**3. Results and discussion**

**Figure 4** reveals the energy dispersive spectra of the prepared samples. From these spectra, the chemical composition of composite materials can be explained. *Structural, Optical, and Electrical Studies of PAN-Based Gel Polymer Electrolytes… DOI: http://dx.doi.org/10.5772/intechopen.98825*

#### **Figure 4.**

*[a-d]. EDS spectra of PAN:NaF (70:30) + (1–4)Wt% Al2O3 nanocomposite gel polymer electrolyte films.*

The analysis indicates the presence of carbon (C), nitrogen (N), sodium (Na), fluoride (F), oxygen (O), and aluminum (Al) with chemical elements in the GPE of PAN + NaF (70:30) **+** Wt% Al2O3. EDS can be used to estimate the relative abundance and accuracy of quantitative analysis. This analysis explains the structural properties of prepared samples, and these properties may affect various factors [6–8]. With increasing nanofillers in the polymer composite, the atomic nature of the samples can be modified, and the results are represented in the above tabular forms.

## **4. UV: Visible spectroscopy**

**Figure 5** shows the UV–Vis spectra of PAN with different wt. % ratios of NaF salt and Al2O3 nanoparticles at room temperature**.** The UV–Vis spectrum was recorded by a Hewlett-Packard HP8452A diode array spectrometer. The structural effect of salt and nanoparticles on the conductivity was also confirmed by UV–Vis spectroscopy. Optical absorption, particularly studying the shape and shift of the absorption edge, is a useful technique for understanding the basic mechanism of optically induced transitions in crystalline and noncrystalline materials. UV–Vis

**Figure 5.** *(a-e): UV–VIS spectroscopic images of PAN:NaF (70:30) and different ratios of nanoparticle gel polymer electrolyte films at room temperature.*

spectroscopy is used to identify inorganic complexation of molecules and their qualitative and quantitative measurements [9]. It is also used to identify the energy band gap values of the materials in the transmitting radiation. At an energy level, a photon is absorbed in its orbit. When an electron jumps from a lower energy level to a higher energy level. Transitions take place in a band gap energy as it rises in the absorption process called the absorption edge, where the optical band gap energies are determined [10–12]. The absorption rate is slightly changed by increasing the salt ratio of solvents and nanoparticles. The optical band gap of the polymer electrolytes was determined using UV–Vis spectra. It can be determined by

$$\mathbf{E} = \mathbf{h}\mathbf{c} / \mathcal{X} \tag{1}$$

where h is Planck's constant (6.626 x 10−34 joules sec), c is the light velocity (3 x 108 meters/sec), and λ is the cutoff wavelength. **Table 2** gives the wavelength values from the UV–Visible spectra. It is cleared that the optical energy band.

#### **4.1 DSC characteristics**

The Mettler instrument was calibrated with indium and zinc standards and the analyses were conducted under a nitrogen flow rate of ca. 20 mL/min. The sample was heated sequentially from 50–360°C. The change in transition temperature caused by the incorporation of nanofiller Al2O3 and plasticizer into the PAN+NaF complex was studied by DSC analysis. **Figure 6** shows the DSC thermograms of 70PAN:30NaF and 1–4 wt% Al2O3.

**Polymer electrolyte Planck's constant (h) Light velocity (C) Wavelength (**Ǻ**) Optical energy band gap in (ev) Pure PAN** 6.626 x 10−34 joules sec 3 x 108 meter/ sec 350.12 3.54842 70PAN:30NaF:1 wt% 6.626 x 10−34 joules sec 3 x 108 meter/ sec 340.0 3.65404 70PAN:30NaF:2 wt% 6.626 x 10−34 joules sec 3 x 108 meter/ sec 352.0 3.52787 70PAN:30NaF:3 wt% 6.626 x 10−34 joules sec 3 x 108 meter/ sec 360.0 3.44803

3 x 108

 meter/ sec

350.0 3.54947

*Structural, Optical, and Electrical Studies of PAN-Based Gel Polymer Electrolytes… DOI: http://dx.doi.org/10.5772/intechopen.98825*

#### **Table 2.**

*Optical energy band gap for PAN-based polymer electrolytes.*

joules sec

70PAN:30NaF:4 wt% 6.626 x 10−34

#### **Figure 6.** *DSC thermographs of the 70PAN:30NaF, A1, A2, A3, and A4 samples.*

**Table 3** summarizes melting temperature (Tm) and the corresponding heat enthalpy (ΔHm) and the percentage of crystallinity (χc) of the prepared polymer electrolytes. The percentage of crystallinity was calculated by

$$\chi\_{\rm c} = \Delta \text{H}\_{\rm m} \, ^\ast / \Im \mathfrak{B} \mathfrak{B} . \text{\(\text{\(\beta\)}\)}{\text{\(\beta\)}} \tag{2}$$

where ΔHm\* is the heat enthalpy of the polymer electrolytes, PAN has Tm,Tg and ΔHm of 317°C, 107°C, and 398.6 Jg−1respectively. From the table, it can be concluded that the


**Table 3.**

*Tm,* ∆*Hm \* ,* χ*c of 70PAN:30NaF, A1, A2, A3, A4 samples.* incorporation of NaF salt and Al2O3 nanopowder into the polymer blend matrix decreases the Tm value, and the minimum Tm value is 283.42°C for the 3 wt.% Al2O3 nanopowder content. This observation suggests an increase in the crystallinity of the complexes because of the presence of excess nanopowder. It is also evident from conductivity studies that the conductivity of the complexes increases with increasing salt concentration and decreases for greater concentrations of nanopowder due to the formation of ion clusters. When sodium fluoride salt was added to the host polymer PAN, the results obtained indicated that the filler–polymer interaction influenced the speed of sodium ions in the polymer chain. This is in good agreement with TGA results [5, 13–16].
