Dielectric Properties Of Poly Research Articles

Dielectric and mechanical properties of poly(butylene succinate) thin film composites incorporated with barium strontium titanate powder

ABSTRACTHigh dielectric constant barium strontium titanate (Ba0.7Sr0.3TiO3 or BST) powder was prepared by sol-gel method for using as a filler in poly(butylene succinate) (PBS) composite with 0–3 connectivity system. Moreover, thermal and dielectric properties of poly(butylene succinate) integrated with BST powder were studied. The results showed the success of improving thermal stability and dielectric constant of poly(butylene-succinate) by increasing amount of BST powder. Therefore, the prepared PBS-BST composite thin films with good dielectric properties, flexibility, and processability could be applicable for the thin film capacitor for high-frequency electronic devices.

Synthesis, thermal degradation and dielectric properties of poly[2-hydroxy,3-(1-naphthyloxy)propyl methacrylate

2-Hydroxy-3-(1-naphthyloxy)propyl methacrylate (NOPMA) monomer was synthesized from reaction of 2-[(2-naphthyloxy)methyl]oxirane with methacrylic acid in the presence of pyridine. The polymerization of NOPMA was carried out by free radical polymerization method in the presence of AIBN at 60 °C. The structure of monomer and polymer was characterized by 1H-NMR, 13C-NMR and FT-IR spectroscopy techniques. The glass transition temperature and average-molecular weights of poly(NOPMA) were measured using differential scanning calorimetry and gel permeation chromatography, respectively. The thermal degradation behavior of poly(NOPMA) has been investigated by FT-IR studies of the partially degraded polymer and thermogravimetry. The cold ring fractions (CRFs) were collected at two different temperatures, initially fraction-1 (CRF1) is from room temperature to 320 °C, and the other fraction-2 (CRF2) is from 320 to 500 °C. The volatile products of the degradation were trapped at −195 °C (in liquid nitrogen). All the fractions were characterized by FT-IR, 1H and 13C-NMR spectroscopic techniques, and the cold ring fractions (CRFs) were also characterized by GC–MS. For the degradation of polymer, the major compound between products of CRFs is α-naphthol. The GC–MS, FT-IR and NMR data showed that depolymerization corresponding to monomer was not prominent below 320 °C in the thermal degradation of poly(NOPMA). The mode of thermal degradation containing formation of the major products was identified. The dielectric permittivity (ε′), the loss factor (ε″) and conductivity (σac) were measured using a dielectric analyzer in the frequency range of 50 Hz to 20 kHz.

Improving dielectric properties of polyarylene ether nitrile with conducting polyaniline

In this study, the dielectric properties of poly(arylene ether nitrile) (PEN) were effectively improved by the incorporation of conducting polyaniline (PANI). Sulfuric acid doped PANI was prepared and incorporated into the PEN matrix as additives by using the solution-casting method. The micro-morphologies, mechanical, thermal and dielectric properties of the obtained PANI/PEN nanocomposites were investigated in detail. SEM observation showed that the PANI phase is homogeneously dispersed in the PEN matrix. The obtained PANI/PEN nanocomposites showed good thermal stability as the glass transition temperatures and initial decomposition temperatures of them are higher than 190 and 270 °C. The dielectric constant of the composites was significantly improved after the introduction of PANI, and the dielectric constant of the composite PANI/PEN100 reaches 23.5 (250 Hz), with an increment of 650 % when 10 wt% of PANI is introduced. The temperature dependencies of dielectric constant measurement showed that the dielectric constant of the PANI/PEN composites is stable before 180 °C and these composites can be long-term used at high temperature for their good reversibility and robustness during the heating and cooling scans. These PANI/PEN composites will be a potential candidate as high performance electronic devices materials used at high temperature.

Effect of chemical and physical doping with iodine on the optical and dielectric properties of poly(vinyl chloride)

Iodination of poly(vinyl chloride) (PVC) was prepared by addition of I2 or I− through physical adsorption and chemical modification techniques forming (PVC–I2) (composite I) and (PVC–I−) (composite II), respectively.Investigations were performed using TGA, DSC, FTIR, UV–vis absorbance analyses and ac conductivity measurements. The activation energy of decomposition, ΔEd, was found to be 215.15kJ/mole and 43.1kJ/mole for PVC and composite II, respectively. Both direct and indirect optical transitions near the absorption edge are observed. Addition of I2 or I− decreases the optical energy gap for PVC. The chemical replacement of Cl− ion in PVC matrix with I− ion in composite II increases the electrical conductivity by two orders. A possible conduction mechanisms are suggested.

