Effect of Lithium Perchlorate on the Optoelectrical and Thermal Properties of Poly(Vinylpyrrolidone)/Nano-Cesium Aluminate Solid Polymer Electrolytes

Solid polymer electrolyte (SPE) of polyvinylpyrrolidone (PVP) with varying amounts, namely, 5, 10, and 15?wt% of lithium perchlorate (LiClO₄) as an electrolyte and 8?wt% cesium aluminum oxide (CsAlO₂) nanoparticle have been fabricated by solution intercalation technique. The optoelectrical behaviors of the SPE films have been evaluated using UV–visible spectroscopy. The UV–visible spectral studies revealed the UV light-absorbing nature of NC films with considerable visible transparency. The chemical structure and morphological behaviors of PVP/8?wt% of CsAlO₂–LiClO₄ SPE films have been established by Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy, respectively. The AC conductivity of the SPEs was evaluated at room temperature by digital LCR meter in the frequency range 100 Hz–5?MHz. The thermal behaviors such as T_g and degradation patterns of the SPEs have been evaluated using differential scanning calorimetric analysis and thermogravimetric analysis, respectively.     

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.     

Effect of ethylene carbonate on properties of PVP-CsAlO2-LiClO4 solid polymer electrolytes

ABSTRACT

Solid polymer electrolytes (SPEs) have been widely studied due to its extensive applications in high energy rechargeable batteries, supercapacitors, fuel cells, photoelectrochemical and electrochromic displays. Herein, SPEs based on polyvinyl pyrrolidone (PVP) doped with cesium aluminate (CsAlO₂) nanoparticles (NPs), lithium perchlorate (LiClO₄) as an electrolyte and varying amounts viz., 2, 4, 6 and 8 wt.% of ethylene carbonate (EC) as plasticizer have been fabricated by solution intercalation technique. The structural features of PVP-CsAlO₂-LiClO₄-EC SPEs have been studied by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The morphology of PVP-CsAlO₂-LiClO₄-EC SPEs has been examined by scanning electron microscopy (SEM). The thermal properties of the SPEs were characterized by the thermogravimetric analyzer (TGA) and differential scanning calorimeter (DSC) techniques. The TGA and DSC results revealed that a significant reduction in thermal stability and glass transition temperature (T_g) of PVP with an increase in EC content in SPE films. The optoelectrical properties of PVP-CsAlO₂-LiClO₄-EC SPE films have been evaluated using UV–visible spectroscopy. The band gap energy (E_g) was found to decrease with an increase in EC content, exhibiting a minimum of 4.23 eV for PVP-8 wt.% CsAlO₂-15 wt.% LiClO₄-8 wt.% EC. This could be ascribed to the formation of localized states and increased degree of disorder in the PVP-CsAlO₂-LiClO₄ SPE films. The integrated plasticizers increase the values of refractive index (RI), optical conductivity, and dielectric constants of PVP-CsAlO₂-LiClO₄ SPE films. The AC conductivity of the SPEs has been evaluated at room temperature using digital LCR meter in the frequency range 100 Hz – 5 MHz. The conductivity strongly depends on CsAlO₂ NPs and EC plasticizer content in SPEs.     

Thermal,thermomechanical, and electrochemical characterization of the organic–inorganic hybrids poly(ethylene oxide) (PEO)–silica and PEO–silica–LiClO4

To study the effect of the silica content on the properties of the salt‐free and salt‐added hybrids based on poly(ethylene oxide) (PEO) and silica, two series of hybrids, PEO–silica and PEO–silica–LiClO₄ (O:Li, 9:1) hybrids were prepared via the in situ acid‐catalyzed sol–gel reactions of the precursors [i.e., PEO functionalized with triethoxysilane and tetraethyl orthosilicate (TEOS)]. The morphology of the hybrids was examined by scanning electron microscopy (SEM) of the fracture surfaces of the hybrid. The results indicated that the discontinuity develops with increasing the weight percent of silica in both hybrids. The differential scanning calorimetric (DSC) analysis indicated that effects of silica content on the glass transition temperatures (T_g) of the PEO phase were different in salt‐free and salt‐added hybrids. The T_g of PEO phase increased with increasing weight percent of silica in salt‐free hybrids, whereas the curve of T_g of PEO phase and silica content had a maximum at 35 wt % of silica content in salt‐added hybrids. For both salt‐free and salt‐added hybrids, peaks of the loss tangent, determined by dynamic mechanical analysis (DMA) were gradually broadened and lowered with increasing weight percent of silica. The storage modulus, E′, in the region above T_g increases with increasing silica content for both PEO–silica and PEO–silica–LiClO₄ hybrids. In the conductivity and composition curves for PEO–silica–LiClO₄ hybrids, the conductivity shows a maximum value of 3.7 × 10^?6 S/cm, corresponding to the sample with a 35 wt % of silica. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2471–2479, 2001     

