Effects of ultrasonic assisted processing and clay nanofiller on dielectric properties and lithium ion transport mechanism of poly(methyl methacrylate) based plasticized polymer electrolytes

Lithium ion conducting solid polymer electrolyte (SPE) films consisted of poly(methyl methacrylate) (PMMA) matrix with lithium perchlorate as a dopant ionic salt, poly(ethylene glycol) as plasticizer and montmorillonite clay as inorganic nanofiller have been prepared by classical solution casting and high intensity ultrasonic assisted solution casting methods. The X‐ray diffraction study confirmed the amorphous structure of all these PMMA‐based solid electrolytes and the clay nanosheets existed in exfoliated form in their amorphous phase. Dielectric relaxation spectroscopy had been employed for the investigation of complex dielectric function, ac electrical conductivity, electric modulus, and impedance spectra of these electrolytes over the frequency range from 20 Hz to 1 MHz. It was observed that the dielectric properties and ionic conductivity of the electrolytes strongly depended on the sample preparation methods, and also had changes with addition of the clay nanofiller. Temperature‐dependent dielectric study of the electrolyte films confirmed that their dc ionic conductivity and conductivity relaxation time values obeyed the Arrhenius behavior. This study also revealed that the lithium ion transportation in the ion–dipolar complexes of these electrolytes occurred through hopping mechanism and it was correlated with the conductivity relaxation time. Preparation of these electrolyte films through ultrasonic assisted solution casting method increased the ionic conductivity by more than one order of magnitude in comparison to that of the classical solution casting method, which revealed that the former was a novel method for the preparation of these SPEs of relatively enhanced ionic conductivity. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42188.     

Structural and AC impedance studies on nanocomposite polymer electrolytes based on poly(ε‐caprolactone)

Nanocomposite polymer electrolyte (NCPE) films of [75 wt % poly(ε‐caprolactone) : 25 wt % zinc triflate] + x wt % nanofiller Al₂O₃ (x = 1, 3, 5, 7) were prepared by solution cast technique. Such NCPE films were characterized using Fourier transform infrared and AC impedance spectroscopic techniques. Complexation of polymer with salt and nanofiller was revealed from FTIR analysis. On the other hand, an apparent increase in the number density of charge carriers upto 5 wt % loading of the nanofiller was also confirmed. Furthermore, AC impedance spectroscopic studies have shown that ionic conductivity increases with the addition of Al₂O₃ and reaches a maximum of 2.5 × 10^?5 S cm^?1 at room temperature for 5 wt % loading of nanofiller. The dielectric behavior of all the synthesized samples has also been analyzed and presented. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40524.     

Effects of solution mixing temperature on dielectric properties of PMMA/Pristine bentonite nanocomposites

We examined the effects of mixing temperature on the dielectric properties of polymethylmethacrylate (PMMA)‐pristine bentonite nanocomposites by using X‐ray diffraction, FT‐IR and dielectric spectroscopies. The samples were prepared during 8 hours at temperatures 265 K, 273 K, 281 K, 289 K and 298 K without any intercalative agent and the PMMA to pristine bentonite weight ratio was chosen as 1 : 10. It was observed that with decreasing the mixing temperatures, the permittivity decreases and the dielectric relaxation displaces towards the lower frequencies with the decrease of mixing temperatures. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39907.     

Synthesis and dielectric properties of polystyrene‐clay nanocomposite materials

Polystyrene‐clay nanocomposite (PsCN) materials were synthesized and their properties of crystallinity, thermal behavior, and dielectric characteristics were investigated. A polymerizable cationic surfactant, [2‐(dimethylamino)ethyl]triphenylphonium bromide, was used for the intercalation of montmorillonite (MMT). The organophilic MMT was prepared by Na⁺‐exchanged MMT and ammonium cations of a cationic surfactant in an aqueous medium. Organophilic styrene monomers were intercalated into the interlayer regions of organophilic clay hosts followed by a free‐radical polymerization. Exfoliation to 2 wt % MMT in the polystyrene (PS) matrix was achieved as revealed by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Thermal properties by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were also studied. The dielectric properties of PsCNs in the form of film with clay loading from 1.0 to 5.0 wt % were measured under frequencies of 100 Hz–1 MHz at 25–70°C. A decreased dielectric constant and low dielectric loss were observed for PsCN materials. The dielectric response at low frequency that originated from dipole orientation was suppressed due to the intercalation of clay materials. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1368–1373, 2004     