Influence of preparation conditions on structural and dielectric properties of PVDF–MoS2 nanotubes composite films

Poly(vinylidene fluoride) composite films with MoS2 nanotubes were prepared from solutions using the doctor blade method and dried under various temperatures. While FTIR-ATR and Raman spectroscopy have revealed that composite films dried at room temperature are homogeneous and crystallize mainly in the γ-phase, a decrease in porosity upon addition of MoS2 has been observed using scanning electron microscopy. Dielectric investigations revealed (i) a decrease from e’ ∼ 7 in pure polymer to e’ ∼ 4 in composite with 1 wt% of MoS2, and (ii) a slight increase in e’ and σ’ values upon further addition of MoS2. Films dried at 110 °C were heterogeneous and FTIR-ATR has shown an increase in α-phase content upon addition of 1 wt% of MoS2. In this case, high values of e’ ∼ 10 that increased slightly upon increasing amount of MoS2 in the film have been measured. By showing a direct relation between structure and dielectric response, it is suggested that the dielectric properties of poly(vinylidene fluoride)–MoS2 nanotubes composites can be tailored by changing the preparation conditions.

Morphological Study and Dielectric Behavior of Nonisothermally Crystallized Poly(ethylene naphthalate) Nanocomposites as a Function of Graphene Content

Morphological evolution and dielectric properties of poly(ethylene naphthalate)- (PEN-) graphene nanocomposites nonisothermally crystallized have been investigated. PEN-graphene nanocomposites containing 0.01, 0.025, 0.05, 0.075, and 0.1 wt% of graphene were prepared by melt blending in a mini twin screw extruder. The results showed that graphene exhibited a superior influence on morphological and conformational structure of PEN during nonisothermal crystallization at low graphene contents. Crystallization temperature (Tc) was found to be increased up to 18°C supporting the high nucleating activity of graphene layers. Wide angle X-ray diffraction (WAXD) and Fourier Transform Infrared Spectroscopy (FTIR) indicated that graphene modifies the conformation of PEN chains promoting crystallinity and favoring the evolution fromαtoβcrystalline form with homogeneous lamellar thickness. It may be attributed to the structural similarity between naphthalene rings and graphene structure and toπ-πinteractions during nucleation. Dielectric behavior was found to be a function of graphene content where the nanocomposites changed from dielectric to low conducting material when passing from 0.075 to 0.1 wt% of graphene content. This phenomenon permits having a wide range of properties to fit a wide variety of applications required to store electrical energy of low voltage.

The chain conformation, relaxation dynamics and thermodynamics of poly(acrylamide- co -diallyldimethylammonium chloride) solution: Dielectric analysis coupled with scaling approach

Abstract Dielectric properties of poly(acrylamide-co-diallyldimethylammonium chloride) (P(AAm-co-DADMAC)) aqueous solution have been measured as a function of concentration and temperature over a frequency range from 40 Hz to 110 MHz, respectively. Different from the dielectric behavior of homopolymers solutions (only one dielectric relaxation was observed in poly(diallyldimethylammonium chloride) (PDADMAC) solution around MHz, and no detectable dielectric relaxation is observed in polyacrylamide (PAAm) homopolymer solution), two dielectric relaxations are observed in P(AAm-co-DADMAC) solution around 700 kHz and MHz, and they are named low- and high-frequency relaxation, respectively. The relaxation parameters (dielectric increment and relaxation time, obtained by fitting the dielectric spectra with the Cole–Cole equation) of these two relaxations show scaling relations with the copolymer concentration. The information about the dynamics of copolymer solution are got from the discussion of the mechanisms of these two relaxations in light of the scaling theory: the low- and high-frequency relaxations are ascribed to the fluctuation of condensed and free counterions, respectively; the fluctuation ranges of these two kinds counterions reveal the different chain conformations exist in the copolymer solution. For the dependence of dielectric relaxation on temperature in P(AAm-co-DADMAC) solution, the thermodynamic parameters, activation enthalpies and entropies, of these two relaxations are calculated from the relaxation time by means of the Eyring equation. The temperature dependences of dielectric increments are also discussed. The comparison about the concentration and temperature dependences of dielectric properties between P(AAm-co-DADMAC) and PDADMAC solution are discussed from the perspective of the difference of molecular structure in the proper place of the text.