Impact of nano-perovskite La2CuO4 on dc-conduction,opto-electrical sensing and thermal behavior of PVA nanocomposite films

ABSTRACT

Nanocomposite (NC) films of poly vinyl alcohol (PVA) incorporated with varying amounts of perovskite lanthanum cuprate (La₂CuO₄) nanoparticles (NPs) have been fabricated by solution intercalation technique. TEM result showed the size of NPs between 91-134nm. The effects of NPs content on structural and morphological behaviors of PVA have been established by XRD, FTIR and SEM methods. Electrical properties of NC films were performed using LCR-meter. Current (I)–voltage (V) data displayed dc-conductivity increased with increasing NPs content and trends of I–V indicate the dominant Ohmic behavior at voltage <5V and above that Poole–Frenkel emission is the dominant conduction mechanism. Ac-conductivity increases with increase in frequency and dosage of NPs. The maximum ac-conductivity obtained in this investigation is 2.43X10^?5S/cm for PVA/2wt% La₂CuO₄ with lowest activation energy of 0.147 eV at 25^°C. Cyclic voltammetry (CV) revealed the specific capacitance of PVA-NC improved compared to pristine PVA. The reduction in T_g with increment NPs contents was observed. The optical behaviors of NCs were deduced by UV-visible spectroscopy where the result showed band gap energy was reduced from 5.23eV to 3.25eV whereas refractive index increased from 1.71 to 2.44 for pure PVA and PVA/2wt%La₂CuO₄, respectively.     

Fumed SiO2 nanoparticle reinforced biopolymer blend nanocomposites with high dielectric constant and low dielectric loss for flexible organic electronics

In the present study, fumed silica (SiO₂) nanoparticle reinforced poly(vinyl alcohol) (PVA) and poly(vinylpyrrolidone) (PVP) blend nanocomposite films were prepared via a simple solution‐blending technique. Fourier transform infrared spectroscopy (FTIR), ultraviolet–visible spectroscopy (UV–vis), X‐ray diffraction (XRD), and scanning electron microscopy (SEM) were employed to elucidate the successful incorporation of SiO₂ nanoparticles in the PVA/PVP blend matrix. A thermogravimetric analyzer was used to evaluate the thermal stability of the nanocomposites. The dielectric properties such as dielectric constant (?) and dielectric loss (tan δ) of the PVA/PVP/SiO₂ nanocomposite films were evaluated in the broadband frequency range of 10^?2 Hz to 20 MHz and for temperatures in the range 40–150 °C. The FTIR and UV–vis spectroscopy results implied the presence of hydrogen bonding interaction between SiO₂ and the PVA/PVP blend matrix. The XRD and SEM results revealed that SiO₂ nanoparticles were uniformly dispersed in the PVA/PVP blend matrix. The dielectric property analysis revealed that the dielectric constant values of the nanocomposites are higher than those of PVA/PVP blends. The maximum dielectric constant and the dielectric loss were 125 (10^?2 Hz, 150 °C) and 1.1 (10^?2 Hz, 70 °C), respectively, for PVA/PVP/SiO₂ nanocomposites with 25 wt % SiO₂ content. These results enable the preparation of dielectric nanocomposites using a facile solution‐casting method that exhibit the desirable dielectric performance for flexible organic electronics. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44427.     

