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 Table of Contents  
ORIGINAL ARTICLE
Year : 2016  |  Volume : 10  |  Issue : 1  |  Page : 52-58

Significant enhancement of dielectric and conducting properties of electroactive polymer polyvinylidene fluoride films: An innovative use of Ferrum metallicum at different concentrations


1 Centre for Interdisciplinary Research and Education, 404 B, Jodhpur Park, Kolkata; Department of Physics, Jadavpur University, West Bengal, India
2 Centre for Interdisciplinary Research and Education, 404 B, Jodhpur Park, Kolkata; Department of Physics, Jogamaya Devi College, Kolkata, West Bengal, India
3 Centre for Interdisciplinary Research and Education, 404 B, Jodhpur Park, Kolkata; Department of Physics, Jadavpur University; Department of Physics, n Institute of Engineering Science and Technology, Shibpur, Howrah, West Bengal, India
4 Centre for Interdisciplinary Research and Education, 404 B, Jodhpur Park, Kolkata, West Bengal, India
5 Central Council for Research in Homoeopathy, New Delhi, India

Date of Submission17-Dec-2015
Date of Acceptance03-Mar-2015
Date of Web Publication21-Mar-2016

Correspondence Address:
Papiya Nandy
Centre for Interdisciplinary Research and Education, Kolkata - 700 068, West Bengal
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0974-7168.179154

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  Abstract 

Background: There are experimental evidences of nanoparticle aspect of homoeopathic medicine. It has also been established that the size of these nanoparticles (NPs) decrease with increase in potency.
Aim: We have used this aspect of homoeopathic medicines in some technical applications. Here, to improve the electrical properties of an electroactive polymer, poly (vinylidene fluoride-hexa-fluoropropylene) (PVDF-HFP), we have incorporated in the polymer film, a very novel and unique probe Ferrum metallicum (FeM), a homoeopathic medicine, the size of which can be changed by dilution, followed by controlled agitation.
Settings and Design: The composite film was synthesized by solution-casting technique. Using standard procedures, the characterization studies by X-ray diffraction, field-emission scanning electron microscope, and Fourier transform infrared spectroscopy were performed to check the incorporation of the NPs in the film.
Material and Method: Each sample was freshly prepared 2 times by doping FeM in PVDF-HFP matrix using solution-casting technique, and the experiment was repeated with each sample for 5 times.
Statistical Analysis: This being a continuous data recording, error bars cannot be shown. We have presented the graphs which have been repeated maximum number of times.
Result and Conclusion: Our result shows that the electrical properties such as dielectric constant, tangent loss, and electrical conductivity of these polymer films get significantly modified due to incorporation of this homoeopathic nanomedicine and the effect increases with the increase in concentration of the probe up to a critical value. These FeM-incorporated PVDF-HFP films will have potential applications as high-energy storage devices such as multilayered high-charge storage device.

Keywords: A.C. conductivity, Dielectric constant, Nanoparticles, Polymer film, Tangent loss


How to cite this article:
Paul B K, Kar S, Bandyopadhyay P, Basu R, Das S, Bhar D S, Manchanda RK, Khurana A, Nayak D, Nandy P. Significant enhancement of dielectric and conducting properties of electroactive polymer polyvinylidene fluoride films: An innovative use of Ferrum metallicum at different concentrations. Indian J Res Homoeopathy 2016;10:52-8

How to cite this URL:
Paul B K, Kar S, Bandyopadhyay P, Basu R, Das S, Bhar D S, Manchanda RK, Khurana A, Nayak D, Nandy P. Significant enhancement of dielectric and conducting properties of electroactive polymer polyvinylidene fluoride films: An innovative use of Ferrum metallicum at different concentrations. Indian J Res Homoeopathy [serial online] 2016 [cited 2019 Jul 20];10:52-8. Available from: http://www.ijrh.org/text.asp?2016/10/1/52/179154


  Introduction Top


In recent times, electroactive polymer films have become the subject of intense research interest due to their good electrical and other properties. Polyvinylidene fluoride (PVDF) and its polymers are selected from the whole range of these polymers for their versatile applications.[1],[2],[3],[4],[5] The electrical properties of these polymers can be greatly enhanced by using suitable fillers.[4],[5],[6],[7],[8],[9],[10],[11],[12],[13],[14],[15] In our endeavor in the search for a suitable nontoxic, easily available and low-cost filler, we have thought of a very novel and unique idea of using triturated iron particles, a commonly used homoeopathic nanomedicine Ferrum metallicum (FeM).

