Analysis of Spectroscopic, Optical and Magnetic Behaviour of PVDF/PMMA Blend Embedded by Magnetite (Fe3O4) Nanoparticles

In the present work, magnetite (Fe3O4) nanoparticles have been prepared by a simple chemical method. Polymer nanocomposites based on the blend between poly vinylamine fluoride (PVDF) and (methyl methacrylate) (PMMA) doped with different concentrations of Fe3O4 nanoparticles have been prepared. The structural, optical, and magnetization properties of the nanocomposite samples were studied using suitable techniques. The X-ray study reflected that the cubic spinal structure of pure Fe3O4 crystal. No small peaks or ripples were found in the X-ray spectra, conforming to good dispersion of Fe3O4 within PVDF/PMMA matrices. The FT-IR analysis demonstrated the miscibility between the PVDF and PMMA blend with the interaction between the polymer blend and Fe3O4. The values of the band gap from UV-Vis study were decreased up to 4.21 eV, 3.01 eV for direct and indirect measurements, respectively. The magnetization was measured as a function of the applied magnetic field in the range of −2000 2000 Oersted. The curves of the magnetization indicated a paramagnetic behavior of pure Fe3O4 nanoparticles and PVDF/PMMA-Fe3O4 nanocomposites. The values of saturation magnetization for pure Fe3O4 are nearly 75 emu/g, exhibiting a paramagnetic behavior, and it is decreased with the increase of Fe3O4 content.


Introduction
Polyvinylidene fluoride (PVDF) is known as one of semi crystalline polymer [1] [2]. PVDF is characterized by its wide applications because of its excellent and extraordinary properties like smart mechanical strength, and high thermal stability [3] [4]. PVDF is a good response to the piezoelectric and pyroelectric properties. PVDF polymer has at least four polar phases known as (α) alpha, (β) beta, (γ) gamma, and (δ) delta phases. Due to the presence of these phases, PVDF is used to enhance and develop the electronic devices and sensors applications [5] [6]. Different pairs of polymer blends between PVDF and other polymers are examined by several authors, like PVDF/polyvinylpyrrolidone (PVP) [7] [8], PVDF/polyethylene glycol (PEG) [9] [10], PVDF/poly vinyl acetate [11], PVDF/polymethyl methacrylate (PMMA) [12] [13]. As an example of those blends, PMMA is considered one of the most interesting polymers because of its good compatibility with PVDF.
The changes in the structural and morphological PVDF/PMMA polymer blend prepared by different methods are studied by Kim et al. [14]. When PVDF/PMMA is prepared by melting technique, the reducing rate of crystallization after adding PMMA prefers the crystal phase formation and the phase formation is reduced. However, when PVDF/PMMA is prepared by the casting method, the addition of PMMA had little effect on the crystalline phases. However, Zhang et al. showed that the crystallization behaviour of the PVDF/PMMA blend is highly dependent on the components of mixed solutions [15]. They observed that the phases of PVDF are clear when the weight ratio of PVDF is higher than 30 wt% and the adding of 10 wt% of PMMA could help the growth of PVDF crystallization [16]. The PVDF/PMMA blend is thought to result from the interaction between the oxygen atom of the carbonyl groups in PMMA and the hydrogen atom in PVDF [17] [18]. Magnetite nanoparticles (Fe 3 O 4 ) have attracted increasing interest within the fields of applied nanoscience and technology attributed to their unique and new physicochemical properties that are achieved according to their particle size, shape morphology, and shape of geometric films. Various methods of preparation of magnetite nanoparticles were performed through several techniques, including co-precipitation showing that the addition of nanoparticles to the polymer and/or polymer blend may enhance compatibility between the polymers. Magnetite nanoparticles (Fe 3 O 4 ) are one of most nanoparticles to improve and enhance the magnetic properties for polymer nanocomposites in the industry [19] [20].
Pure blend without nanofiller between PVDF and PMMA blends have been prepared and investigated by FT-IR spectroscopy, X-ray, and thermal analysis [21]

