Determination of the macroscopic optical properties for composite materials

Abstract

The effect of polymeric matrix on the linear and nonlinear optical (NLO) property of disperse red (DR1) molecule embedded into poly(methyl methacrylate) (PMMA) is discussed. The performed study is devoted to the simulations of the molecular polarizabilitities α and β(2 ω;ω,ω) in vacuum and in polymer using local field approach. The structure of the investigated system has been modeled by molecular dynamic simulations applying molecular mechanic CVFF force field method. The obtained structural data are typical of amorphous structure. Investigations of radial distribution function prove that location of chromophores in polymeric matrix is an intrinsic property of polymer. The motion of polymer chain allows a rotation of dopants under influence of an external electric field. The averaged modeled structural data were taken into account to compute the changes of chromophores optical properties affected by environment. Quantum chemical time-dependent density functional theory (TDDFT) calculations of the first-order nonlinear optical properties were performed. The local electric field computed using point dipole moment approach is significant; however the obtained results show a small effect of PMMA on linear optical property of DR1. The effect of local electric field is more pronounced for the first hyperpolarizability. PMMA matrix is appropriate for DR1 as host polymer because of high stability of beck relaxation but not good from electronic intra-molecular interaction which cancels NLO property of chromophore.