Ion‐transport study in nanocomposite solid polymer electrolytes based on chitosan: Electrical and dielectric analysis

In this study, (1.1111 ? x)(0.9CS–0.1NaTf)? xAl₂O₃(0.02 ≤ x ≤ 0.1) [where CS is chitosan, NaTf is sodium triflate (NaCF₃SO₃), and Al₂O₃ is aluminum oxide] nanocomposite solid polymer electrolyte (SPE) films based on CS were prepared by a solution casting technique. X‐ray diffraction and scanning electron microscopy analysis revealed that the alumina nanoparticles had a great effect on the structural and morphological behavior of the CS–NaTf (90:10) polymer electrolyte. An investigation of the electrical and dielectric parameters of the nanocomposite SPE films was conducted. Electrical impedance spectroscopy was carried out for this purpose. The relationships between the electrical and dielectric parameters were used to interpret and understand the ion‐conduction mechanism. We observed that the direct‐current conductivity (σ_dc) and dielectric constant followed the same trend with salt concentration. σ_dc versus temperature showed the Arrhenius and Vogel‐Fulcher‐Tammann (VTF) regions. The drops of σ_dc at high temperatures were observed for all of the samples. The ion relaxation dynamics were studied from Argand plots. For the first time, we confirmed the existence of a strong experimental relationship between the high‐frequency semicircle of the impedance plots and the high‐frequency dispersion regions of the alternating‐current conductivity (σ_ac). The dispersion regions of σ_ac were used to study the ion‐conduction mechanism. The behavior of the frequency exponent as a function of the temperature was used to interpret σ_dc versus the temperature. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41774.     

Spectroscopic and electrochemical studies on block‐polymer/PMMA blend based composite polymer electrolytes

Poly(methylmethacrylate)(PMMA)/oxymethylene‐linked polyoxyethylene multi‐block polymer(Om‐POE_n, where n represents number of unit  CH₂CH₂O ) blend based composite electrolyte films containing different lithium salt concentration and nanofillers' content are prepared using solvent evaporation technique. The interaction of polymer–salt complex has been confirmed using FTIR spectral studies. The figuration of CPE was studied by XRD. Ionic conductivity and thermal behavior of the CPEs were studied with various salt concentrations, temperature, and nanofillers' content. The surface structure of the CPE is also investigated using scanning electron microscopy. The high room temperature ionic conductivity, transmittivity in the visible region, and thermal stability make these CPEs potential candidates as solid‐like electrolytes for electrochemical devices. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Enhanced mechanical strength and conductivity of PVFM based membrane and its supporting polymer electrolytes

Polyvinyl formal based polymer electrolyte membranes are prepared via the optimized phase inversion method with poly(ethylene oxide) (PEO) blending. The physical properties of blend membranes and the electrochemical properties of corresponding gel polymer electrolytes (GPEs) are characterized by field emission scanning electron microscopy, X‐ray diffraction, differential scanning calorimetry, mechanical strength test, electrolyte uptake test, AC impedance spectroscopy, cyclic voltammetry, and galvanostatic charge–discharge test. The comparative study shows that the appearance of PEO obviously enhances the tensile strength of membranes and the ionic conductivity of corresponding GPEs. When the weight ratio of PEO is 30%, the tensile strength of membrane achieves 12.81 MPa, and its GPE shows high ionic conductivity of 2.20 × 10⁻³ S cm⁻¹, wide electrochemical stable window of 1.9–5.7 V (vs. Li/Li⁺), and good compatibility with LiFePO₄ electrode. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41839.     

Electrospun nanofiber‐coated separator membranes for lithium‐ion rechargeable batteries