Synthesis of Magnetite Nanoparticles (Fe 3 O 4 )
The magnetite nanoparticles (Fe 3 O 4 ) were synthesized using the promising methods because of its simplicity and ease of implementation with less hazardous and fewer procedures. Ferric chloride (FeCl 3 ·6H 2 O) and ferrous chloride (FeCl 2 ·4H 2 O) were mixed using 2:1 molar ratio. The ferric solutions of both Fe 2+ and Fe 3+ were prepared by making their aqueous solutions in distilled water. Then the solutions were heated at 50˚C for about 10 min. After heating the solutions, it will be deposited in the presence of an ammonia solution (NH 4 OH) with constant stirring by the magnetic stirrer at 50˚C. It is also known that the nanocomposite polymeric solution is more stable when ammonium was added. Black color particles of magnetite nanoparticles are deposited. These nanoparticles are then separated from the solution using a strong magnet and washed several times with distilled water. Black magnetite deposits remain. The powder was then dried in a hot air oven at 100˚C overnight. General reaction can be written as the following reaction:

Preparation of PVDF/PMMA-Fe 3 O 4 Nanocomposite Films
Polyvinylidene fluoride (PVDF) pellet (4.0 g/50ml) and polymethyl methacrylate (PMMA) powder (4.0 g/50ml) were dissolved individually in tetrahydrofuran (THF) as a common solvent for the polymers at 60˚C Pure solution of PVDF/PMMA was mixed and it stirred using magnetic stirrer about 4 hours at the same temperature. We followed the methods of authors to prepare the polymer blend nanocomposites containing nanoparticles [25]

Characterization Techniques
The X-ray diffraction (XRD) of the nanocomposites films were carried out by PANalytical X'pert Pro MPD diffractometer with Cu-Kα radiation (λ = 1.5406 Å) at operating voltage 15 kV over the range of 2θ = 5˚ -80˚. The complexation between nanocomposites (PVDF/PMMA-Fe 3 O 4 ) was studied using Fourier transform infrared (FT-IR) spectroscopy (FTIR-430, Jascow, Japan) at wavenumber range of 4000 cm −1 -400 cm −1 . The UV-Vis spectra were recorded by a spectrophotometer (V-570 UV/VIS/NIR, Jasco, Japan) in the frequency range of 190 to 1000 nm. The magnetization curves of the PVDF/PMMA-Fe 3 O 4 nanocomposite films were measured using VSM measurement at room temperature (25˚C).

X-Ray Measurements
The crystalline structure of PVDF/PMMA films doped with different contents (0, 0.4, 0.8 and 1.2 wt%) of magnetite nanoparticles (Fe 3 O 4 ) is recorded using X-ray diffraction as shown in Figure 1. The main X-ray peaks of pure Fe 3 O 4 powders are founded and inserted in Figure 1. The X-ray spectrum exhibited peaks corresponding to (220), (311), (400), (422), (511) and (440) [27] [28] are reflects to Fe 3 O 4 crystal with the cubic spinal structure. The X-ray diffraction measurements of PVDF/PMMA show the semicrystalline structure [29] as the hump and broad peak recorded at 2θ = 18.38˚ with a peak at 2θ = 39.07˚. From the spectra of PVDF/PMMA films, no ripples and/or small peaks are found, indicating that the Fe 3 O 4 has a good distribution in PVDF/PMMA blend. The movement of the position for Bragg angles from 2θ = 18.38˚ to 2θ = 20.04˚ are founded confirms that the crystal structure of Fe 3 O 4 is altered by its inserted within PVDF/PMMA matrices. A small decrease in the hump at 18.38˚ after adding the Fe 3 O 4 is seen suggesting that the amorphicity increased. An increase of the hump causes an increase of the amorphous nature inside the nanocomposite films according to Hodge et al. method [30]. The interaction between the PVDF/PMMA blend and Fe 3 O 4 causing a decrease in the degree of crystallinity of the films. This demonstrating that complexation between Fe 3 O 4 and PVDF/PMMA takes place in the amorphous region [31]. The amorphous nature is responsible for the higher conductivity behavior of the prepared samples.

