Role of CoBr2 on the structural,optical and magnetic properties of polyvinyl alcohol films

Polyvinyl alcohol (PVA) films filled with different concentrations of CoBr₂ were prepared using the casting method. These films were characterized by FTIR, UV–visible, XRD, and ESR techniques. FTIR spectra were used to clarify the structural variations due to the filling level from CoBr₂. The observed bands at 3484, 1733, and 1640 cm^?1 were assigned to O? H, C?O, and C?C stretching vibrations, respectively. UV–visible spectra shows the absorption band at 280 nm which is assigned to π → π* transition. This indicates the presence of unsaturated bonds in tail to head of PVA. Optical energy gap decreased with increasing the concentration of CoBr₂. X‐ray diffraction scans show some decrease in the degree of crystallinity in the filled films which reveals an increase in amorphous phase of PVA due to the interaction between Co⁺² and polymeric matrix causing a molecular rearrangement within the amorphous phase of PVA. The observed complex ESR spectrum due to hyperfine interactions confirms the role of free radicals. Spectroscopic and magnetic properties of PVA/CoBr₂ composite films were investigated and compared with those of PVA alone. The results show that the change of the structure due to the interaction of filler with the polymer. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Enhancement of thermal stability associated with the chemical treatment of bacterial (Gluconacetobacter xylinus) cellulose

Bacterial cellulose produced by Gluconacetobacter xylinus was treated with sodium carbonate (Na₂CO₃) and sodium hydroxide (NaOH) to remove entrapped noncellulosic materials. Fourier transform infrared (FTIR) spectroscopy has been used to investigate the effect of alkali on the chemical structure of bacterial cellulose. The changes in the crystalline nature of these membranes were analyzed using X‐ray diffraction (XRD) technique. The morphology and the removal of noncellulosic impurities followed by alkali treatment were studied using scanning electron microscopy (SEM) and energy dispersive X‐ray spectrometry (EDS). The enhanced thermal stability of bacterial cellulose was evident from thermogravimetric analysis (TGA). Further, the alkali treatments resulted in relatively pure form of cellulose, which finds application in various spheres. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Investigation of optical and thermally stimulated properties of SiO2 nanoparticles‐filled polycarbonate

Polycarbonate nanocomposite containing silicon oxide nanoparticles average size of 5 nm at different weight ratio has been prepared by solution mixing method. The dispersion of nanoparticles in polymer matrix was studied by transmission electron microscopy (TEM). The optical and thermally stimulated behavior of nanocomposites were analyzed by energy dispersive X‐ray spectra (EDX), X‐ray diffraction pattern (XRD), UV–vis spectroscopy, differential scanning calorimetry (DSC), and thermally stimulated discharge current (TSDC). TEM images show the dispersion and size of the nanoparticles, however, EDX indicate the presence of SiO₂ on the surface of the nanocomposite film. An XRD result reveals that the crystallinity increases with increase in concentration of SiO₂ nanoparticles in polymer matrix. The direct and indirect optical energy band gaps decreased and number of carbon atom increased with concentration of SiO₂ nanoparticles. We have observed that the increase of SiO₂ nanoparticles in PC significantly reduces the refractive index. DSC and TSDC show that glass transition temperature increases according to SiO₂ weight ratio. The TSDC of nanocomposites samples could be understand in terms of non‐Debye theory of charge relaxation and co‐tunneling mechanism of charge transport. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Nanofiber organic semiconductors: The effects of nanosize on the electrical charge transport and optical properties of bulk polyanilines

The electrical transport, optical, and microstructural properties of bulk polyaniline (PANI) and nano‐PANIs were investigated. A field emission scanning electron microscopy (SEM) image of bulk PANI showed macroscopic and aggregated granular particles. A SEM image of the nanostructured PANI showed the formation of one‐dimensional nano/microstructures. The formation of nanofibers was observed from the transmission electron microscopy image. The electrical conductivities of the bulk and nanostructured PANIs increased with increasing temperature, which indicated semiconductor behavior. The electrical conductivities of the bulk and nanostructured PANIs at room temperature were found to be 2.12 × 10^?5 and 1.80 × 10^?2 S/cm, respectively. The electrical conductivity of the nanostructured PANI was about 850 times higher than that of the bulk PANI. The obtained band gaps of the bulk and nanostructured PANIs were determined from diffuse reflectance measurements and were found to be 3.27 and 2.41 eV, respectively. The refractive index of the PANI samples changed from 1.3 to 1.61. The obtained results indicate that the electrical and optical properties of the PANI were inherently dependent on the nanostructure. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Optical anisotropy and non-linear optical properties of azobenzene methacrylic polymers

