Poled Polymeric Nonlinear Optical Materials. Enhanced Second Harmonic Generation Temporal Stability of Epoxy-Based Matrixes Containing a Difunctional Chromophoric Comonomer

The long-term orientational stabilization of nonlinear optical (NLO) chromophores which have been preferentially aligned within a polymeric medium by electric field poling represents a crucial test of the extent to which polymer relaxation/physical aging can be controlled chemically and is of paramount importance to the development of efficient polymer-based second-order NLO materials.¹ We recently reported² an effective approach to chromophore immobilization which utilizes electricfield-induced alignment of high-β_vec chromophores dispersed within a two-component epoxy matrix³ which is concurrently subjected to thermal cross-linking.⁴ The chromophores are found to exhibit higher levels of orientational stability within the cross-linked matrix, as evidenced by significantly improved second harmonic generation (SHG) temporal stability. Nevertheless, the SHG efficiency of such guest-host systems is severely limited by the low chromophore number densities and still less than optimum chromophore immobilizations which are practicable.^{2, 5} We communicate here the synthesis and implementation of a second generation epoxy-based NLO chromophore system in which a reactive high-β_vec chromophore serves as both the NLO-active component and as the diamine cross-linking agent of the matrix (Scheme I). We also demonstrate that the SHG temporal stability of such materials can be enhanced significantly by employing an oligomeric epoxide reagent.