FT-IR Analysis
The FT-IR spectra of PVDF/PMMA blend doped different concentrations of   is assigned to CF 2 asymmetric stretching mode since CF 2 group is absorbed strongly in the region of 1120 -1350 cm −1 . The C-C-C asymmetrical stretching vibration band is observed at 880 cm −1 . The absorption band at 796 cm −1 corresponds to CF 2 skeletal vibration mode. The absorption band at 478 cm −1 corresponds to CF 2 bending vibrational mode [32]. The assignments of FT-IR spectrum of PVDF have been reported as follows: α-phase bands due to CF 2 bending are observed at 482 cm −1 , 531 cm −1 and 615 cm −1 . The main bands ascribed to CH 2 wagging broad mode are observed at 1062 cm −1 , whereas the β-phase band due to CF 2 symmetric. The presence of the absorption band at 1729 cm −1 is attributable to the stretching of the carbonyl group of PMMA in the blend samples.
The FT-IR spectrum of pure magnetite nanoparticles is inserted inside Figure  2. For the magnetite, the band at 580 cm −1 corresponds to the vibration of the Fe-O bonds. Additionally, the bands at 1633 and 3400 cm −1 can be attributed to the stretching vibration of the hydroxyl groups on the surface of the magnetite nanoparticles [33]. The FT-IR spectra of the nanocomposite are found partially changed after the addition of Fe 3 O 4 with a decrease or disappear of some IR bands. These results conform to an interaction between the Fe 3 O 4 nanoparticle, and the polymer blend has occurred.  The spectrum of pure PVDF/PMMA polymer blend shows an absorbance band at 219 nm attributed to the n → π* transition. Moreover, the spectrum displays the sharp edge which towards to red shifted from 219 nm to 241 nm as an increase of absorbance values for doped the films by the Fe 2 O 3 nanoparticles, where the color of films is changed from the transparent color to pinkish red. These observations demonstrate that the link between the Fe 2 O 3 nanoparticles with the functional groups in the PVDF/PMMA and caused a change of the band gap energy.

UV-Vis Analysis
The estimated values of E g for PVDF/PMMA-Fe 2 O 3 nanocomposite films can be determined by [34] [35] [36]: where, α is the absorption coefficient, hν is the photon energy, B is a constant.
The values of n are equal to 1/2 for allowed direct and it is equal to 2 for allowed indirect allowed transitions. The absorption coefficient (α) was determined from the equation:       [41]. This is mainly because Fe 3 O 4 nanoparticles are embedded into a nonmagnetic polymer matrix. With the decrease in the Fe 3 O 4 content, the magnetic saturation value also decreases. These results suggest that the paramagnetic behavior observed in the nanocomposites arose from the magnetic Fe 3 O 4 nanoparticles attributed to the decreasing tendency of the nanoparticles to aggregate on decreasing their content. Due to the magnetic properties of the prepared nanocomposites, the magnetic composite films can be further exploited for magnetic applications [42].

Conclusion
New nanocomposite films consist of PVDF/PMMA blend loaded by different concentrations of magnetite nanoparticles (Fe 3 O 4 ) using the casting method. The change of the structural, optical, magnetization properties of these nanocomposites has been studied in detail. The structural and chemical complexations between the components were characterized by XRD and FT-IR measurements. The X-ray spectra display the semicrystalline structure of all samples with a decrease of the crystalline degree as an increase of Fe 3 O 4 contents. Further, the X-ray spectrum exhibited some peaks that are reflected in the cubic spinal structure of the nanocomposites with good dispersion of Fe 3 O 4 nanoparticles within PVDF/PMMA. The FT-IR spectra confirm the miscibility between the PVDF/PMMA blend and show the chemical interaction between the polymer blend and

Conflicts of Interest
The author declares no conflicts of interest regarding the publication of this paper.