Fabrication of highly refractive barium‐titanate‐incorporated polyimide nanocomposite films with high permittivity and thermal stability

Crystalline nanoparticles of barium titanate (BT) are incorporated into polyimide (PI) to fabricate highly refractive, anti‐UV‐degradable nanocomposite films with high permittivity and thermal stability. For homogeneous incorporation of BT nanoparticles into the PI matrix, the BT nanoparticles are surface modified by phthalimide with the aid of a silane coupling agent as a scaffold. The PI nanocomposites are prepared by in situ polymerization in which a diphthalic anhydride and a diamine are used to form the PI matrix in the presence of the surface‐modified nanoparticles. The refractive index of the transparent nanocomposite films reaches 1.85 at a nanoparticle content of 59 vol% with a high dielectric constant of ε = 37 and thermal stability up to 460 °C. Copyright © 2012 Society of Chemical Industry     

Fabrication of barium titanate nanoparticles‐polymethylmethacrylate composite films and their dielectric properties

A method for incorporating barium titanate (BT) nanoparticles into polymethylmethacrylate (PMMA) is proposed to prepare composite films with a high dielectric constant and high transparency. BT particles with particle sizes of 7.8–24.0 nm and crystal sizes of 8.60–17.7 nm were synthesized with a complex alkoxide method. Surface of the BT particles was modified with 3‐methacryloxypropyltrimethoxysilane to introduce double bonds that was grafted with PMMA. The PMMA‐grafted BT particles were suspended in PMMA/N‐methyl‐2‐pyrrodinone solution and spin‐coated onto glass substrates to prepare the PMMA/BT composite films. The surface modification gave composite films having smooth surfaces and high transparency. An increase in BT particle size and BT volume fraction in the film tended to increase the dielectric constant while keeping the dissipation factor around 5%. The dielectric constant of the film prepared for a particle size of 24.0 nm at 39 vol% attained a value of 19.8 that was around four times higher than that of the pure PMMA film. The dielectric constants of the BT particles estimated by the application of Lichtenecker's mixing model to the composite films were 75.3, 105.1, and 166.3 for particle sizes of 7.8, 11.0, and 24.0 nm, respectively. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

High‐k dielectric composites of poly(2‐cyanoethyl vinyl ether) and barium titanate for flexible electronics

High‐k dielectric composite material for electronic applications was obtained by mixing a polymer with high dielectric constant, poly(2‐cyanoethyl vinyl ether) (CEPVA), and highly crystalline barium titanate (BT). Barium titanate nanoparticles of a size in the range 40–90 nm were prepared by the solvothermal method. By optimizing the reaction conditions, the formation of carbonate impurities and the agglomeration of formed nanoparticles were significantly reduced compared to state‐of‐the‐art procedures. Dielectric spectroscopy was measured in the range of 0.01 Hz to 10 MHz and showed the dielectric constant to be ?′ ～ 35–40 with only 30 vol % content of BT in the composite. Extrapolating to 100% BT nanoparticle concentration and using the Lichtenecker model, the dielectric constant ?′ = 365 ± 27 at 10 kHz was obtained. The relaxation and electrical properties were investigated in depth, and a new relaxation phenomenon was revealed. CEPVA/BT composite is considered suitable for electronic applications, in which high ?′ together with a good mechanical flexibility are required, such as organic field effect transistors. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45236.     

Reduced sedimentation of barium titanate nanoparticles in poly(vinylidene fluoride) films during solution casting by surface modification

Reduced sedimentation of barium titanate (BaTiO₃, BT) nanoparticles during solution casting to prepare the BT/poly(vinylidene fluoride) (PVDF) films is systematically investigated by surface modification of the BT nanoparticles. The surface of BT nanoparticles is hydroxylated by hydrogen peroxide (H₂O₂) or aminated by γ‐aminopropyl triethoxysilane (γ‐APS). It is found that the compatibility between the fillers and polymer matrix is remarkably improved by such surface treatments. As a result, the agglomeration and sedimentation of BT nanoparticles in the BT/PVDF composite films are significantly reduced, which is supported by morphology observation. Better dielectric properties such as higher dielectric constant, higher breakdown strength, and lower dielectric loss are also obtained for the composite films with surface‐modified fillers than those with raw fillers. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42662.     