Nanofiber‐coated composite membranes were prepared by electrospinning polyvinylidene fluoride‐co‐chlorotrifluoroethylene (PVDF‐co‐CTFE) and PVDF‐co‐CTFE/polyvinylidene fluoride‐co‐hexafluoropropylene (PVDF‐co‐HFP) onto six different Celgard® microporous battery separator membranes. Application of a PVDF‐based copolymer nanofiber coating onto the surface of the battery separator membrane provides a method for improving the electrolyte absorption of the separator and the separator‐electrode adhesion. Peel tests showed that both PVDF‐co‐CTFE and PVDF‐co‐CTFE/PVDF‐co‐HFP nanofiber coatings have comparable adhesion to the membrane substrates. Electrolyte uptake capacity was investigated by soaking the nanofiber‐coated membranes in a liquid electrolyte solution. PVDF‐co‐CTFE and PVDF‐co‐CTFE/PVDF‐co‐HFP nanofiber‐coated membranes exhibited higher electrolyte uptake capacities than uncoated membranes. It was also found that PVDF‐co‐CTFE nanofiber‐coated membranes have higher electrolyte uptakes than PVDF‐co‐CTFE/PVDF‐co‐HFP nanofiber‐coated membranes due to the smaller diameters of PVDF‐co‐CTFE nanofibers and higher polarity of PVDF‐co‐CTFE. The separator–electrode adhesion properties were also investigated. Results showed PVDF‐co‐CTFE and PVDF‐co‐CTFE/PVDF‐co‐HFP nanofiber coatings improved the adhesion of all six membrane substrates to the electrode. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Melt‐intercalation nanocomposites with fluorinated polymers and a correlation for nanocomposite formation

Various fluorinated polymers were investigated to produce polymer nanocomposites with special clays. Natural and organically treated montmorillonite clays were melt‐compounded with the polymers. Characterization by wide‐angle X‐ray scattering and transmission electron microscopy showed the separation of montmorillonite layers and the formation of polymer nanocomposites. Organically treated montmorillonite clay dispersed in poly(vinylidene fluoride) and various vinylidene fluoride copolymers and formed nanocomposites. Natural and organophilic clays were not well dispersed in other fluorinated copolymers and polyethylene. A correlation was developed for the formation of polymer–clay nanocomposite structures in chlorinated and fluorinated polymers in terms of the dielectric constant. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1061–1071, 2004     

Investigation of improved dielectric and thermal properties of ternary nanocomposite PMMA/MXene/ZnO fabricated by in-situ bulk polymerization

Electric power system applications demand for high-temperature dielectric materials. The improved performance of polymer nanocomposites requires improvement in their thermal conductivity & stability, dielectric stability and processing technique. However, they often lose their dielectric properties with a rise in temperature. Here, we offer a solution by incorporating electrically conducting material (MXene) and semiconducting inorganic nanoparticles (ZnO NPs) into an insulating PMMA polymer matrix to maintain high dielectric constant, both at the room and high temperature. Therefore, to achieve desirable thermal and dielectric properties is the main objective of the present study based on the homogeneous distribution of the nanofillers by in-situ bulk polymerization assisted by strong sonication in the corresponding polymer. The introduction of MXene and ZnO NPs into the PMMA not only acquires a substantial increment in the dielectric constant, to attain a value 437, with minimum energy loss of 0.36 at 25 Hz, but also improves the thermal conductivity of PMMA up to 14 times by causing the reduction of thermal resistance, which is actually responsible for the poor thermal conductivity of amorphous pure PMMA polymer. More importantly, hybrid PMMA/4:2 wt% MXene:ZnO nanocomposite leads to an excellent thermal stability. Moreover, further characterization of the synthesized nanocomposites by FTIR, SEM and XRD leads to the evaluation of strong interaction of ternary components with PMMA matrix.     

Significant decreased dielectric constant and loss of polystyrene–clay nanocomposite materials by using long‐chain intercalation agent

Polystyrene–clay nanocomposite (PsCN) materials have been prepared by a free radical polymerization process. Montmorillonite (MMT), modified by two different organics, was investigated: one contains a short chain and three benzyl groups on the ammonium ion (DAETPB), while the other contains a long chain (HTAC). The organic modification determines the extent of exfoliation or intercalation of the materials. Exfoliation is more likely to occur using HTAC, as then the gallery of clay has been opened more due to the long chain structure. Exfoliation of MMT in polystyrene (PS) matrix was revealed by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were employed to confirm the increased thermal stability of these PsCN materials. Dielectric properties of polystyrene‐clay nanocomposites, in the form of film with clay loading from 1.0 to 5.0 wt %, were measured under frequencies of 100 Hz～1 MHz at 25～70°C. Decreased dielectric constant and low dielectric loss were observed for PsCN materials. Especially, the decrease of dielectric constant was found to be related to the extent of exfoliation of clay. It is recognized that the confinement effect of clay results in the suppression of the dielectric response of the nanocomposite materials at low frequency. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2402–2410, 2004     

