Linear and nonlinear optical parameters of biodegradable chitosan/polyvinyl alcohol/sodium montmorillonite nanocomposite films for potential optoelectronic applications
Mahdy M. Elmahdy, Mohamed A. Yassin
Abstract
Innovations in sophisticated optoelectronic devices have increased interest in high-refractive index polymers. Herein, we report innovative nanocomposite films with high linear and nonlinear refractive indices prepared by casting chitosan (Cs) with polyvinyl alcohol (PVA) (50:50 wt%) along with different concentrations (10–50 wt%) of sodium montmorillonite (NaMMT) nanoclay . The refractive indices in addition to other optical parameters of homopolymers and hybrid materials were investigated by UV–Vis. spectroscopy and optical modeling to assess their potential applications in optics . Besides, the structure, morphology, and thermal stability of the prepared films were investigated by a multitude of experimental techniques including X-ray diffraction (XRD), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), and thermogravimetric analysis (TGA/DTG). The ATR-FTIR, XRD, SEM, and AFM measurements confirmed the complete exfoliation of NaMMT nanolayers in the Cs/PVA matrix. The TGA/DTG revealed an increase in the thermal stability of Cs/PVA film with increasing clay content. The UV–Vis. measurements revealed a decrease in the optical energy gap ( E g ) and a substantial increase in the linear ( n D ) and nonlinear ( n 2 ) refractive indices as clay content increased. Additionally, the nanohybrids displayed low UV transmission and reflected about 80 % of UV rays, making them excellent candidates for UV protection. For the first time, the dissipation factor (tan δ ) in the UV/Vis. region has been calculated and fitted with the Drude-Lorentz model to predict the plasma frequency ( ω p ), resonance frequency ( ω 0 ), and electron lifetime ( τ ) of pristine polymers and nanocomposites.