High dielectric constant SU8 composite photoresist for embedded capacitors

A novel, photodefinable, high dielectric constant (high‐k) nanocomposite material was developed for embedded capacitor applications. It consists of SU8 as the polymer matrix and barium titanate (BT) nanoparticles as the filler. The UV absorption characteristics of BT nanoparticles were studied with a UV‐Vis spectrophotometer. The effects of BT nanoparticle size, filler loading, and UV irradiation dose on SU8 photopolymerization were systematically investigated. The dielectric properties of the photodefined SU8 nanocomposites were characterized. Embedded capacitors using the novel high dielectric constant SU8 composite photoresist were demonstrated on a flexible polyimide substrate by the UV lithography method. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1523–1528, 2007     

Fabrication of barium titanate nanoparticles‐epoxy resin composite films and their dielectric properties

A method for fabricating epoxy resin films dispersing the surface‐modified barium titanate (BT) particles (BT‐epoxy resin composite films) are proposed. BT particles with a size of 7.8 nm and a crystal size of 8.6 nm were synthesized with a complex alkoxide method. To introduce epoxy groups on the BT particle surface, the BT particles were surface‐modified with 2‐(3,4‐epoxycyclohexyl)‐ethyltrimethoxysilane. A precursor solution, which was prepared by prereacting 2,2‐bis(4‐glycidyloxyphenyl)propane (BGPP) and phthalic anhydride in 4‐butyrolactone and adding the surface‐modified BT particles to the prereacting solution, was spin‐coated on glass substrates to fabricate the composite films. An increase in BT volume fraction in film increased dielectric constant of the composite film while keeping dissipation factor below 0.03. The dielectric constant attained 10.8 at a BT volume fraction of 30% in film that was around twice higher than pure epoxy resin film. POLYM. COMPOS., 31:1179–1183, 2010. © 2009 Society of Plastics Engineers     

Gradient dielectric constant sandwich-structured BaTiO3/PMMA nanocomposites with strengthened energy density and ultralow-energy loss

High energy storage density with low-energy loss polymer films are essential for high-performance electric devices. To avoid the high-energy loss of utilizing nonlinear polymer materials, a sandwich nanostructure comprising a linear polymer poly(methyl methacrylate) (PMMA) matrix embedded with a high dielectric constant BaTiO₃ (BT) interlayer and poly(vinylidene fluoride) (PVDF) binder was constructed using a solution casting strategy. This structural design takes advantage of each component in the composite. The good dispersion of BT particles in the binder, which was incorporated between PMMA, enabled a high dielectric constant and fewer defects. Additionally, the excellent film formation ability of the PVDF binder guarantees the uniform thickness and stable structure of the BT mid-layer, and good miscibility between PVDF and PMMA enhanced the interaction between each layer. Interestingly, since the dielectric constant of PVDF was between BT fillers and PMMA, a dielectric gradient distribution mitigated the local electric field concentration, as proven by the simulation results. Consequently, a low-loss linear PMMA composite film exhibited satisfying breakdown strength and excellent discharged energy density, which were 25% and 460% higher than those of pristine PMMA, respectively.     

Characterization of barium titanate reinforced acrylonitrile butadiene rubber composites for flexible electronic applications: influences of barium titanate content

The aim of this study was to develop high dielectric constant flexible polymers with a highly efficient and cost‐effective approach using acrylonitrile butadiene rubber (NBR) as the polymer matrix and barium titanate (BT) as the high dielectric constant filler. The BT powder was synthesized with a solid‐state reaction and was characterized using a particle size analyzer, XRD, SEM and Fourier transform infrared spectroscopy. NBR/BT composites were fabricated using an internal mixer with various BT loadings up to 160 phr. The influence of BT loading on the cure characteristics and mechanical, dynamic mechanical, thermal, dielectric and morphological properties was determined. The incorporation of BT in the NBR matrix shortened scorch time and increased delta torque. The mechanical properties, thermal stability and dielectric constant were greatly improved and increased with BT loading. The results suggest that the reinforcement effect was achieved due to strong hydrogen bonding or polar–polar interactions between NBR matrix and BT filler. This is further corroborated by the good dispersion of BT filler in the NBR matrix observed with SEM imaging. These findings can be applied to produce high‐performance dielectric elastomers. © 2020 Society of Industrial Chemistry     

Synthesis,characterization, optical,and dielectric properties of polyvinyl chloride/cadmium oxide nanocomposite films