Solution Casting Behavior and Dielectric Properties of Poly(vinylidene fluoride) (PVDF)/Barium Titanate (BaTiO<SUB>3</SUB>) Nanocomposites with High Dielectric Constant

Solution Casting Behavior and Dielectric Properties of Poly(vinylidene fluoride) (PVDF)/Barium Titanate (BaTiO<SUB>3</SUB>) Nanocomposites with High Dielectric Constant

Electrical and dielectric properties of poly(1,3,4-oxdiazole) nanocomposite films with graphene sheets dispersed in layers

Electrical and dielectric measurements over a broad frequency range from 20 Hz to 2 MHz were carried out for a series of sulfonated poly(1,3,4-oxadiazole) (sPOD) nanocomposite films containing exfoliated graphene sheets of 0.1-10.0 wt%, which were manufactured via ultrasonication-based solution mixing and casting method. TEM and XRD data revealed that the graphene sheets were dispersed by forming a layered structure in the nanocomposite films with >2.0 wt% graphene. The frequency-dependent electrical conductivity and relative permittivity of the nanocomposite films were dependent on the graphene content. The neat sPOD and its nanocomposites with lower graphene contents of 0.1-2.0 wt% exhibited low electrical conductivity of ~10-13-10-12 S/cm and relative permittivity of 1.7-6.6 at 20 Hz. In cases of the nanocomposite films with high graphene contents of 5.0 and 10.0 wt%, highly improved relative permittivity of ~101 and ~560 at 20 Hz as well as electrical conductivity of ~10-9 S/cm and ~10-6 S/cm was attained at 20 Hz, respectively. In addition, the nanocomposite films with 5.0 and 10.0 wt% exhibited relatively high capacitance of ~39.7 pF and ~75.5 pF at 20 Hz, respectively. The highly enhanced relative permittivity and capacitance for the nanocomposite films with 5.0-10.0 wt% graphene was interpreted to be owing to the accumulation of electronic charges at the interfaces between insulating sPOD matrix and conductive graphene sheets dispersed in layers.

Peculiar dielectric properties of poly(diphenylene phthalide) at elevated temperatures

We report on the results of analysis of dielectric properties of poly(diphenylene phthalide) in the frequency range from 25 Hz to 1 MHz at temperatures of 373 and 653 K. It is found that at T 423 K, the value of e″ sharply increases with temperature, attaining a value of about 40 at T = 653 K. We believe that this increase in e″ is due to an increase in the concentration of electrons appearing in poly(diphenylene phthalide) due to thermionic emission. The height of the potential barrier at the aluminum cathode-poly(diphenylene phthalide) interface controlling the ternionic current is estimated as ∼0.7 eV.

Imaging the effects of annealing on the polymorphic phases of poly(vinylidene fluoride).

The effect of annealing on the phase transformation and the dielectric properties of poly(vinylidene fluoride) (PVDF) is explored using quasi-single molecule (quasi-SM) microscopy. The solvatochromic properties of nile red (NR) are employed to measure the spatial distribution of the local dielectric constant (ε) in ∼30 μm thick PVDF films before and after annealing at 90 °C. The results presented here demonstrate that nonannealed films exhibit much larger ε distributions, both in terms of magnitude and distribution, when compared to annealed films. The polymorphic phase of PVDF before and after annealing is also confirmed using X-ray diffraction. Nonannealed films are found to be in the γ-phase with annealing promoting the transition to primarily β-phase. Combining these results, we conclude that the decrease in ε with annealing time is due to the phase transformation from γ- to β-phase. Using quasi-SM imaging techniques one can readily visualize the ε environments present within different polymorphic phases of PVDF.

Improving dielectric properties of poly(vinylidene fluoride) composites: effects of surface functionalization of exfoliated graphene

To investigate the effects of surface functionalization of exfoliated graphene (EG) on the crystalline form of β-phase and dielectric properties of poly(vinylidene fluoride) (PVDF), we prepared PVDF-based composites reinforced by different functionalized EG. The X-ray photoelectron spectroscopy results indicated that a wide variety of chemical functional groups such as C–OH, C–O–C, C=O, COOH and C–F could be introduced on the surface of modified EG. As confirmed by results of Fourier transform infrared spectrum and X-ray diffraction, the β-phase PVDF can be produced in the composites with the incorporation of functionalized EG. In the frequency ranging from 102 to 107 Hz, the dielectric permittivity of PVDF composites shows an obvious increase owing to a variation of the carbonyl group (C=O) content. Among all the composites, the EG grafted with polymethyl methacrylate/PVDF composite has the highest dielectric permittivity and dielectric loss.

