal agitation are considered to analyze the significant increase and difference in dielectric behaviors. [ABSTRACT FROM AUTHOR]

Dielectric composite films of the micro-nanosize BaTiO3 (BT) particles embedded into a polyvinylidene fluoride (PVDF) matrix were prepared by using a simple blending and casting processing. Effects of the micro-nanosize cofilled model at different mciro-nanosize volume ratios of BT particles on microstructure and dielectric properties of the composite films were researched. The results show that the nanosize BT particles can be filled into the gaps between the micron-size BT particles so that a tightly stack structure in the BT/PVDF composite film is formed. As a result, the dielectric properties of the composite films with the micro-nanosize BT loading at 40 vol% is higher than these with single nanosize BT loading solely if the interactions between the BT fillers are considered. The maximum values of dielectric permittivity were about 55 because of the superior internal microstructure of composite films when the mciro-nanosize volume ratio of BT particles is close to 1/1. In this case, a remarkable synergistic effect for improving the dielectric properties was also observed. The microstructure and the assumed cofilled model of the composite films would used to explain the experimental results well. [ABSTRACT FROM AUTHOR]

Abstract: There is an increasing need for high-permittivity (high-k) materials due to rapid development of electrical/electronic industry. It is well-known that single composition materials cannot meet the high-k need. The combination of dissimilar materials is expected to be an effective way to fabricate composites with high-k, especial for high-k polymer–matrix composites (PMC). This review paper focuses on the important role and challenges of high-k PMC in new technologies. The use of different materials in the PMC creates interfaces which have a crucial effect on final dielectric properties. Therefore it is necessary to understand dielectric properties and processing need before the high-k PMC can be made and applied commercially. Theoretical models for increasing dielectric permittivity are summarized and are used to explain the behavior of dielectric properties. The effects of fillers, fabrication processes and the nature of the interfaces between fillers and polymers are discussed. Potential applications of high-k PMC are also discussed. [Copyright &y& Elsevier]

For present ceramic particles/polymer dielectric composite materials, their dielectric properties and thermal conductivity haven't met the application requirement at the same time. In this research, to achieve this goal, barium titanate@super short MWCNTs (BT@SSCNT) core-shell particle was prepared in a confinement reactive space built by water phase and oil phase. Polyvinylidene fluoride (PVDF) based composite flexible films reinforced by the BT@SSCNT particles possessed desired dielectric and excellent thermal behaviors. Especially for the composite film with 60 wt% (containing less than 17 wt% SSCNT) loading, at 102 Hz and in the wide temperature range of −40–140 °C, dielectric constant and dielectric loss varied from 476 to 764 and from 2.74 to 4.58, respectively. Meanwhile the thermal conductivity of this film reaches 25.43 W/(m K). The promising dielectric properties and high thermal conductivity of the films are attributed to multiple roles of SSCNT shell layer including external electric field applying on BT particles, tremendous interfacial polarization area, restricted electron motion and electron efficient in transporting heat. The BT@SSCNT/PVDF composite films can be a promising candidate for the modern electronic industry. Image 1 [ABSTRACT FROM AUTHOR]

• Cross-linked PI aerogels inspired by spider web show high elasticity and strength. • Finite element simulation revealed the cause of improved thermal insulation of CPA. • The CNTs/CPA-3 based strain sensors exhibit "synergistically enhanced" sensitivity. • The proposed theoretical model explained the mechanism of action of the sensors. With the development of intelligent electronic power systems, the performance of flexible electronic sensors with portability and miniaturization is increasingly in demand. It is extremely challenging to achieve high modulus and high elasticity of polymer matrix simultaneously due to the inherent strength-elasticity conflict of elastic polymer. Here, a series of "spider-web-like" cross-linked polyimide aerogels (CPAs) had been successfully prepared. Benefiting from the robust dynamic network structure, the CPAs exhibited excellent compressive resilience, tunable dielectric permittivity, high thermal insulation property (λ = 0.040 W/m∙K) and modulus (E = 1073 KPa). Additionally, due to the excellent resilience of the CPAs and tunable permittivity, a CNTs/CPA-3 composite aerogel-based strain sensor obtained by assembling the CPA-3 with carbon nanotubes (CTNs) possessed synergistically enhanced sensitivity, high selectivity and "multi-touch" stress detection, without deterioration even after 2000 cycles. Furthermore, the established mathematical model revealed the internal mechanism of the synergistic enhancement of sensing performance of sensor with strain-controllable permittivity. Thus, the fabricated CPAs might be an ideal substrate material for flexible electronic sensors in electronic power systems, and the mathematical model established could also provide a reliable reference for improving the sensitivity and detection limits of sensors. [ABSTRACT FROM AUTHOR]

There is an urgent need for interlayer dielectric materials with ultralow dielectric properties, high temperature resistance and hydrophobicity in the field of microelectronics due to the development of high-density integration and miniaturization of electronic components. Herein, porous polyimide (PI) films were successfully prepared by using ionic liquid (1-Butyl-3-methylimidazolium tetrafluoroborate, [BMIM][BF 4 ]) as porogen for the first time. Based on the inherent good compatibility between [BMIM][[BF 4 ] and polyimide, this ionic liquid could be uniformly dispersed in the PI matrix, thus creating a favorable prerequisite for the formation of pores. It was demonstrated that the optimized rearrangement of PI molecular chains induced by etching process of [BMIM][BF 4 ] led to the generation of pores and the reduction of chain spacing, which endow the porous films excellent dielectric, thermal and mechanical properties. The film with the porosity ratio of 85 vol% exhibited minimum permittivity of 1.5 at a wide range from 102 to 106 Hz, high temperature of 5% weight loss about 532 °C. The porous PI films not only provide the promising ultralow permittivity dielectric materials for the development of modern integrated circuits, but also present potential application in adsorption separation and special electromagnetic detection. [Display omitted] • [BMIM][BF4] as porogen was introduced into PI, which realized preparation of ultralow-permittivity porous PI films. • The porous PI films exhibited excellent thermal stability, high hydrophobicity and electromagnetic wave absorption. • The preparation process is simple and environment-friendly and porous films present excellent practical application potential. [ABSTRACT FROM AUTHOR]