The effect of various substituents in donor moiety on the aggregation of nonlinear-optical quinoxaline-based chromophores in composite polymer materials

Abstract

A series of substituents of various types in chromophore donor moiety in ortho- and meta-positions relative to divinylquinoxaline π-electron bridge was examined for isolating ability, preventing the dipole chromophores antiparallel detrimental aggregation in polymer matrix. The study was performed by molecular modeling of PMMA-based composite polymer materials with different content of pristine chromophore with dibutylaniline donor, divinylquinoxaline π-electron bridge and tricyanofuran acceptor (I) in the range from 10 wt% to 30 wt%, and of composite polymer materials with 30 wt% load of chromophores with various isolating groups of aryl, alkyl and mixed nature in donor moiety. The effect of the substituents in donor groups on the molecular nonlinear-optical (NLO) characteristics of chromophores – first hyperpolarizability – was estimated by quantum-chemical calculations at DFT level with M06-2X density functional. Introduction of isolating group in meta-position of donor is shown to lead to a strong decrease of the first hyperpolarizability of a chromophore compared to that of pristine chromophore. Joint consideration of results of molecular modeling and quantum-chemical calculations allows one to nominate o-ethyl, o-benzyloxyhexyloxy and m-methoxy-o-phenyl groups to be the best isolating ones.