Spectroscopic and dielectric study of iodine chloride doped PVA/PVP blend

Optical and dielectric properties of Poly (vinyl alcohol)/ Poly (vinyl pyrrolidone) blend and blend loaded with different concentrations of ICl2 were studied. UV–Vis spectral analysis before and after γ-irradiation suggested that the addition of iodine led to complete complexation between ICl2 and polymer blend were observed. The values of optical parameters λo, So and n∞ were determined from by reflection and transmission spectra in the range of 200–800 nm. The refractive index was found to change non-monotonically with the increase of iodine. Infrared analysis revealed the formation of new species between blend and iodine content. There were some changes in IR absorption bands, position and their intensities. The AC conductivity (σac) behavior of all prepared films was investigated in the frequency range 42 Hz–5 MHz and under different isothermal stabilization in the temperature range 300–400 K. The dependence of the imaginary modulus (M″) on frequency at lower frequencies was estimated. The increasing values of M″ may be attributed to the bulk effect with the increase in temperature.

Effect of incorporating aromatic and chiral groups on the dielectric properties of poly(dimethyltin esters).

High-dielectric constant materials are critical for numerous applications such as photovoltaics, photonics, transistors, and capacitors. There are numerous polymers used as dielectric layers in these applications but can suffer from having a low dielectric constant, small band gap, or ferroelectricity. Here, the structure-property relationship of various poly(dimethyltin esters) is described that look to enhance the dipolar and atomic polarization component of the dielectric constant. These polymers are also modeled using first principles calculations based on density functional theory (DFT) to predict such values as the total, electronic, and ionic dielectric constant as well as structure. A strong correlation is achieved between the theoretical and experimental values with the polymers exhibiting dielectric constants >4.5 with dissipation on the order of 10(-3) -10(-2) .

Enhanced permittivity and energy density in neat poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) terpolymer films through control of morphology.

Polymer materials with large dielectric constants are desirable for the development of high energy density capacitors. We show that the dielectric properties of poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) [P(VDF-TrFE-CTFE)] can be improved by the use of processing conditions that favor formation of a highly crystalline morphology of the nonpolar α-phase. Through the use of spin coating, thermal treatment above the melting temperature, and quenching, we were able to attain a highly crystalline, α-phase rich morphology that has a quite large dielectric constant of 77 ± 10 at 1 kHz. The final morphology and phase composition of the terpolymer films depend strongly on the postprocessing thermal treatment and the quality of the solvent. Evaluation of the polarization behavior of the terpolymer films as a function of electric field reveal that the polymer exhibits a relaxor-ferroelectric behavior and has a substantial energy density of 9.7 J/cm(3) at fields of up to approximately 470 V/μm. Under millisecond pulsed charge-discharge measurements a 3-fold increase in energy density (27 J/cm(3)) is obtained at high fields (∼600 V/μm). Our study demonstrates that the processing conditions and morphology of fluorinated terpolymer films are controlling factors for achievement of high dielectric permittivity and energy density that are critical for high performance capacitors.

Dielectric properties of poly(vinylidene fluoride) composites based on Bucky gels of carbon nanotubes with ionic liquids

“Bucky gels” of carbon nanotubes were successfully prepared by grinding multi‐walled carbon nanotubes (MWNTs) and ionic liquids (ILs) for several hours. A series of poly(vinylidene fluoride) (PVDF) composites with Bucky gels was obtained through simple melt compounding. The Raman spectrum showed significant interaction among the ILs, MWNTs, and PVDF. The dielectric behavior of the PVDF composites based on unmodified and IL‐modified MWNTs was studied from 40 Hz to 30 MHz. The addition of ILs significantly enhanced the dielectric property of the PVDF/IL/MWNT ternary composites, which was much higher than that of the sum of PVDF/IL and PVDF/MWNT binary composites. The SEM results revealed that both MWNTs and ILs uniformly dispersed throughout the PVDF/IL/MWNT composites because of the strong interaction between them. The DSC and XRD results showed that the addition of ILs in the composites changed the crystallinity and crystal form of the PVDF. POLYM. COMPOS., 36:94–101, 2015. © 2014 Society of Plastics Engineers