Synthesis and proton conductivity studies of methacrylate/methacrylamide‐based azole functional novel polymer electrolytes

Anhydrous polymer electrolytes based on azole functional methacrylates and methacrylamides have been produced for use in proton exchange membrane fuel cells (PEMFCs). Poly(methacryloyl chloride) (PMAC) was prepared first by free‐radical polymerization of methacryloyl chloride, followed by side chain functionalization with 5‐aminotetrazole (ATet), 3‐amino‐1,2,4‐triazole (ATri) and 1H‐1,2,4‐triazole (Tri). Finally, the obtained polymers were doped with triflic acid (TA) at stoichometric ratios of 1.0, 2.0 and 4.0 with respect to azole units, and the anhydrous polymer electrolytes were obtained. The membranes were characterized by FT‐IR, ¹³C‐NMR, and elemental analysis. Thermal behaviour of polymers was explored by TGA and DSC. The samples were thermally stable up to approximately 200 ^oC. Proton conductivity was measured by impedance spectroscopy. Trifilic acid doped poly(methacryloyl aminotetrazole) (PMAATet‐(TA)₄), poly(methacryloyl‐3‐amino‐1,2,4‐triazole) (PMA‐Tri‐(TA)₄), and poly(methacryloyl‐1,2,4‐triazole) (PMA‐ATri‐(TA)₄) showed maximum proton conductivities of 0.01 Scm^?1, 0.02 Scm^?1 and 8.7x10^?4 Scm^?1, respectively, at 150^°C and anhydrous conditions. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39915.     

Chitosan‐based gel film electrolytes containing ionic liquid and lithium salt for energy storage applications

Fabrication, characterization, and a comparative study have been performed for chitosan‐based polymer electrolytes using two different dispersion media. Chitosan gel film (solid) electrolytes are fabricated using acetic acid or adipic acid as the dispersant for chitosan in combination with ionic liquid and lithium salt. This quaternary system of chitosan, acetic acid or adipic acid, 1‐butyl‐3‐methylimadazolium tetrafluoroborate (ionic liquid), and lithium chloride is formed as an electrolyte for potential secondary energy storage applications. The ionic conductivities, thermal, structural, and morphological properties for these electrolytes are compared. The ionic conductivities for chitosan/adipic acid (CHAD) and for chitosan/acetic acid (CHAC) systems are in the range of 3.71 × 10⁻⁴−4.6 × 10⁻³ and 1.3 × 10⁻⁴ −3.2 × 10⁻³ S cm⁻¹, respectively. The thermal stability of CHAD‐based electrolytes is determined to be higher than that of CHAC‐based electrolytes. Preliminary studies are performed to determine the electrochemical stability of these materials as solid film electrolytes for electrochemical supercapacitors. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42143.     

Natural rubber/poly(ethylene‐co‐vinyl acetate)‐blend‐based nanocomposites

Natural rubber (NR)/poly(ethylene‐co‐vinyl acetate) (EVA) blend–clay nanocomposites were prepared and characterized. The blend nanocomposites were prepared through the melt mixing of NR/EVA in a ratio of 40/60 with various amounts of organoclay with an internal mixer followed by compression molding. X‐ray diffraction patterns revealed that the nanocomposites formed were intercalated. The formation of the intercalated nanocomposites was also indicated by transmission electron microscopy. Scanning electron microscopy, used to study the fractured surface morphology, showed that the distribution of the organoclay in the polymer matrix was homogeneous. The tensile modulus of the nanocomposites increased with an increase in the organoclay content. However, an increase in the organoclay content up to 5 phr did not affect the tensile strength, but the organoclay reduced this property when it was increased further. This study also indicated that a low silicate content dispersed in the blend matrix was capable of increasing the storage modulus of the material. The addition of the organoclay also increased the decomposition temperature of the NR/EVA blends. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 353–362, 2006     

Zinc ion conducting blended polymer electrolytes based on room temperature ionic liquid and ceramic filler

