Controlling the structural, optical, and dielectric properties of PVP/NaAlg-MWCNT flexible nanocomposites for next-generation electronics

In this study, nanocomposites based on polyvinylpyrrolidone (PVP) and sodium alginate (NaAlg) in a 30/70 wt% ratio were successfully prepared using the solution casting method and reinforced with multi-walled carbon nanotubes (MWCNTs). The effect of MWCNT incorporation on the structural, optical, dielectric, and electrical properties of the pristine PVP/NaAlg blends was comprehensively investigated. XRD patterns showed that the incorporation of MWCNTs enhanced the amorphous nature of the polymeric blend. Fourier transform infrared (FTIR) spectra showed the characteristic vibrational bands of PVP and NaAlg, with noticeable shifts and intensity changes upon MWCNT loading, suggesting strong interfacial interactions. These interactions are attributed to hydrogen bonding between PVP (C = O) and NaAlg (–OH, –COOH) groups, in addition to π–π stacking and dipole–π interactions with MWCNTs. UV–vis spectroscopy demonstrated a gradual increase in optical absorption accompanied by a redshift, consistent with improved light-harvesting capability. The optical band gap decreased from 4.25 to 2.73 eV (indirect) and from 5.01 to 4.68 eV (direct). Moreover, both AC and DC conductivities, as well as dielectric properties, increased with higher MWCNT concentrations, evidencing enhanced charge transport and polarization behavior. The DC conductivity rose from 2.00 × 10⁻¹⁰ to 1.15 × 10⁻⁵ S·cm⁻¹, while the dielectric constant increased from 10 to 1.15 × 10⁵, reflecting the remarkable energy storage capability of the prepared films. The electrical conduction process follows the correlated hopping mechanism. These findings highlight the potential of PVP/NaAlg–MWCNT nanocomposite films as promising candidates for next-generation optoelectronics and energy storage applications.