Effect of nano‐silica on the mechanical,thermal, and crystalline properties of poly(vinyl alcohol)/nano‐silica films

Poly(vinyl alcohol)/nano‐silica (PVA/nano‐SiO₂) films were prepared through extrusion blowing with the addition of water and glycerin as plasticizer. The characteristic properties of PVA/nano‐SiO₂ films were investigated by differential scanning calorimetry, dynamic mechanical analysis, Haake torque rheometry, and atomic force microscopy (AFM). The results showed that the mechanical properties of PVA/nano‐SiO₂ were improved dramatically. The tensile strength of the nanofilms increased from 62 MPa to 104 MPa with loading 0.3 wt % nano‐SiO₂ and the tear strength was improved from 222 KN/m to 580 KN/m. The crystallinity of the films loaded with 0.4 wt. % nano‐SiO₂ decreased from 32.2% to 21.0% and the AFM images indicated that the amorphous region of nanofilms increased with increasing nano‐SiO₂ content. The storage modulus and loss modulus increased to two and nearly three times with 0.3 wt % nano‐SiO₂ loading. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Thermal,mechanical, and surface characterization of starch–poly(vinyl alcohol) blends and borax‐crosslinked films

Starch–poly(vinyl alcohol) (PVA) blends with different compositions were prepared and crosslinked with borax by in situ and posttreatment methods. Various amounts of glycerol and poly(ethylene glycol) with a molecular weight of 400 were added to the formulations as plasticizers. The pure starch–PVA blends and the crosslinked blends were subjected to differential scanning calorimetry, thermogravimetry, and X‐ray photoelectron spectroscopic studies. Broido and Coats–Redfern equations were used to calculate the thermal decomposition kinetic parameters. The tensile strengths and elongation percentages of the films were also evaluated. The results suggested that the glass‐transition temperature (T_g) and the melting temperature strongly depended on the plasticizer concentration. The enthalpy relaxation phenomenon was dependent on the starch content in the pure blend. The crosslinked films showed higher stability and lower T_g's than pure PVA and starch–PVA blends, respectively. High‐resolution X‐ray photoelectron spectroscopy provided a method of differentiating the presence of various carbons associated with different environments in the films. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1313–1322, 2005     

Effect of microstructure on the dielectric properties of poly(vinyl alcohol)–poly(3,4‐ethylenedioxythiophene) doped with poly(styrenesulfonate) composite films

Poly(3,4‐ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT–PSS) was blended with poly(vinyl alcohol) (PVA) to form 0, 10, 20, 30, 40, and 50 vol % PEDOT–PSS/PVA solutions, and their freestanding films were prepared with a simple and cost‐effective solution casting technique at 27 °C in the absence of additives. Field emission scanning electron microscopy images revealed changes in the cocontinuous network to a rodlike morphology in the composite films from 10 to 50 vol % PEDOT–PSS/PVA. The alternating‐current conductivity was found to obey Jonscher's power law. The obtained values of the dielectric constant at 27 °C were relatively high, and a maximum value of 6.7 × 10⁴ at 100 Hz for 40 vol % PEDOT–PSS'/PVA was observed. The dielectric loss attained a maximum value of about 10⁶ at 100 Hz for 40 vol % PEDOT–PSS/PVA. However, a decrease in the dielectric parameters was observed at 50 vol % PEDOT–PSS/PVA because of locally induced strain in the microstructure. The variations in polarization with respect to the applied electric field (P–E) were determined for 50, 100, and 500 Hz at 500 V for the freestanding composite films of lower concentrations up to 20 vol % PEDOT–PSS/PVA. In summary, the dielectric and P–E measurements confirmed that the electrical characteristics changed in accordance to the contribution from both resistive and capacitive sites in the PEDOT–PSS/PVA composites. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45079.     

Dielectric properties of lithium‐perchlorate‐filled acrylonitrile–hexyl methacrylate copolymer films

A series of poly(acrylonitrile‐co‐hexyl methacrylate), PAN‐co‐PHMA, copolymers with various hexyl methacrylate (HMA) contents were synthesized by emulsion technique. The incorporation of HMA units into the copolymers was confirmed by Fourier transform infrared and proton nuclear magnetic resonance (¹H‐NMR) spectroscopy. Glass transition temperatures (T _g) and thermal decomposition temperatures of copolymers were determined by differential scanning calorimetry and thermogravimetric analysis. The T _g of copolymers were lowered monotonically by increasing HMA content, while thermal stabilities of copolymers were enhanced. The frequency dependence of dielectric properties of three different amounts of LiClO₄ salt doped copolymer films was investigated. The influence of molar fraction of HMA on dielectric constant and ac‐conductivity of copolymer films was examined. Samples with higher HMA contents showed better stability and conductivity, as a result of increase in free volume and the mobility of the dipoles. The ac conductivity of copolymers was also improved by increasing LiClO₄ salt which was due to the existence of more charge carriers. PAN(88)‐co‐PHMA(12) copolymer with 1.5 mol% of lithium salt exhibited ionic conductivity of the 7.8 × 10⁻⁴ S/cm at 298 K. POLYM. COMPOS., 38:1792–1799, 2017. © 2015 Society of Plastics Engineers     