Nano‐sized cadmium oxide (CdO) was synthesized using a sol–gel method and mixed with poly(vinyl chloride) (PVC). X‐ray diffraction and high‐resolution transmission electron microscopy measurements indicated that the average particle size of the CdO is about 70.18 nm. Scanning electron microscopy images revealed a good dispersion of CdO nanoparticles on the surface of the PVC films. The optical energy band gap (E_g) showed a decrease from 5.08 to 4.88 eV with increasing the CdO content. The refractive index dispersion of the nanocomposite films was found to obey the single oscillator model. The dispersion parameters were changed by CdO incorporation. According to the frequency and temperature dependence of the dielectric constant (ε′), the observed α_a‐relaxation peaks were assigned to the micro‐Brownian motion of the polymer main chains. The influence of CdO nanoparticles content on the ac conductivity and the activation energy of PVC nanocomposite films were discussed. It was found that both dielectric and optical properties were reinforced by the adding of CdO nanoparticles to the PVC matrix. Finally, the results of the present system are compared with those of similar materials. POLYM. COMPOS., 35:1842–1851, 2014. © 2014 Society of Plastics Engineers     

Nanocomposites of Surface‐Modified BaTiO3 Nanoparticles Filled Ferroelectric Polymer with Enhanced Energy Density

We report nanocomposites of increased dielectric permittivity, enhanced electric breakdown strength and high‐energy density based on surface‐modified BaTiO₃ (BT) nanoparticles filled poly(vinylidene fluoride) polymer. Polyvinylprrolidone (PVP) is used as the surface modification agent and homogeneous nanocomposite films have been prepared by solution casting processing. The dielectric permittivity of the nanocomposite with treated BT is higher than those with untreated BT and reaches the maximum value of 77 (1 kHz) at BT concentration of 55 vol%. The electric breakdown strength of the nanocomposite is greatly enhanced to 336 MV/m at BT concentration of 10 vol% and the calculated energy density is 6.8 J/cm³. The results indicate that using PVP as surface modification agent can greatly enhance the dielectric permittivity and electric breakdown strength of the ceramic–polymer nanocomposite and achieve high‐energy density for energy storage and power capacitor applications.     

Optical and physical properties of zirconium dioxide reinforced poly(methyl methacrylate) nanocomposite films

The objective of this study was to investigate the fundamental aspects of acrylic resin and zirconia nanoparticle interaction to analyze the optical properties and subsequent changes in refractive index with incremental loading of nanoparticles. Poly(methyl methacrylate) (PMMA) reinforced with zirconia nanoparticles were prepared by dip coating, spin coating and solvent casting techniques. An overall understanding of the polymer nanocomposite film has been achieved using the spectroscopic and morphological studies. The vital aspect of this whole study is to derive a simple yet an efficient nanocomposite film capable of imparting extraordinary optical properties. Within the limitations of this research a very crucial property of the material has been revealed. The RI as well as the optical transparency of the nanocomposite film has been steadily maintained with a significant increase of RI by the magnitude of 0.06 and ~100% light transmittance on incorporation of pure zirconia nanoparticles into PMMA matrix has been achieved. The best technique found was spin coating as it could yield thin films and better transparency and higher refractive index.     

Enhancement of mechanical strength associated with interfacial tension between barium titanate and acrylonitrile–butadiene rubber with different acrylonitrile contents by surface modification

Acrylonitrile–butadiene rubber (NBR) with different acrylonitrile (ACN) contents was filled with barium titanate (BT) to prepare the polymer dielectrics. The neat NBR, NBR/untreated BT, and NBR/bis‐(γ‐triethoxysilylpropyl)‐tetrasulfide (silane coupling agent KH845‐4) modified BT (MBT) composites were prepared. At low ACN content (ACN content 20 wt %), the tensile strength of the NBR/MBT composites increased by 173.6% from 2.69 to 7.36 MPa compared to the neat NBR. The pleasing results were not found in those composites with high ACN content. Both surface modifications of BT and NBR with low ACN content would result in lower interfacial tension between BT and NBR. A strong interfacial adhesion was observed between MBT and NBR with 20 wt % ACN content. The interfacial adhesion had great contribution to the mechanical strength of composites. Moreover, the dielectric properties of composites were also investigated in detail. The addition of BT enhanced the dielectric constant of composites markedly. This study can be applied in manufacturing electronic devices, which are subjected to oily environments for a long time. At the same time, the study can provide some help for researchers to select the polymer matrix and the appropriate surface modification agent of functional filler. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45936.     

