Tailoring the Optical, Electrical, and Dielectric Characteristics of PEG/PVA Blends by Integrating MWCNTs to Enhance the Performance of Advanced Energy Storage Devices

Abstract

In the context of developing and encouraging flexible energy storage applications and optoelectronic devices, the influence of multiwalled carbon nanotubes (MWCNTs) on structural, optical, dielectric, and electrical characteristics of polyethylene glycol/poly(vinyl alcohol) (PEG/PVA) blends has been studied. TEM imaging confirms that MWCNTs are elongated nanotubes with multiple concentric graphene layers, typically 20–22 nm in diameter. XRD studies showed that, after MWCNTs were added , the crystallinity of the polymeric matrix decreased, whereas the amorphous content increased, ensuring significant optimization of electrical conductivity. Strong interactions between MWCNTs and the polymer matrix have also been detected by FTIR spectroscopic analysis through the shifting of absorption bands and the variation in the intensity of functional groups. Optical characterization exhibited tunable absorption properties and narrowed band gap, while the increased concentration of MWCNTs facilitated the formation of charge-transfer complexes, which enhanced electronic conductivity of the present samples. This is evidenced by the reductions in both the indirect and direct optical band gaps. For the pure PEG/PVA matrix, the indirect and direct optical band gaps were 4.24 and 4.88 eV, respectively. However, with the addition of 1.2 wt % MWCNTs these optical band gaps decreased significantly to 3.05 eV (indirect) and 4.36 eV (direct). Dielectric studies showed an improvement in electrical permittivity with reduced interfacial polarization losses. The maximum AC conductivity was observed at 1.2 wt % MWCNTs, reaching a value of 1.45 × 10^–6 S/cm at room temperature. This enhancement in conductivity is attributed to the formation of interconnected MWCNT networks within the polymer matrix, which effectively lowers the energy barriers for charge transport and promotes efficient electron mobility. Impedance spectroscopy and Nyquist plots showed a considerable reduction in bulk resistance, reflecting the increased conductivity and energy storage potential. An electrical equivalent circuit was presented for each sample based on the fitting curves of the impedance spectroscopy data. Specific research findings indicated that the PEG/PVA/MWCNTs nanocomposites exhibited promising properties for the next generation of flexible electronics, storage, and optoelectronic appliances. This work provided a deep understanding of how MWCNTs doping inherently influences polymer nanocomposites and could be of great importance to designers in engineering modern advanced functional material systems.