Effect of the grain size of nanoparticle dye‐coated titanium dioxide on the short‐circuit current density and open‐circuit voltage of an indium tin oxide/titanium dioxide/poly(acrylonitrile)–propylene carbonate–lithium perchlorate/graphite solar cell

A dye‐sensitized indium tin oxide (ITO)/titanium dioxide (TiO₂)/polyacrylonitrile (PAN)–propylene carbonate (PC)–lithium perchlorate (LiClO₄)/graphite solar cell was fabricated, and its performance was tested in the dark and under the illumination of a 100 mW/cm² light. Three TiO₂ samples were used in the device, namely, uncoated TiO₂, a TiO₂ film coated with methyl red dye, and a TiO₂ film coated with coumarin dye. The films were deposited onto an ITO‐covered glass substrate by a controlled hydrolysis technique assisted with a spin‐coating technique. The films were characterized by scanning electron microscopy to determine their average grain size. The smallest grain size (48 nm) was obtained for the uncoated film. An electrolyte of PAN–LiClO₄ with PC plasticizer was prepared by a solution‐casting technique. A graphite electrode was prepared on a glass slide by an electron‐beam evaporation technique. The device showed rectification properties in the dark and showed a photovoltaic effect under illumination. The device with the uncoated TiO₂ film showed the highest short‐circuit current density (2.0 μA/cm²) and an open‐circuit voltage of 0.64 V because it possessed the smallest grain size. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis,characterization, and properties of flexible magnetic nanocomposites of cobalt ferrite–polybenzoxazine–linear low‐density polyethylene

A simple method for the preparation of magnetic nanocomposites consisting of cobalt ferrite (CF; CoFe₂O₄) nanoparticles, polybenzoxazine (PB), linear low‐density polyethylene (LLDPE), and linear low‐density polyethylene‐g‐maleic anhydride (LgM) is described. The composites were prepared by the formation of benzoxazine (BA)–CF nanopowders followed by melt blending with LLDPE and the thermal curing of BA. The composites were characterized by X‐ray diffraction, thermogravimetric analysis, differential scanning calorimetry, scanning electron microscopy, universal testing machine measurement, and vibrating sample magnetometry. The composites consisting of LLDPE, PB, and LgM (47.5L–47.5PB–5LgM) exhibited a higher tensile strength (23.82 MPa) than pure LLDPE and a greater elongation at break (6.11%) than pure PB. The tensile strength of the composites decreased from 19.92 to 18.55 MPa with increasing CF loading (from 14.25 to 33.25 wt %). The saturation magnetization of the composites containing 33.25 wt % CF was 18.28 emu/g, and it decreased with decreasing amount of CF in the composite. The composite films exhibited mechanical flexibility and magnetic properties. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Novel low‐dielectric‐constant copolyimide thin films composed with SiO2 hollow spheres

A series of copolyimide/SiO₂ hollow sphere thin films were prepared successfully based on bis[3,5‐dimethyl‐4‐(4‐aminophenoxy)phenyl]methane and 9,9‐bis(4‐(4‐aminophenoxy)phenyl)fluorene (molar ratio = 3 : 1) as diamine, and 4,4′‐(4,4′‐isopropylidenediphenoxy)bis(phthalic anhydride) as dianhydride, with different wt % SiO₂ hollow sphere powder with particle size 500 nm. Some films possessed excellent dielectric properties, with ultralow dielectric constants of 1.8 at 1 MHz. The structures and properties of the thin films were measured with Fourier transform infrared spectra, scanning electron microscope, thermogravimetric analysis, and dynamic mechanical thermal analysis. The polyimide (PI) films exhibited glass‐transition temperatures in the range of 209– 273°C and possessed initial thermal decomposition temperature reaching up to 413–477°C in air and 418–472°C in nitrogen. Meanwhile, the composite films were also exhibited good mechanical properties. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Morphological,infrared, and ionic conductivity studies of poly(ethylene oxide)–49% poly(methyl methacrylate) grafted natural rubber–lithium perchlorate salt based solid polymer electrolytes