The surface modification of BaTiO3 and its effects on the microstructure and electrical properties of BaTiO3/silicone rubber composites

Interfacial interaction and compatibility between the ceramic dielectric and polymer matrix have strong impact on the dielectric constant and dielectric loss of their composites. In this work, the BaTiO₃ (BT) nanoparticles were modified by (1) stearic acid (SA); (2) aluminate coupling agent (ACA); (3) the combination of SA and coupling agent aluminate, and then incorporated them with silicone rubber (SR) matrix to prepare BT/SR nanocomposites. The effects of the surface modification methods of BT on the microstructure and electrical properties of BT/SR nanocomposite films were studied. The results showed that SA and ACA were beneficial to the dispersion of BT and resulted in the strong interfacial interaction. The composite of BT modified by SA not only had high dielectric constant of 10.5, 2 times higher than that of the unmodified BT/SR nanocomposite (4.7), at the same time showed lower dielectric loss. J. VINYL ADDIT. TECHNOL., 24:288–294, 2018. © 2017 Society of Plastics Engineers     

Photocontrol of the refractive index of poly(methyl methacrylate) with a nitrone additive

Hydroxy‐substituted aromatic nitrone derivatives were used for the photochemical control of the refractive index of poly(methyl methacrylate) (PMMA) films. Upon irradiation with 366‐nm light in solution, these derivatives underwent rearrangement reactions, which eventually produced N,N‐diarylformamide derivatives in quantitative yields. Similar photoreactions of the aromatic nitrones in the PMMA films lowered the refractive index of the films by as much as 0.014. The magnitude of the observed refractive‐index change was enough for hydroxy‐substituted nitrones to be used as additives for the fabrication of graded‐index‐type polymer optical fibers. In addition, the refractive index of the PMMA films remained almost constant at any conversion of the starting nitrone derivatives for at least 70 days at room temperature. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2517–2520, 2004     

Core-shell structured BaTiO3@SiO2@PDA for high dielectric property nanocomposites with ultrahigh energy density

Flexible nanocomposite dielectrics with high dielectric constant and discharge energy density have broad application prospects in the field of energy storage. However, dielectrics with high dielectric constant tend to have a high dielectric loss. Herein, we prepared a dielectric composite material with ultra-high discharge energy density by modifying the interface between nanoparticles and poly(vinylidene fluoride-co-hexafluoropropylene) (P[VDF-HFP]). After coating a shell of insulating amorphous SiO₂ (~7 nm) outside the barium titanate (BT), the electric field concentration and current density inside BT particles can be significantly reduced. In addition, coating the SiO₂ shell with a polydopamine (PDA) shell (~7 nm) not only enhances the interface interaction between the nanoparticles and the polymer matrix, but also can form lots of microcapacitors in the composite. As a result, an ultra-high discharge energy density of 13.78 J/cm³ at the expense of relatively inconspicuous efficiency (~59.8%) in the BT@SiO₂@PDA/P (VDF-HFP) with 2.5 wt% loading has been achieved under 460 kV/mm. This is mainly attributed to the increases of dielectric constant from 12.1 to 14.2 and the relatively low dielectric loss (0.086) at 100 Hz. Moreover, compared with the pure P (VDF-HFP) (400 kV/mm), the breakdown voltage of the composite with 2.5 wt% loading is surged to 460 kV/mm, which benefited from the hindrance of nanoparticles on carrier migration at low content. This work has realized a thin-film dielectric with ultra-high discharge energy density through a novel design of the nanoparticle structure, providing a theoretical direction for the development of polymer dielectric capacitors.     

Characterization of antireflective coatings on poly(methyl methacrylate) substrate by different process parameters

The high/low refractive index organic/inorganic antireflective (AR) hybrid polymers were formed using the sol–gel process, in which TiO₂/2‐hydroxyethyl methacrylate (2‐HEMA) (high refractive index hybrid polymer) and SiO₂/2‐HEMA (low refractive index hybrid polymer) two‐layer thin films were formed on a hard coating deposited poly(methyl methacrylate) (HC‐PMMA) substrate by both spin coating and dip coating. The relationship between the process parameters and the optical properties, thickness, porosity, surface morphology, and adhesion was determined. The results show that the reflectance of the two‐layer thin films on HC‐PMMA substrate is less than 0.21% (λ = 550 nm), with good adhesion (5B) and a hardness of up to 4H. In addition, the thickness, porosity, and roughness of the films affect refractive index and the antireflection properties of the AR two‐layered thin film. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Surface‐modified silica nanoparticles for reinforcement of PMMA