Photoinduced optical anisotropy has been studied in several methacrylic copolymers, either amorphous or liquid crystalline, with cyano azobenzene chromophores in the side chain. Illumination with linearly polarised 488 nm light gives rise to high and stable values of birefringence and dichroism, mainly in liquid crystalline films. Both dichroism and birefringence decrease with the azo content in the copolymer series while some increase can be achieved by the incorporation of biphenyl molecules to the copolymers. Photoinduced anisotropy disappears above the glass transition temperature in amorphous polymers, whereas it increases in liquid crystalline polymers (LCP) due to a thermotropic self-organisation.The non-linear optical (NLO) properties of the films have been studied by second harmonic generation (SHG) measurements. The intensity of the harmonic signal from in situ corona poled polymeric films has been measured. The effect of 488 nm light irradiation on the azo chromophores orientation and consequently on the NLO response of the films was investigated at different temperatures. The intensity and thermal stability of the second harmonic signals obtained after the two different (thermal and photoassisted) corona poling processes have been compared.     

X‐ray photoelectron spectroscopy and electrical conductivity of polyaniline doped with dodecylbenzenesulfonic acid as a function of the synthetic method

X‐ray photoelectron spectroscopy (XPS) has been employed to investigate the protonation degree of polyaniline doped with dodecylbenzenesulfonic acid (Pani. DBSA) obtained by different synthetic methods. The protonation degree has been compared to electrical conductivity. Pani.DBSA prepared through the redoping process in an agate mortar displays conductivity values within the range of 1 S/cm. A protonation level of 48% with almost all imine groups being protonated. Pani.DBSA was also synthesized by oxidative polymerization of aniline in the presence of DBSA, which acts simultaneously as a surfactant and as protonating agent. This in situ doping polymerization was carried out in aqueous or toluene media. In both cases, protonation degrees higher than 50% have been achieved, indicating that a substantial portion of amine units have also been protonated. Higher doping degree has been achieved by aqueous dispersion polymerization of aniline. The C/N and S/N molar ratios obtained by XPS analysis indicate that the polyaniline chains obtained by in situ polymerization are protonated by both sulfonate and hydrogen sulfate anions. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 556–565, 2001     

Thermal and structural properties of poly(vinyl alcohol) doped with hydroxypropyl cellulose

The growth and importance of medical and related health care and hygiene textile sectors are attributed to the improvement and innovations in both textile technology and medical procedures. The aim of this study was to examine some of the structural properties of pure poly(vinyl alcohol) (PVA) and hydroxypropyl cellulose (HPC) doped PVA of different weight percentages. This will lead to the choice of the optimum conditions suited for specific medical and surgical applications for which textile materials are currently used. Thermogravimetry was used to develop an instrumental system for the study of thermal stability and for identification of the individual components of several polymer blends. Derivative thermogravimetry provided clear information and distinguished between different generic types. Also, differential scanning calorimetry and its derivatives gave accurate values of glass‐transition temperature and melting temperature and gave detailed features of the steps of weight loss and changes in the heat of fusion. The X‐ray diffraction technique was used to determine the crystallinity/amorphosity ratio and the change in crystallite size at different dopant concentrations. The effect of doping with HPC on PVA structure was studied with spectrophotometric analyses. Variations in the group coordination in the IR region were followed. The data obtained indicated that measurable and remarkable changes in the thermal stability of PVA occurred at different doping concentrations. This may have been because the diffusion of dopant caused structural changes in the polymer matrix. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1914–1923, 2005     

Preparation and optical properties of transparent epoxy composites containing ZnO nanoparticles

