Modeling of Structure and Nonlinear Optical Activity of Epoxy‐Based Oligomers with Dendritic Multichromophore Fragments

Abstract

AbstractSummary: Epoxy‐based oligomers having length up to four units with dendritic chromophore‐containing fragments covalently attached through spacers to the bearing chain are studied. The structure of the oligomers was obtained in the course of conformational search by Monte‐Carlo method, the distribution of the torsion angles values in the dendritic fragment was examined by molecular dynamics. The nonlinear‐optical response of the studied oligomers and dendritic chromophore fragments was calculated by the TDHF method at AM1 level. Intradendron cross‐linking of chromophore groups is investigated, diphenylmethandiisocyanate used as hardening agent. Cross‐linking is shown to decrease the angles between the chromophores in the dendron, thus providing enhanced nonlinear‐optical characteristics of the oligomer. Stacking‐like arrangement of chromophore groups, observed in variety of oligomers, is investigated in the framework of topological analysis of electron charge density, and Van‐der‐Waals interactions are found to be responsible for the stacking effect.