R. F. Bhajantri

Ionic conductivity and dielectric studies of LiClO4 doped poly(vinylalcohol)(PVA)/chitosan(CS) composites

This paper focuses on the dielectric constant (e′), dielectric loss factor (e″) and frequency dependent conductivity (σac) properties of newly prepared poly(vinylalcohol) (PVA) chitosan (CS) composite films incorporated with different concentrations of LiClO4. The composite films were prepared using solution casting technique. The complexation between salt and polymer host is confirmed by FT Raman and UV-Vis studies. The sample containing 20 wt.% LiClO4 exhibits a highest ionic conductivity of 3 × 10-6 S/cm at room temperature. The dielectric properties of the composites follow non-Debye behavior.

Thermal, mechanical and dielectric properties of poly(vinyl alcohol)/graphene oxide composites

In this work the composite films of poly(vinyl alcohol) (PVA) doped with functionalized Graphene Oxide (GO) were prepared by solution casting method. The films were characterized using FT-IR, DSC, XRD, mechanical properties and dielectric studies at room temperature. FTIR spectra shows the formation of hydrogen bonds between hydroxyl groups of PVA and the hydroxy groups of GO. The DSC thermograms shows the addition of GO to PVA greatly improves the thermal stability of the composites. XRD patterns shows that the GO exfoliated and uniformly dispersed in PVA matrix. Mechanical properties are significantly improved in PVA/GO composites. The tensile strength increased from 8.2 to 13.7 MPa and the Young’s modulus increased from 7.5 to 24.8 MPa for 5 wt% GO doped sample. Dielectric spectroscopy showed a highest dielectric constant for the 5 wt% GO doped PVA films. This work provides a potential design strategy on PVA/GO composite, which would lead to higher-performance, flexible dielectric materials, high charg...

High mechanical and pressure sensitive dielectric properties of graphene oxide doped PVA nanocomposites

We report the significant enhancement in mechanical stiffness, Young’s modulus and tensile strength properties of graphene oxide (GO) doped poly(vinyl alcohol) (PVA) nanocomposites. The prepared nanocomposites exhibit a relatively high dielectric constant with a small loss factor and significant response to applied pressure. High mechanical strength is observed for the lower concentration of GO. Recognition to the applied pressure technique has been demonstrated to study the behavior of dielectric and electrical responses. In this study, a unique and sensitive change in dielectric and electrical properties was observed, which can be used to open up new design space for pressure sensing applications.

Thiazole yellow G dyed PVA films for optoelectronics: microstructrural, thermal and photophysical studies

In this paper, we report the microstructural, optical and fluorescence properties of poly(vinyl alcohol) (PVA)/Thiazole Yellow G (TY) dye composite prepared by solvent casting. The formation of change-transfer complex as a result of the interaction between the dye molecules and polymer chain is confirmed in FTIR, FT-Raman, XRD and DSC studies. SEM studies present the morphology of the samples. The UV-visible absorption spectra possess characteristic peaks of the TY dye corresponding to n-π* transition along with a characteristic peak of PVA. The composites exhibit the decreasing energy gap and increasing refractive index with an increase in wt.% of the TY dye. The fluorescence-quenching phenomena are observed in emission wavelength range of 391–406 nm upon excitation in the vicinity of absorption maxima (335 nm) with the quantum yield of 0.72 for lowest concentration of dye. The prepared composites bear high brightness, and improved thermal stability, which make them a promising material for sensors and optoelectronic applications.

Influence of transport parameters on conductivity of lithium perchlorate-doped poly(vinyl alcohol)/chitosan composites

This article focuses on the calculation of transport parameters (number density of ions and time travel of ions between sites, mobility, diffusion coefficient, and number of transitions per unit time) of the lithium perchlorate (LiClO4)-doped poly(vinyl alcohol)/chitosan (PVA/CS) composites using Rice and Roth model. The thermal study reveals a decrease in glass transition temperature for LiClO4-doped PVA/CS composites. The highest ionic conductivity of 3 × 10−6 S cm−1 at room temperature is observed for the 20 wt% LiClO4-containing composite. The temperature-dependent conductivity follows Arrhenius relation and lowest activation energy of 0.153 eV is observed for highest conducting sample. The mechanical properties such as Young’s modulus, stiffness, and tensile strength decreases and its percentage elongation at break increases with increase in LiClO4-doping level in PVA/CS polymer matrix. The scanning electron microscopic images exhibit smooth and homogeneous surface of PVA/CS composite.