That the homoeopathic medicines are active even at a very low dilution has been challenging for the scientists and many different hypotheses had been proposed. Out of all these, the proposal of formation of nanoparticles (NPs) at high potency (the process of potentization is dilution, followed by succussion) of these medicines had been experimentally proved.[16],[17],[18],[19]

We have utilized this property of nanoparticle formation of homoeopathic medicine for the first time in technological applications and reported here the enhancement of electrical properties of (PVDF-hexa-fluoropropylene) (PVDF-HFP) by incorporating triturated iron NPs FeM in the polymer matrix. We have been able to improve the electrical properties, namely dielectric constant, conductivity, and tangent loss of the film by changing the concentration of FeM up to a certain critical concentration.

At a time when electroactive polymer films are gaining worldwide attention due to their suitable electrical properties,[4], 6, [12],[13],[14],[15] this simple fabrication and nontoxic method will make these FeM-incorporated polymer film an alternative for traditional electroactive ceramics [5],[8],[9],[10] and hence the outcome of this experiment is of great significance.


  Materials and Methods Top


The materials used in the synthesis of FeM-doped polymer (FeMP) are PVDF-HFP (Sigma Aldrich, USA.) and dimethyl sulfoxide (DMSO) (Merck, India). Freshly prepared FeM at potency 200C was obtained from Hahnemann Publishing Company, India.

The FeMP was synthesized by solution-casting method. In a typical synthesis, 100 mg of PVDF-HFP was added in 2 ml DMSO and mixed together under vigorous stirring at 60°C for 3 h. Measured amounts of the FeM at 200C potency were added to the solution. FeMP was obtained by casting the whole mixture in clean dry Petri dishes and evaporating the solvent in an incubated oven at 60°C for 12 h. As we know DMSO cannot be totally removed, we did all our measurements with the residual DMSO. The films were then coated by silver paste on both sides for electrical measurements. The synthesized films had the thickness in the range of 40–60 μm as measured by using a digital screw gauge.[11],[15],[20]

Sample Details

  • 100 mg PVDF-HFP + 2 ml DMSO + No FeM (0 FeMP)
  • 100 mg PVDF-HFP + 2 ml DMSO + 0.l ml FeM at 200C (0.1 FeMP)
  • 100 mg PVDF-HFP + 2 ml DMSO + 0.2 ml FeM at 200C (0.2 FeMP)
  • 100 mg PVDF-HFP + 2 ml DMSO + 0.5 ml FeM at 200C (0.5 FeMP)
  • 100 mg PVDF-HFP + 2 ml DMSO + 1.0 ml FeM at 200C (1.0 FeMP)
  • 100 mg PVDF-HFP + 2 ml DMSO + 2.0 ml FeM at 200C (2.0 FeMP).


Instrumentation

The characteristic stretching and bending modes of vibration of chemical bonds of these samples were effectively evaluated by Fourier transform infrared spectroscopy ([FTIR]-8400S, Shimadzu). Dielectric measurements of these films were carried out by an electrometer (HP Model 4274 A, Hewlett-Packard, USA). Electrical properties such as dielectric permittivity (εr), dissipation factor (tan δ), and A.C. conductivity (σA.C) of all FeMP samples were measured in the frequency range of 20 Hz to 2.0 MHz using LCR meter (HP Model 4274 A, Hewlett-Packard, USA). Field-emission scanning electron microscopy (FESEM) was done by using INSPECT F50 SEM, FEI Europe BV. The operating conditions are mentioned in the FESEM images as follows: HV 20.00 kV, mag 5000x, WD 10.9 mm, and HFW 59.7 μm. Sample preparation was done by using Turbo-Pumped Sputter Coater EMS 150TS and was used for gold coating.


  Results and Discussion Top


Fourier Transform Infrared Spectroscopy Analysis

The FTIR spectra of all FeMPs that show characteristic absorbance bands at 488, 532, 613, 763, 796, and 975 cm −1 corresponding to the α-phase and at 481, 511, 600, 839, and 1070 cm −1 corresponding to the β-phase have been observed.[11],[15],[20] The spectra indicate that there is no phase shift or chemical interaction between the nanomedicine and the polymer film, but the intensity of α- and β-phases change with the concentration of FeM [Figure 1].
Figure 1: Fourier transform infrared spectra of FeM-doped polymer films for all concentrations of FeM at 200C potency

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Field-emission Scanning Electron Microscope Analysis

[Figure 2] shows the morphology and microstructures of FeMP samples loaded with nano medicine FeM at 200C potency and of different concentrations. In [Figure 2]a and [Figure 2]b, the particles are more scattered, whereas [Figure 2]c shows the evidence of large number of agglomerated particles embedded in polymer matrix. Evidence for the inclusion of Fe in the polymer was not very conclusive as the sample was of extreme dilution and was difficult to detect the presence of particle. However, we realized that the particles seen in the FESEM are Fe particles as their number density changed with higher concentration of added Fe.
Figure 2: Field-emission scanning electron micrograph of FeM-doped polymer films for different concentrations of FeM at 200C potency. (a) 0.2 ml of FeM, (b) 0.5 ml of FeM, and (c) 2 ml of FeM

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Dielectric Constant Measurements

The dielectric constant (εr) of each sample was calculated using the formula,

εr= (Cp* d)/Aε0,

where εr, Cp, d, A, and ε0 are the dielectric constant of the material, capacitance, thickness of the film, area of cross-section, and permittivity of free space, respectively.

