Exploring crystallinity, free volume and optical energy band gap effects on nonlinear optical properties of P(MMA-co-MA)/NiO and P(MMA-co-MA)/CuO polymer nanocomposites

Polymer nanocomposites (PNCs) of poly(methylmethacrylate-co-methacrylic acid) (P(MMA-co-MA)) / Nickel Oxide (NiO) and P(MMA-co-MA)/Cupric Oxide (CuO) (with 0.2, 0.4, 0.6, 0.8 and 1 wt% of nanofillers) have been prepared to explore the microstructural-dependent nonlinear optical (NLO) properties. The microstructure of PNCs are characterized using Positron Annihilation Lifetime Spectroscopy (PALS), Scanning Electron Microscopy (SEM), powder X-ray Diffraction (XRD), UV–Visible spectroscopy and Z-scan techniques to investigate their structural, optical and nonlinear properties. A noticeable decrease in the optical energy band gap at 0.4 wt% of NiO nanofiller and 1.0 wt% of CuO nanofiller loading, attributed to reduced crystallinity, which is confirmed by XRD results. PALS measurements reveales the presence of bigger free volume holes, which facilitate dipole polarization and significantly boost NLO performance. The findings demonstrate that P(MMA-co-MA)/NiO and P(MMA-co-MA)/CuO PNCs exhibit tunable NLO characteristics.