Temperature-dependent ionic conductivity and transport properties of LiClO4-doped PVA/modified cellulose composites

This paper presents the investigation on physicochemical properties and ionic conductivity of LiClO4-doped poly(vinyl alcohol) (PVA)/modified cellulose composites. The percolative behaviour of LiClO4 with dc conductivity (σdc) for different LiClO4 weight fractions (p) related to transport dimensionality was also focused. The highest ionic conductivity of 9.79 × 10−6 S cm−1 was observed for 20 wt% LiClO4 doping level at room temperature. The activation energies (Eg) were estimated using temperature-dependent conductivity, which follows the Arrhenius and Vogel–Tammann–Fulcher (VTF) relation. The dynamic fragility (f) and activation energy (Eg) vs. Tg of polymer composites using equivalence of the both Williams–Landel–Ferry (WLF) and VTF equations were also correlated. Transport properties such as travel time of ions between sites ( τo), mobility ( μ), diffusion coefficient (D) and number of transitions per unit time P(E) for normal cationic (Li+) hopping process of LiClO4-doped PVA/mCellulose composites have been investigated using the Rice and Roth model.

Photochromic and microstructural properties of methyl orange doped poly(vinyl alcohol)

The effect of Methyl Orange (MO) dye on microstructural, optical and fluorescence properties of the polymer Poly(vinyl alcohol) (PVA) is studied. The FTIR study shows the appearance of new peaks indicates the interaction of MO with PVA. The UV-Vis study shows three absorption regions with the first two shows red shift and the third one shows blue shift and hence correspondingly three optical energy band gaps. In fluorescence study, it is observed that the intensity increases with increasing wavelength. These results are understood by invoking the hydrogen bonding and hydrophobic interaction between PVA and MO, forms the charge transfer complex (CTC).

Proton conducting diazanium hydrogen phosphate/poly(vinyl alcohol) electrolytes: Transport, electrical, thermal, structural, and optical properties

Proton conducting solid polymer electrolyte films, which are composed of diazanium hydrogen phosphate (DAHP) and poly(vinyl alcohol) (PVA), were prepared by a solution casting method. The prepared films were characterized by ultraviolet-visible, X-ray diffraction, and differential scanning calorimetry. The optical activation energy and band gap increases with increase in DAHP content in PVA. The direct current (DC) and alternating current (AC) conductivity studies have been carried out using an impedance analyzer. The sample containing 15 wt% DAHP shows highest AC conductivity of the order of 10−4 S cm−1 and DC conductivity about 4.27 × 10−7 S cm−1 at ambient conditions. The crystallinity has decreased and glass transition temperature (T g) has increased with increase in DAHP content. The Williams–Landel–Ferry and Vogel–Fulcher–Tamman equations were used to calculate dynamic fragility (m) and apparent activation energy (E g) from T g values. The Rice and Roth model was successfully applied to determine the transport parameters for DAHP/PVA electrolytes. This article mainly focused on understanding the contribution of different parameters to conductivity phenomenon in solid polymer electrolytes.

Influence of ZrO 2 filler on physico-chemical properties of PVA/NaClO 4 polymer composite electrolytes

AbstractThe ZrO2-filled PVA/NaClO4 polymer nanocomposite is a freestanding electrolyte film and is prepared using the solution casting method in an aqueous medium. These prepared samples were characterized for structural, morphological, optical, thermal, and electrical properties. FT Raman studies confirmed the interaction between PVA and NaClO4, and dispersion of ZrO2 fillers in the PVA/NaClO4 polymer electrolyte. The surface roughness was observed from AFM images. Fitting the values of UV absorption to Tauc’s equation, the optical energy band gaps have been evaluated and correlated to the electrical conductivity. The maximum electrical conductivity of 4.3 × 10−3 (± 0.0002) S/cm was obtained for 3 wt% ZrO2-filled PVA/NaClO4 polymer nanocomposite. The thermal degradation kinetic parameter was calculated by fitting thermo gravimetric analysis values in Broid’s model. Graphical abstractPossible interaction of ZrO2 filled PVA/NaClO4 reflected in Raman peaks in FT-Raman spectra

Effect of Al2O3 on dielectric behavior of LiClO4/PVA polymer electrolytes

The dielectric properties of lithium per chlorate (LiClO4)/polyvinylalcohol (PVA) solid polymer electrolyte dispersed with alumina (Al2O3) nanoparticles have been investigated in this work. Free standing films of Al2O3/LiClO4/PVA were prepared using solution casting method. FTIR results confirm the successful dispersion of Al2O3 in LiClO4/PVA polymer matrix. The variation in dielectric constant follows Non-Debye type behavior. The interfacial polarization phenomenon is the main reason for lower frequency regime variation in dielectric properties. The inertial properties of the dipoles play vital role in higher frequency regime. The composites with 5wt% Al2O3doped LiClO4/PVA show highest conductivity, can be used as an electrolyte with certain attainable modifications.