The variations of dielectric constant with frequency of all FeMP films are shown in [Figure 3]. From the figure, it is clearly seen that throughout the whole frequency range, dielectric constant has substantially higher values in case of all FeMP films compared to the pure polymer film. The value increases with the concentration of FeM up to a critical value of 0.5 ml of FeM added in the polymer film, after which the value decreases. It is also seen that within the frequency range 20 Hz to 2 MHz, dielectric constant of FeMP films decreases continuously with increasing frequency for all concentrations of FeM up to 200 Hz and after that the rate of decrease slows down.
Figure 3: Variation of dielectric constant with frequency for FeM-doped polymer for all concentrations of FeM at 200C potency

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Enhancement of dielectric constant at lower frequency may be explained from interfacial polarization occurred in the interfaces between insulators (e.g., PVDF-HFP) and conducting materials (e.g., FeM). This effect overrules the effect of orientation of dipoles at lower frequency. As the frequency is increased further, dipole response is restricted and the dielectric constant has a saturation tendency. In this case, the internal individual dipoles contribute to the dielectric constant which is nothing but the electronic polarization effect.[11],[15],[20]

At a higher doping concentration, dielectric constant decreases due to the presence of more agglomerated particles present in the composite system thereby reducing the interfacial area. This phenomenon can be also explained by FESEM micrograph [Figure 3].

Tangent Loss Measurement

The tangent loss, tan δ, of a medium includes dielectric damping loss and conductivity loss of the material and is the ratio of conduction current and displacement current.

tan δ = σa.c./(2 π f ЄrЄo).

From [Figure 4], it is clearly seen that throughout the frequency range, tangent loss continuously decreases exponentially with increasing frequency for all FeMP films up to 10 KHz. At comparatively lower frequency range, the dipoles can orient easily with external electric field. This phenomenon is mainly responsible for intermolecular friction or vibration, which contributes to the exponential decrease of tangent loss.
Figure 4: Variation of tangent loss with frequency for all FeM-doped polymer films at 200C potency

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As the frequency increases further, polarization effect is less as the dipoles cannot follow the rapidly changing applied electric field and there is no further tangent loss.

The increase in tangent loss above 100 KHz frequency arises due to the contribution from the conduction of metal NPs through the polymer.[11],[15],[20]

[Figure 4] shows that the sample 0.2 FeMP has the maximum tangent loss perhaps due to the formation of more conducting pathway, i.e., leakage current. Further increase of doping element may inhibit the conducting pathways resulting in low tangent loss.

A.C. Conductivity Measurement

A.C. conductivity (σa.c.) is given by,

σa.c.=2 π f tan δ ЄrЄo

where f, tan δ, Єr, and Єo are the frequency in Hz, tangent loss factor, dielectric constant of the material, and vacuum permittivity, respectively.

The A.C. conductivity increases with all frequencies as shown in [Figure 5]. The conductivity is maximum for 0.2 FeMP due to the formation of more conducting pathway, i.e., leakage current. Further increase of doping element may inhibit the conducting pathways resulting in low conductivity. The exponential increase in conductivity with frequency arises due to the increase in mobility of iron particles present in the polymer matrix.[11],[15],[20]
Figure 5: Variation of A.C. conductivity with frequency of FeM-doped polymer films of all concentrations at 200C potency

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  Conclusions Top


FeMPs with different concentrations of FeM have been synthesized by solution-casting technique and their phase evolution, dielectric properties, and A.C. conductivity have been investigated.

Gradual addition of FeM in PVDF-HFP leads to gradual increase in α-phase at the cost of electroactive β-phase as observed from the FTIR spectra. The dielectric constant of FeMPs at all concentrations of FeM is higher than the pure polymer throughout the frequency range of 20 Hz to 2 MHz [Figure 3]. The tangent loss of this film is also considerable in that frequency range [Figure 4].

The dielectric constant is highest for 0.5 FeMP. Perhaps, the composite reaches the optimum conformation of α- and β-phases at this concentration of FeM to exhibit the maximum dielectric constant [Figure 3], which in turn is responsible for the low tangent loss as shown in [Figure 4]. However, A.C. conductivity is high for 0.2 FeMP [Figure 5], giving rise to high tangent loss [Figure 4].