The potential of poly(ethylene oxide) (PEO) and 49% poly(methyl methacrylate) grafted natural rubber (MG49) as a polymer host in solid polymer electrolytes (SPE) was explored for electrochemical applications. PEO–MG49 SPEs with various weight percentages of lithium perchlorate salt (LiClO₄) was prepared with the solution casting technique. Characterization by scanning electron microscopy, Fourier transform infrared spectroscopy, and impedance spectroscopy was done to investigate the effect of LiClO₄ on the morphological properties, chemical interaction, and ionic conductivity behavior of PEO–MG49. Scanning electron microscopy analysis showed that the surface morphology of the sample underwent a change from rough to smooth with the addition of lithium salts. Infrared analysis showed that the interaction occurred in the polymer host between the oxygen atom from the ether group (C? O? C) and the Li⁺ cation from doping salts. The ionic conductivity value increased with the addition of salts because of the increase in charge carrier up to the optimum value. The highest ionic conductivity obtained was 8.0 × 10^?6 S/cm at 15 wt % LiClO₄. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synergistic enhancement of mechanical,crystalline and dielectric properties of polyarylene ether nitrile‐based nanocomposites by unidirectional hot stretching–quenching

Copper tetra‐amine phthalocyanine (NH₂‐CuPc) was grafted onto barium titanate (BaTiO₃) whose surface was modified by carboxylic polyarylene ether nitrile (CPEN) to afford a nano‐filler (CPEN‐f‐BaTiO₃@NH₂‐CuPc). Through a solution‐casting method combined with ultrasonic dispersion technology, the obtained CPEN‐f‐BaTiO₃@NH₂‐CuPc was successfully incorporated into biphenyl polyarylene ether nitrile (BP‐PEN) matrix to prepare nanocomposite films with various mass fractions of CPEN‐f‐BaTiO₃@NH₂‐CuPc (0, 2.0, 5.0, 10.0 and 20.0 wt%). After that, the nanocomposite films were unidirectionally stretched with various stretching ratios at 280 °C. All the nanocomposite films show excellent mechanical and thermal stability, which is provided by the BP‐PEN matrix. The crystallinity and mechanical, thermal and dielectric properties of the nanocomposite films are efficiently enhanced after the unidirectional hot‐stretching process. The results show that hot‐stretching is a useful method for improving the mechanical and crystallization behaviors as well as the thermal and dielectric properties of the nanocomposite films. © 2017 Society of Chemical Industry     

Solid polymer electrolyte based on waterborne polyurethane for all‐solid‐state lithium ion batteries

A series of solid polymer electrolytes (SPEs) based on comb‐like nonionic waterborne polyurethane (NWPU) and LiClO₄ are fabricated via a solvent free process. The NWPU‐based SPEs have sufficient mechanical strength which is beneficial to their dimensional stability. Differential scanning calorimetry analysis indicates that the phase separation occurs by the addition of the lithium salt. Scanning electron microscopy and X‐ray diffraction analyses illustrate the good compatibility between LiClO₄ and NWPU. Fourier transform infrared study reveals the complicated interactions among lithium ions with the amide, carbonyl and ether groups in such SPEs. AC impedance spectroscopy shows the conductivity of the SPEs exhibiting a linear Arrhenius relationship with temperature. The ionic conductivity of the SPE with the mass content of 15% LiClO₄ (SPE15) can reach 5.44 × 10^?6 S cm^?1 at 40 °C and 2.35 ×10^?3 S cm^?1 at 140 °C. The SPE15 possesses a wide electrochemical stability window of 0–5 V (vs. Li+/Li) and thermal stability at 140 °C. The excellent properties of this new NWPU‐based SPE are a promising solid electrolyte candidate for all‐solid‐state lithium ion batteries. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45554.     

Influence of LiClO4 on the thermal,mechanical, and morphological properties of P(DMS‐co‐EO)/ P(EPI‐co‐EO) blends

The UV‐vis absorption, thermal analysis, ionic conductivity, mechanical properties, and morphology of a blend of poly(dimethylsiloxane‐co‐ethylene oxide) [P(DMS‐co‐EO)] and poly(epichlorohydrin‐co‐ethylene oxide) [P(EPI‐co‐EO)] (P(DMS‐co‐EO)/P(EPI‐co‐EO) ratio of 15/85 wt %) with different concentrations of LiClO₄ were studied. The maximum ionic conductivity (σ = 1.2 × 10^?4 S cm^?1) for the blend was obtained in the presence of 6% wt LiClO₄. The crystalline phase of the blend disappeared with increasing salt concentration, whereas the glass transition temperature (T_g) progressively increased. UV‐vis absorption spectra for the blends with LiClO₄ showed a transparent polymer electrolyte in the visible region. The addition of lithium salt decreased the tensile strength and elongation at break and increased Young's modulus of the blends. Scanning electron microscopy showed separation of the phases between P(DMS‐co‐EO) and P(EPI‐co‐EO), and the presence of LiClO₄ made the blends more susceptible to cracking. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1230–1235, 2004     