Zinc ion conducting nanocomposite gel polymer electrolytes (NCGPEs) comprising of poly(vinyl chloride) (PVC)/poly(ethyl methacrylate) (PEMA) blend, zinc triflate [Zn(OTf)₂] salt, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIMTFSI) ionic liquid (IL) and fumed silica (SiO₂) viz. [PVC/PEMA–Zn(OTf)₂–EMIMTFSI–SiO₂] exhibited the highest ionic conductivity value of 6.71 × 10⁻⁴ Scm⁻¹ at room temperature. The ion–filler–polymer interactions and probable conformational changes observed in the structure of the gel composites due to the entrapment of IL and dispersion of nano-sized SiO₂ were confirmed from X-ray diffraction (XRD) and Attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy. Scanning electron microscopic (SEM) images of NCGPEs demonstrated uniform surface with abundant interconnected micropores. The cationic transport number of NCGPE samples has been found to be appreciably enhanced up to a maximum of 0.69 thus demonstrating a considerable improvement in Zn²⁺ ion conductivity. The NCGPE film possesses an electrochemical stability window up to 5.07 V (vs. Zn/Zn²⁺) and ensures feasible zinc stripping/plating in the redox process. The addition of SiO₂ into the gel polymer electrolyte system has effectively reduced the glass-transition temperature (T_g) of the NCGPE films and also accomplished improved thermal stability up to approximately 180 °C which were ascertained from Differential scanning calorimetry (DSC) and Thermogravimetric (TG) results. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47654.     

Enhanced dielectric properties of poly(vinylidene fluoride)–surface functionalized BiFeO3 composites using sodium dodecyl sulfate as a modulating agent for device applications

In this work, we prepared a series of poly(vinylidene fluoride) (PVDF)–surface functionalized BiFeO₃ (h‐BFO)–Sodium dodecyl sulfate (SDS) composite films by solvent casting method to investigate the effect of SDS in the composites. The X‐ray diffraction confirmed that the structure of h‐BFO significantly changed in the PVDF‐(h‐BFO)‐SDS composite in comparison with the rhombohedral structure of pure BiFeO₃. The microscopic study illustrated that the composite with a higher percentage of SDS content facilitated the dispersion as well as proper distribution of ceramic particles in the polymer matrix. The presence of different functionalities of respective polymer and the modified fillers was confirmed by FTIR Spectrophotometer. The dielectric and electrical study done by Impedance Analyzer revealed that the SDS treated surface functionalized composites showed relatively higher dielectric properties than that of two phase composites and pure polymer. Finally, the ferroelectric properties of the composite films done by P‐E loop tracer revealed that the SDS‐treated composites showed an enhanced remanent polarization. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45040.     

Highly selective sulfonated poly(vinylidene fluoride‐co‐hexafluoropropylene)/poly(ether sulfone) blend proton exchange membranes for direct methanol fuel cells

Proton exchange membranes (PEMs) based on blends of poly(ether sulfone) (PES) and sulfonated poly(vinylidene fluoride‐co‐hexafluoropropylene) (sPVdF‐co‐HFP) were prepared successfully. Fabricated blend membranes showed favorable PEM characteristics such as reduced methanol permeability, high selectivity, and improved mechanical integrity. Additionally, these membranes afford comparable proton conductivity, good oxidative stability, moderate ion exchange capacity, and reasonable water uptake. To appraise PEM performance, blend membranes were characterized using techniques such as Fourier transform infrared spectroscopy, AC impedance spectroscopy; atomic force microscopy, and thermogravimetry. Addition of hydrophobic PES confines the swelling of the PEM and increases the ultimate tensile strength of the membrane. Proton conductivities of the blend membranes are about 10^?3 S cm^?1. Methanol permeability of 1.22 × 10^?7cm² s^?1 exhibited by the sPVdF‐co‐HFP/PES10 blend membrane is much lower than that of Nafion‐117. AFM studies divulged that the sPVdF‐co‐HFP/PES blend membranes have nodule like structure, which confirms the presence of hydrophilic domain. The observed results demonstrated that the sPVdF‐co‐HFP/PES blend membranes have promise for possible usage as a PEM in direct methanol fuel cells. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43907.     