The electrical conductivity increases with frequency for all FeMP films [Figure 5] due to the presence of mobile metal ions in the polymer composites. As tan δ is a measure of the ratio of conduction current and displacement current, its value also increases with increase in conductivity [Figure 4].

We can compare this result using homoeopathic source of Fe nanoparticle with our earlier study of homogenous dispersion of Fe2O3 NPs, as obtained from chemical (nonhomoeopathic) sources, in the polymer matrix.[11] We have shown that the incorporation leads to strong interfacial interaction between the NPs and the polymer resulting in enhanced dielectric constant of the thin films. The observed variation of the dielectric properties of the thin films has been explained on the basis of surface charge, size, geometrical shape, and extent of agglomeration of the NPs in the polymer matrix. Similarly, dielectric constant, tangent loss, A.C. conductivity, and resistivity of composites with increasing concentration of Fe metal ion at different temperatures have been studied by us.[21] The results showed that dielectric constant decreased with frequency for all the samples attaining constancy at higher frequency, followed by electronic polarization. A.C. conductivity increased with frequency, and was found to depend on the concentration of mobile ions present in the composites.

Thus, pure polymer film which has comparatively low dielectric constant can be modified into materials with enhanced dielectric constant and comparatively low tangent loss by making a composite with homoeopathic nanomedicine FeM, which are nontoxic, eco-friendly, and easily available in the nano form. Our similar work using other metal NPs also gives promising result and compares well with this result.[11],[21],[22],[23]

As a dielectric material, these FeMP films can then be a promising candidate for the fabrication of high-charge storing multilayer capacitors and can be used for electronic industries.

Acknowledgement

The authors are thankful to the Central Council for Research in Homoeopathy (CCRH), Ministry of AYUSH, Govt. of India for providing financial assistance. The study was undertaken in joint collaboration between CIRE, Kolkata and CCRH, New Delhi.

Financial Support and Sponsorship

Central Council for Research in Homoeopathy, New Delhi.

Conflicts of Interest

There are no conflicts of interest.

 
  References Top

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Yao SH, Dang ZM, Jiang MJ, Xu HP, Bai JB. Influence of aspect ratio of carbon nanotube. On percolation threshold in ferroelectric polymer Nano composites. Appl Phys Lett 2007;91:212901.  Back to cited text no. 10
    
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Thakur P, Kool A, Bagchi B, Das S, Nandy P. Effect of in situ synthesized Fe2O3 and Co3O4 nanoparticles on electroactive ß phase crystallization and dielectric properties of poly(vinylidene fluoride) thin films. Phys Chem Chem Phys 2015;17:1368-78.  Back to cited text no. 11
    
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He F, Lau S, Chan H L, Fan J. High dielectric permittivity and low percolation threshold in nano composites based on poly (vinylidene fluoride) and exfoliated graphite nanoplates. Adv Mater 2009;21:710-5.  Back to cited text no. 14
    
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Thakur P, Kool A, Bagchi B, Das S, Nandy P. Enhancement of β phase crystallization and dielectric behavior of kaolinite/halloysite modified poly (vinylidene fluoride) thin films. Appl Clay Sci 2014;99:149-59.  Back to cited text no. 15
    
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Nandy P. A review article of basic research on homeopathy from a physicist's point of view. Indian J Res Homoeopathy 2015;9:141-51.  Back to cited text no. 16
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Halder K, Paul BK, Bagchi B, Bhattacharya A, Das S. Copper ion doped mullite composite in poly (vinylidene fluoride) matrix: Effect on microstructure, phase behavior and electrical properties. J Res Updat Polym Sci 2014;3:157-169.  Back to cited text no. 20
    
21.
Paul BK, Halder K, Roy D, Bagchi B, Bhattacharya A, Das S. Dielectric switching above a critical frequency occurred in iron mullite composites used as an electronic substrate. J Mater Sci Mater Electron 2014;25:5218-25.  Back to cited text no. 21
    
22.
Thakur P, Kool A, Bagchi B, Hoque NA, Das S, Nandy P. In situ synthesis of Ni(OH) 2 nanobelt modified electroactive poly (vinylidene fluoride) thin films: Remarkable improvement in dielectric properties. Phys Chem Chem Phys 2015;17:13082-91.  Back to cited text no. 22
    
23.
Thakur P, Kool A, Bagchi B, Hoque NA, Das S, Nandy P. Improvement of electroactive β phase nucleation and dielectric properties of WO3H2O nanoparticles loaded poly (vinylidene fluoride) thin films. RSC Adv 2015;5:62819-27.  Back to cited text no. 23
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]


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