Structure, morphology, and optical properties of polyacrylamide/poly (vinyl alcohol) (PAM/PVA) polymer blend containing MnO₂ nanoparticles at different concentrations

Abstract

Manganese Dioxide (MnO2) nanoparticles were incorporated into a Polyacrylamide/Polyvinyl Alcohol (PAM/PVA) polymer blend via solution casting to investigate the influence of MnO2 content (0.1, 0.5 and 1.0 wt%) on the composite’s structural and optical behavior. The novelty of this work lies in demonstrating that the incorporation of very low MnO2 concentrations effectively modifies the optical properties of the PAM/PVA blend while preserving its structural integrity through strong interfacial interactions, providing an efficient strategy for tuning polymer nanocomposite performance. X-ray diffraction confirmed the semi-crystalline nature of PAM/PVA blend and successful incorporation of MnO2 nanoparticles without altering the polymer matrix, while Fourier transform infrared (FTIR) spectroscopy indicated strong interfacial interactions between the polymer matrix and MnO2 surface species, suggesting the presence of chemical bonding and modified local electronic environments. Scanning electron microscopy (SEM) and energy- dispersive X-ray (EDX) mapping demonstrated uniform nanoparticle dispersion at low concentrations and the emergence of agglomeration at higher concentrations, with corresponding changes in surface morphology. UV–Vis spectroscopy indicated progressively enhanced absorption and a systematic reduction in the optical band gap from 4.27 eV (pristine) to 4.00 eV (1 wt.%MnO2), accompanied by an increase in the refractive index. The tunable optical response of PAM/PVA–MnO2 nanocomposites highlights their potential for applications in flexible optoelectronics, sensors, and energy storage devices.