Polymethyl methacrylate (PMMA) was introduced onto the surface of silica nanoparticles by particle pretreatment using silane coupling agent (γ‐methacryloxypropyl trimethoxy silane, KH570) followed by solution polymerization. The modified silica nanoparticles were characterized by Fourier‐transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). Sedimentation tests and lipophilic degree (LD) measurements were also performed to observe the compatibility between the modified silica nanoparticles and organic solvents. Thereafter, the PMMA slices reinforced by silica‐nanoparticle were prepared by in situ bulk polymerization using modified silica nanoparticles accompanied with an initiator. The resultant polymers were characterized by UV–vis, Sclerometer, differential scanning calorimetry (DSC). The mechanical properties of the hybrid materials were measured. The results showed that the glass transition temperature, surface hardness, flexural strength as well as impact strength of the silica‐nanoparticle reinforced PMMA slices were improved. Moreover, the tensile properties of PMMA films doped with silica nanoparticles via solution blending were enhanced. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Enhancement of dielectric constants of epoxy thermosets via a fine dispersion of barium titanate nanoparticles

In this study, we examined a facile approach for achieving a fine dispersion of barium titanate (BT) nanoparticles (NPs) in epoxy thermosets. First, the surfaces of BT NPs were modified with poly(ε‐caprolactone) (PCL) via a surface‐initiated ring‐opening polymerization approach. We found that the PCL‐grafted BT NPs were easily dispersed in epoxy thermosets. The fine dispersion of the PCL‐grafted BT NPs in the epoxy thermosets was evidenced by transmission electron microscopy and dynamic mechanical thermal analysis. We found that the organic–inorganic nanocomposites displayed significantly enhanced dielectric constants and low dielectric loss compared to the control epoxy. The nanocomposites containing 14.1 wt % BT NPs possessed dielectric constants as high as at a frequency of 10³ Hz. The dielectric loss was measured to be 0.002 at a frequency of 10³ Hz. The improved dielectric properties are accounted for the fine dispersion of the BT NPs in the epoxy thermosets. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43322.     

Role of ceramic reinforcement in composite polymer electrolyte

Composite polymer electrolytes were prepared from PEO (polyethylene oxide), lithium perchlorate (LiClO₄), and with three different dielectric reinforcements such as lead zirconium titanate (PZT)‐12000, barium titanate (BT)‐1000, and Alumina (Al₂O₃)‐6. Differential scanning calorimetry and X‐ray diffractometry were employed to reveal the crystalline nature of the electrolytes. The conductivity of the composite polymer electrolytes were measured by impedance spectrometry. Among the three systems, PZT reinforced composite exhibits maximum ionic conductivity of 2.9 × 10⁻⁵ S/cm at room temperature. The ionic conductivity of the polymer composites increases with increase in dielectric constant of the reinforcement. The composite with alumina reinforcement displayed strongly modified properties with very weak temperature dependence of conductivity. POLYM. COMPOS., 36:42–46, 2015. © 2014 Society of Plastics Engineers     

Preparation and characterization of TiO2 and polymer nanocomposite films with high refractive index

Novel nanocomposite films of TiO₂ nanoparticles and hydrophobic polymers having polar groups, poly (bisphenol‐A and epichlorohydrin) or copolymer of styrene and maleic anhydride, with high refractive indices, high transparency, no color, solvent‐resistance, good thermal stability, and mechanical properties were prepared by incorporating surface‐modified TiO₂ nanoparticles into polymer matrices. In the process of preparing colloidal solution of TiO₂ nanoparticles, severe aggregation of particles can be reduced by surface modification using carboxylic acids and long‐chain alkyl amines. These TiO₂ nanoparticles dispersed in solvents were found not to aggregate after mixing with polymer solutions. Transparent colorless free‐standing films were obtained by drying a mixture of TiO₂ nanoparticles colloidal solution and polymer solutions in vacuum. Transmission electronic microscopic studies of the films suggest that the TiO₂ nanoparticles of 3–6 nm in diameter were dispersed in polymer matrices while maintaining their original size. Thermogravimetric analysis results indicate that the nanocomposite film has good thermal stability and the weight fraction of observed TiO₂ nanoparticles in the film is in good accordance with that of theoretical calculations. The refractive index of nanocomposite films of TiO₂ and poly(bisphenol‐A and epichlorohydrin) was in the range of 1.58–1.81 at 589 nm, which linearly increased with the content of TiO₂ nanoparticles from 0 to 80 wt %. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007