Characterization of nanoclay intercalation during foaming with in situ energy‐dispersive X‐ray diffraction

The effect of the foaming process on the intercalation of nanoclays in low‐density polyethylene–nanoclay nanocomposites was studied with in situ energy‐dispersive X‐ray diffraction (ED‐XRD) with synchrotron radiation as an X‐ray source. The solid nanocomposites containing different amounts of an organomodified montmorillonite were melt‐blended with blowing agents of different nature and later foamed by heating at atmospheric pressure. During the foaming process, ED‐XRD experiments were performed. These experiments allowed us to measure the time evolution of the interlamellar distance of the clay platelets during the melting and foaming of the nanocomposites; we obtained information about the evolution of the clay structure during the process. The experimental results show that the foaming process induced the intercalation of the clays independently of the blowing agent used. We also proved that the degree of intercalation depended on the expansion ratio reached and that the intercalation produced was larger when the blowing agent was azodicarbonamide. For this particular blowing agent, some interesting effects appeared; these included a catalytic effect of the clays on the decomposition temperature, a partial intercalation of the clays during melt blending, and a very stable structure of the clay particles after foaming. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43432.     

Anomalous behavior of the dielectric and electrical properties of polymeric nanodielectric poly(vinyl alcohol)–titanium dioxide films

The complex dielectric permittivity, alternating‐current electrical conductivity, electric modulus, and impedance spectra of polymeric nanocomposite (PNC) films consisting of a poly(vinyl alcohol) (PVA) matrix dispersed with nanosize particles of titanium dioxide (TiO₂); (i.e., PVA–x wt % TiO₂, where x is 0, 1, 3, or 5) were investigated in the frequency range 20 Hz to 1 MHz at ambient temperature. A detailed analysis of the results showed that the values of the dielectric and electrical parameters of these PNC‐based nanodielectric films varied anomalously with increasing TiO₂ concentration. The temperature‐dependent dielectric characterization of the PVA–3 wt % TiO₂ film revealed that the dielectric polarization at a fixed frequency increased nonlinearly with increasing temperature. The temperature‐dependent electric modulus relaxation time values of the nanodielectric film obeyed Arrhenius behavior. The X‐ray diffraction study confirmed that the crystalline phase of the PVA matrix decreased with increasing TiO₂ concentration; this suggested that the interaction of the TiO₂ nanoparticles caused some destruction of the hydroxyl group dipolar ordering in the hydrogen‐bonded crystalline structure of the pristine PVA matrix. The intensities of the diffraction peaks of the TiO₂ nanofiller were enhanced as its concentration increased in these nanodielectrics; this confirmed the existence of TiO₂ nanoparticles inside the crystalline phases of the PVA matrix. The surface morphology of the films was examined by the study of their scanning electron micrographs. The feasibility of using these flexible polymeric nanodielectric films as electrical insulators and dielectric substrates in low‐power microelectronic devices operated at audio‐ and radio‐frequency electric fields was explored. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44568.     

Polyacrylonitrile‐based proton conducting membranes containing sulfonic acid and tetrazole moieties

Proton conducting membranes based on polymers containing sulfonic acid and tetrazole moieties were developed. Successful syntheses of poly(acrylonitrile‐co ‐styrene sulfonic acid) (PAN‐co ‐PSSA), poly(acrylonitrile‐co ‐5‐vinyl tetrazole) (PAN‐co ‐PVTz), and poly(acrylonitrile‐co ‐5‐vinyl tetrazole‐co ‐styrene sulfonic acid) (PAN‐co ‐PVTz‐co ‐PSSA) were confirmed by ¹H‐nuclear magnetic resonance spectroscopy, elemental analysis, and Fourier transform infrared spectroscopy. Two approaches were performed to study the effects of molar ratio of sulfonic acid to tetrazole and tetrazole content on membrane properties. In the first approach, PAN‐co ‐PSSA was blended with PAN‐co ‐PVTz at three molar ratios. The second approach focused on PAN‐co ‐PVTz‐co ‐PSSA membranes with various tetrazole contents. PAN‐co ‐PSSA membrane was also prepared. All solution‐cast membranes were hydrolytically stable, except for PAN‐co ‐PVTz‐co ‐PSSA with 71% tetrazole. Surface morphologies of blend membranes were studied using scanning electron microscopy, and no phase separation was observed. Water uptake was shown to increase with increasing tetrazole. All membranes exhibited high thermal stability (up to 250 °C) and high storage moduli. Proton conductivity was found to depend significantly on relative humidity. The influences of sulfonic acid to tetrazole ratio and tetrazole content on proton conduction were observed and discussed. A maximum proton conductivity of 7.1 × 10^?3 S/cm at 26 °C was obtained from PAN‐co ‐PSSA membrane. In addition, all tested membranes showed relatively good oxidative stability after treatment in Fenton's reagent. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45411.