Polymer nanocomposites are usually made by incorporating dried nanoparticles into polymer matrices. This way not only leads to easy aggregation of nanoparticles but also readily brings about opaqueness for nanocomposites based on functionally transparent polymers. In this letter, transparent ZnO/epoxy nanocomposites with high‐UV shielding efficiency were prepared via two simple steps: first, in situ preparation of zinc hydroxide (Zn(OH)₂)/epoxy from the reaction of aqueous zinc acetate (Zn(Ac)₂·2H₂O) and sodium hydroxide (NaOH) at 30°C in the presence of high‐viscosity epoxy resin; second, thermal treatment of the as‐prepared Zn(OH)₂/epoxy hybrid into ZnO/epoxy composites. Optical properties of the resultant ZnO/epoxy nanocomposites were studied using an ultraviolet–visible (UV–vis) spectrophotometer. The nanocomposites containing a very low content of ZnO nanoparticles (0.06 wt %) possessed the optimal optical properties, namely high‐visible light transparency and high‐UV light shielding efficiency. Consequently, the as‐prepared ZnO/epoxy nanocomposites are promising for use as novel packaging materials in lighting emitting diodes technology. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Investigation of third‐order nonlinear optical properties of pyrazoline‐doped polyvinyl alcohol films

A 2‐pyrazoline,3‐(phenyl)‐5‐(4‐N,N‐dimethylaminophe nyl)‐1H‐2‐pyrazoline (PDAP) was synthesized and characterized by Fourier transform infrared, nuclear magnetic resonance, ultraviolet (UV)–visible, and Z‐scan techniques. The PDAP‐doped polyvinyl alcohol composite films were prepared by solvent casting method using dimethylformamide as solvent. The optical properties of the composites were studied using UV–visible, steady state fluorescence, single beam Z‐scan technique and degenerate four wave mixing (DFWM) technique. The optical constants such as band gap and optical activation energy were evaluated. The steady state fluorescence data showed both emission peak wavelengths and intensity change with PDAP‐doping level in the composites. The open aperture Z‐scan of the composite films displayed reverse saturable absorption. A self‐focusing effect was observed under closed aperture configuration and the nonlinear refractive index of the film was observed increasing with the increase of doping. The third‐order nonlinear susceptibility was compared with that obtained with picoseconds pulses through DFWM technique. The thermogravimetry analysis shows that the composites are thermally stable up to 260°C. POLYM. ENG. SCI., 2013. © 2013 Society of Plastics Engineers     

Mechanical,electrical, and dielectric properties of polyvinylidene fluoride/short carbon fiber composites with low‐electrical percolation threshold

In this investigation, polyvinylidene fluoride (PVDF)/short carbon fiber (SCF) composites have been prepared by solution casting technique to enhance electrical and dielectric properties with very low‐electrical percolation threshold (0.5 phr SCF). The effect of SCF content on mechanical, thermal and morphological properties of the composites have also been investigated. The mechanical properties of the composites are found to reduce compared to neat PVDF due to poor polymer–filler interaction which can be concluded from FESEM micrographs showing poor bonding between PVDF and SCF. The PVDF/SCF composites exhibit either positive temperature coefficient effect of resistivity or negative temperature coefficient effect of resistivity depending on the loading of SCF in the polymer matrix. The change in conductivity during heating–cooling cycle for these composites shows electrical hysteresis along with electrical set. The melting point of the composites marginally increases with the increase in fiber loading in PVDF matrix as evidenced from DSC thermograms. X‐ray diffraction analysis reveals the crystallinity of PVDF decreases with the increase in SCF loading in matrix polymer. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39866.     

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.     

