<p>The current study investigates the photocatalytic degradation of Rhodamine B (RhB) dye using polymethyl methacrylate (PMMA) doped with copper oxide (CuO) nanoparticles (NPs) under UVc light, synthesized via a casting technique. The structural, thermal, and morphological properties of the nanocomposites were examined using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The XRD analysis revealed an average crystallite size of nearly 45 nm for CuO NPs. FTIR spectroscopy confirmed the interaction between CuO and PMMA by observing shifts in PMMA’s infrared peaks. The incorporation of CuO NPs reduced the optical bandgap, suggesting the formation of intermediate energy bands. SEM images indicated significant PMMA surface morphology changes due to CuO NPs dispersion. Adding CuO enhanced the thermal stability of PMMA, while dielectric measurements showed a decrease in ε’ and the loss tangent (tan δ) with increasing frequency. Furthermore, increasing CuO content led to higher AC electrical conductivity. The CuO/PMMA nanocomposites exhibited a photocatalytic degradation efficiency of 97.4% and a reaction rate constant of 0.031 in the degradation of RhB dye, attributed to the increased surface area of the nanocomposites that aids in capturing dye molecules. These results demonstrate that CuO/PMMA films are effective, environmentally friendly catalysts for treating organic pollutants in water and wastewater, with enhanced photocatalytic activity driven by the synergy between CuO NPs and the PMMA matrix.</p> Graphical abstract <p></p>