The thermal‐electrical properties of polyvinyl alcohol/AgNO3 films

In this article, one cast technique to fabricate 20–40 wt %AgNO₃‐doped polyvinyl alcohol (PVA) composite films of which electrical resistance sharply dropped (4–5 order) in a certain temperature range was reported. The phase, structure thermal, and electrical resistivity properties of films at different heat treatment temperatures were studied by X‐ray diffraction (XRD), scanning electrical microscopy (SEM) and differential scanning calorimetry (DSC). The results showed that all the AgNO₃ (20–40 wt %) doped PVA films presented an exothermic peak at 182°C. And the temperature of exothermic peak kept constant for various contents of AgNO₃. Meanwhile, the phase composition of the films was greatly affected by the heat treatment temperature. Ag particles were generated during the heat treatment process, and the content of Ag particles increased with increasing the temperature. The resistivity of PVA/AgNO₃ films decreased with increasing the temperature. And a sharp decrease appeared at 155–165°C due to the generation and contact of a mass of Ag particles at this temperature. The thermal‐electrical results suggested the applicability of these materials in temperature sensor, for example, critical temperature resistor thermistor. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Structural,Dielectric Permittivity and Optical Characteristics of Casting Poly Vinyl Alcohol/Calcium Nickel Aluminate Nanocomposite Films

Triplex hybrid nanofiller (CaNiAl₂O₅) have been synthesized by sol-gel method and its nanocomposite (NC) films were incorporated with poly vinyl alcohol (PVA). The scanning electron microscopy (SEM) was used to probe morphological behaviors and dispersion of CaNiAl₂O₅ in PVA matrix. In order to probe the microstructure X-ray diffraction (XRD) and FTIR were performed on PVA/CaNiAl₂O₅ NCs. Based on the results of both XRD and transmission electron microscopy (TEM), the average particle size of the CaNiAl₂O₅ lies in the range 7–15 nm. The current (I) – voltage (V) behaviors were studied using LCR-meter at room temperature. The dc-conductivity increases with increasing in both CaNiAl₂O₅ at different voltages. The dielectric constant exhibits higher values at lower frequency and increases with nanoparticle (NP) loading due to increase in polarization particles in polymer matrix. The ac conductivity tends to increase with increase frequency and NPs content. The cyclic voltammetric data indicate the NC with 8wt% NPs exhibit higher specific capacitance as compared with PVA. The optical constants of the NCs were evaluated from UV-Visible spectra. The band gap energies has a blue shift from 4.4 eV (PVA) to 2.8 eV (PVA/8wt% CaNiAl₂O₅), whereas refractive index (RI) and the optical conductivity of NCs increased with an increasing in NPs content.     

Fabrication of highly monodisperse CeO2@poly(methyl silsesquioxane) microspheres and their application in UV‐shielding films

Highly monodisperse CeO₂@poly(methyl silsesquioxane) (PMSQ) microspheres were successfully prepared by a facile chemical precipitation technique. The structures and properties of CeO₂@PMSQ were analyzed by Fourier transform infrared spectroscopy, X‐ray diffraction, and scanning electron microscopy techniques. We confirmed that the PMSQ microspheres were uniformly coated by CeO₂ nanoparticles, with about an 8 nm crystallite diameter. Then, CeO₂@PMSQ was incorporated into a poly(vinyl alcohol) (PVA) matrix to fabricate PVA/CeO₂@PMSQ composite films by the casting of homogeneous solutions. The thermal and optical properties of the composite films were investigated by thermogravimetric analysis and UV–visible spectroscopy. The results show the high UV‐shielding efficiency of the composites: for a film containing 2.5 wt % CeO₂@PMSQ microspheres, about 80% UV light at wavelengths between 200 and 360 nm was absorbed, whereas the optical transparency in the visible region still remained very high. The addition of CeO2@PMSQ microspheres improved the thermal stability of the PVA films. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45065.