Third-order nonlinear optical properties and two-photon absorption in polymers doped with p-phenyl sydnone

We report the measurements of the third-order susceptibilities and two-photon absorption in three different polymers doped with p-phenyl sydnone moiety viz., 2-benzylhydrazono-5-(3-p-tolylsydnone-4-yl)1,3,4,-thiadiazine, which is recently synthesized and characterized, with the prospective of reaching a good compromise between processability and high nonlinear optical properties. The measurements were done using nano second Z-scan at 532nm. The Z-scan spectra reveal a large negative nonlinear refraction coefficient n₂ of the order 10⁻¹⁴ cm²/W and a two-photon absorption β, which is determined to be the order of cm/GW. The absorption cross section is 10⁻⁴⁶ cm⁴ s/photon. The molecular second-order hyperpolarizability in PMMA matrix was calculated to be 1.47 × 10⁻³¹ esu, comparable with stilbazolieum derivatives, a well-known class of optical materials for photonics and biophotonics applications. The chromophore shows its optical power limiting behavior in all the three polymer matrices. All these results suggest that this moiety has potential for the application of all-optical limiting and switching devices. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Thermal and optical properties of gelatin/poly(vinyl alcohol) blends

Differential scanning calorimetry, thermogravimetric analysis, X‐ray diffraction, and ultraviolet–visible spectroscopy of gelatin and poly(vinyl alcohol) (PVA) homopolymers and their blended samples were studied. The data revealed that the gelatin and PVA polymers were compatible over the investigated range of compositions; this contributed to the formation of hydrogen‐bonding interaction between their polar groups. The associated enthalpy‐of‐melting transition and thermal stability of the blended samples increased with increasing PVA content. This indicated that the crystalline structure of PVA was not destroyed completely in the blends, which was consistent with the X‐ray diffraction pattern of the 50/50 (wt %/wt %) blended gelatin/PVA sample. The absorption edge and optical band gap for allowed direct transition were determined from ultraviolet–visible spectra. The induced changes in the band structure are elucidated. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Structural,mechanical, and electrical properties of electropolymerized polypyrrole composite films

Electrochemical polymerization of pyrrole in a solution containing dissolved poly(vinyl alcohol) (PVA) produces a homogeneous, free‐standing, flexible, and conductive polymer film. The films were characterized using infrared spectroscopy, wide‐angle X‐ray diffraction analysis, and scanning electron microscopy. The appearance of standard and some new absorption bands for polypyrrole (PPy) and PVA confirms the composite formation. The mechanical properties of conducting PVA + PPy films were studied and found to be improved with respect to the control PPy films. The electrical conductivity of the PVA + PPy films was measured by using standard four‐ and two‐probe methods. The conductivity of the films was found to depend on the pyrrole content. These conducting composites were further used as gas sensors by observing the change in current with respect to ammonia gas. It was observed that the current decreases when these composites were exposed to ammonia gas. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2511–2517, 2001     

The stability of gahnite doped with chromium pigments in glazes from the French manufacture of Sèvres

The French manufacture of Sèvres, famous for its production of fine porcelain artifacts, has been synthesizing pink pigments mainly composed of the spinel phase ZnAl_2?xCr_xO₄ with x varying from 0.25 to 0.41 since the middle of the 19th century. This kind of pigment is mixed with an uncolored frit to obtain decorations for porcelain artifacts. However, the pink color of the pigment is altered in a particular uncolored frit and a brownish color appears. The mechanism of this color change was investigated. Observations under a scanning electron microscope revealed the formation of a phase rich in Cr resulting from reactions between the uncolored frit and the pigment during firing. X‐ray diffraction combined with Rietveld refinements and X‐ray absorption near edge structure measurements at the Cr K‐edge showed that the new formed phase belongs to the same spinel phase ZnAl_2?xCr_xO₄ than the pigment, but with a higher Cr content x. We showed that its formation and thus the stability of the pigment is driven by the Al content in the uncolored frit.     

Solid terpolymer electrolyte based on poly(vinyl butyral‐co‐vinyl alcohol‐co‐vinyl acetate) incorporated with lithium salt and tetraglyme for EDLCs