Dielectric properties of poly(vinylidene fluoride) nanocomposites filled with surface coated BaTiO3 by SnO2 nanodots

SnO2 nanoparticles with an average diameter of about 4 nm were coated on the surface of BaTiO3 (BT) (∼100 nm) by chemical treatment. With the introduction of BT@SnO2, the dielectric permittivity of poly(vinylidene fluoride) (PVDF) composite was significantly increased to 90 at 103 Hz, which is ∼40% higher than that of the BT/PVDF composites. It was attributed to the enhanced interfacial polarization in the interlayers between BT and PVDF due to the addition of SnO2 nanodots. The distance of SnO2 nanodots on the adjacent BT surfaces is close enough for the electron transport in the matrix by tunneling effect. Besides, the semiconductive SnO2 leads to the weak insulating-conducting transition close to the percolation threshold.

Effect of electron irradiation on electroactive phase and dielectric properties of PVDF films

The effect of electron irradiation on the crystal structure and dielectric properties of poly(vinylidene fluoride) (PVDF) films was investigated. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) were employed to examine the degree of participation in PVDF and the relative fraction of electroactive phase as well as the thermal property of PVDF films. The results showed that both the exothermal peak temperature and the crystallinity of the irradiated film decreased with increasing doses. Huge damage on the morphology of spherulite was observed in irradiated films by atomic force microscopy (AFM). The results of fine structures in PVDF films characterized by X-ray absorption near edge structure (XANES) implied that the dominance of the oxidation reaction occurred during irradiation, and further induced destruction of the regular packed structure. The results indicate that the β-phase exhibits good anti-irradiation ability during the electron irradiation on PVDF film. Because a large portion of the electroactive phase is maintained and intermediate phases are produced in the irradiated PVDF sample, the irradiated film exhibits a relatively high dielectric constant (around 7.8 under 2200 kGy) with low loss.

Preparation and dielectric properties of poly(ε‐caprolactone) compounded with “bucky gels”‐like mixture

AbstractPoly(ε‐caprolactone) (PCL) was melt compounded with “Bucky gels”‐like mixture that prepared by grinding multiwalled carbon nanotubes (MWNTs) and ionic liquids (ILs). Raman spectrum showed the significant interaction between ILs and MWNTs. The dielectric behavior of PCL nanocomposites based on unmodified and IL‐modified MWNTs was studied from 40 Hz to 30 MHz. The addition of ILs significantly enhanced the dielectric property of PCL/IL/MWNT ternary nanocomposites, which was much higher than that of the sum of PCL/IL with PCL/MWNT binary nanocomposites. The dielectric properties of PCL/IL/MWNT nanocomposites were mainly influenced by ILs in low frequency and were dominated by MWNTs in high frequency. SEM results revealed that a more uniform and fine dispersion of MWNTs were achieved throughout the PCL matrix because of ILs. The addition of ILs in nanocomposites changed the crystallinity of PCL. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40231.

Dynamic Mechanical and Dielectric Properties of Poly(vinylidene fluoride) and Epoxidized Natural Rubber Blends

The blending of semi-crystalline polymer, poly (vinylidene fluoride), (PVDF) and uncross-linked elastomer epoxidized natural rubber with 50 mol% epoxide (ENR-50) blends were prepared in an internal mixer by melt mixing process. Dynamic mechanical analysis (DMA) and dielectric analysis (DEA) of PVDF/ENR-50 blends were investigated. It was found that the pure PVDF showed higher storage modulus than that of the pure ENR-50 and storage modulus of the PVDF/ENR blends decrease with increasing ENR-50 content. Furthermore, PVDF showed two relaxation peaks correspond to αa-relaxation and αc-relaxation, while ENR-50 showed only a single relaxation that is related to α-relaxation or glass transition temperature (Tg). Two relaxation peaks were observed in the PVDF/ENR-50 blends due to phase separation. However, the maximum peak of relaxation shifted toward to higher and lower temperature compared with the pure components which indicates the partial miscible blends. Moreover, at high temperature, the neat polymer and blends showed a sharp increase of loss factor (ε) that correspond to conductivity and/or Maxwell-Wagner-Sillar (MWS) process.