Monte Carlo kinetic study of chromophore distribution in poled guest-host system
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The origin of a strongly nonlinear dependence of second order nonlinear optical properties of poled thin films of a guest-host system consisting of charge transfer chromophores in a polymer matrix, on concentration of chromophores, remains unknown. Recently Rau et al.1, 2 have provided evidence based on optical microscopy in favor of a new mechanism of relaxation due to an accelerated chromophore aggregation during the heating which facilitates chromophore diffusion. Aggregation is an important factor which decreases the susceptibility. Kinetic Monte Carlo technique is used for a study of a poled guest-host system (polymer matrix with dipoles) to analyze the local free volume distribution which determines the ability of a dipole to reorient. The simulations show a large degree of inhomogeneity in this parameter, which results in a jamming effect for both orientational and translational diffusion of the dipoles. The applicability of point dipoles approach at high loads is critically discussed. The emerging physical picture of the poling allows an interpretation in terms of an aggregation observed by Rau et al.
[1] D. Griffiths. Introduction to Electrodynamics , 2017 .