Holographic and diffraction patterns of Schiff base liquid crystal-doped PMMA polymer

The scope of our research encompasses is the preparation of a liquid crystalline compound with a low molecular weight through the process of direct alkylation of para-pentyloxy benzaldehyde. The effect of the bromo terminal group on the optical properties of pure nematic liquid crystals (LCs) was investigated and studied the effect of changes in the molecular shape on some physical parameters, such as optical transmittance and activation energy as well as dielectric anisotropy. Based on the results of optical transmittance measurements as a function of temperature and bias voltage, the LC seems to possess an anisotropic character. FTIR spectrophotometer was conducted to investigate the molecular structure and differential Scanning Calorimeter (DSC) was used to characterize the mesomorphic characteristics of the molecules as well as the polarizing microscopy (POM) used to show the optical texture of the samples as they transition from the isotropic phase to the nematic phase. Two helium–neon lasers with different wavelengths (λ = 612 nm and 543.5 nm) were chosen to study the holographic properties of azo-dye methyl red (MR)/Schiff base LC-doped Poly(methyl methacrylate) (PMMA) film. The diffraction efficiency was 5.812% for the first order. The nonlinear refractive index (NRX) for randomly orientated azo-dye MR/Schiff base LC-doped PMMA films was measured by counting the number of rings seen by a diffraction technique and is found to be the order of (0.5–4.51) × 10⁻⁵ cm²/W for (0.3–0.55) doping ratios respectively. We have replicated the diffraction patterns using a well-known theoretical model based on wave theory. The results have been shown the reasonable agreement between the theoretical model and the experimental results.