Solid terpolymer electrolytes (STEs) consist of different ratios of poly(vinyl butyral-co-vinyl alcohol-co-vinyl acetate) (PVBVA) and bis(trifluoromethane) sulfonamide lithium salt (LiTFSi) were prepared and the ionic conductivity of the prepared STEs was evaluated. The optimized STE (denoted as STE 20) was further doped with various amount of tetraglyme (10, 20, and 30 wt % and denoted as G10, G20, and G30, respectively). G20 enhanced the ionic conductivity from 6.22 (for STE 20) to 21.9 µS cm⁻¹. This enhancement is due to the presence of abundant oxygen-containing functional group in tetraglyme that provides more charge carrier mobility in the polymer matrix. The structure and complexation of the materials are authenticated via X-ray diffraction and Fourier transform infrared spectroscopy analysis. The performance of electric double layer capacitors based on activated carbon (AC) fabricated with STE 20 (AC/STE 20/AC) and G20 (AC/G 20/AC) were studied via cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy. AC/G 20/AC achieved the maximum specific capacitance of 10.20 F/g [which is higher than AC/STE 20/AC (9.30 F/g)] with 75% of specific capacitance retention after 1500 cycles. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45902.     

Influence of grafting on structural and optical properties of nylon‐6 fibers

This study throws light on the change of the optical properties and some structural properties due to graft copolymerization of polydiallyldimethyl ammonium chloride (PDADMAC) and polyacrylamide (PAA) of nylon‐6 fibers. Multiple‐beam interferometric technique in transmission was used to study the change of the diameter, refractive indices, and birefringence of nylon‐6 fibers at different graft yields. The results were utilized to investigate the isotropic refractive index, the mean polarizabilities per unit volume, dielectric constant, dielectric susceptibility, and surface reflectivity for nylon‐6 and grafted nylon‐6 fiber. The effect of grafted PAA onto modified nylon‐6 fibers containing PDADMAC on the crystallinity was studied by X‐ray diffraction. These results reflect good effect of grafting on the optical and structural properties of nylon‐6 fibers. The opto‐thermal properties of grafted PAA with different graft yields have been studied. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

New second-order nonlinear optical polymers containing the same isolation groups: Optimized syntheses and nonlinear optical properties

Based on control experiments, a new series of second-order nonlinear optical polymers with fluorene moieties as isolation spacers were successfully prepared. In the polymers, the chromophore moieties were embedded into the polymer backbone with one position at the donor side, and another point in the π bridge. Different acceptors were used to construct the push-pull structure of chromophore moieties, including nitro groups, sulfonyl groups, 3-phenyl-5-isoxazolone, 1,3-diethylthiobarbituric acid and TCF groups. The tested NLO properties of the polymers demonstrated that the isolation groups with big size do not always benefit the resultant NLO effect. Also, for different acceptors, there should be different suitable isolation groups to balance the good and bad effects caused by the introduced isolation spacers.     

Investigation of electrical conduction mechanism in double‐layered polymeric system

The electrical conduction in solution‐grown polymethylmethacrylate (PMMA), polyvinylidenefluoride (PVDF) and PMMA‐PVDF double‐layered samples in the sandwich configuration (metal‐polymer‐metal) was investigated at different fields in the range 100–120 kV/cm as a function of temperature in the range 293–423 K for samples of constant thickness of about 50 μm. Certain effects which lead to a large burst of current immediately after the application of field were observed in double‐layered samples. An attempt was made to identify the nature of the current by comparing the observed dependence on electric field, electrode material and temperature with the respective characteristic features of the existing theories on electrical conduction. The observed linear I‐V characteristics show that the electrical conduction follows Pool‐Frenkel mechanism in PMMA and PVDF samples. Whereas, the non‐linear behavior of current‐voltage measurements in PMMA‐PVDF double‐layered samples have been interpreted on the basis of space charge limited conduction (SCLC) mechanism. The conductivity of the polymer films increased on formation of their double‐layer laminates. The polymer‐polymer interface act as charge carrier trapping centres and provides links between the polymer molecules in the amorphous region. The interfacial phenomenon in polymer‐polymer heterogeneous system has been interpreted in terms of Maxwell‐Wagner model. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Structural,electrical, and optical studies of plasma‐polymerized and iodine‐doped poly pyrrole

An attempt was made to study the structural, electrical, and optical properties of plasma‐polymerized pyrrole and iodine‐doped pyrrole. A comparative study of the IR spectra of the monomer and polymer pyrrole gives information that the ring structure is retained during plasma polymerization. Iodine doping considerably increases the conductivity of the polymer film and decreases the optical band‐gap energy. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1856–1859, 2002