The Layer-by-Layer Self-Assembled Pyrroline-Based Donor-Acceptor Chromophores

The layer-by-layer self-assembly of high-β pyrroline-based donor-acceptor (or push-pull) chromophores has been developed because of the increasing needs in the information technology fields for higher capacity and bandwidth. Efficiently organizing molecular nonlinear optical (NLO) chromophores having large first-order hyper-polarizabilities (β) into acentric microstructures for electro-optic (EO) applications represents a significant materials synthesis and processing challenge, in part due to inter-chromophore dipolar interactions that promote centro-symmetric organization. Our Research Goal is to successfully produce the formation and characterization of a self-assembled tricyanopyrroline-based nonlinear optical (NLO) chromophore into intrinsically acentric superlattices. The chromophore superlattices are assembled on clean glass of ITO-coated glass substrates following the iterative reaction sequence: (i) treatment with iodopropyltrimethoxy silane (IPTMS) to provide a coupling layer; (ii) quaternization of 2-({4-[(E)-2-[4-cyano-5-(dicyanomethylidene)-2-oxo-1H-pyrrol-3-yl]ethenyl]phenyl}(methyl)amino)ethyl 3-(pyridin-4-yl)propyl carbonate to form  a (tricyanopyrroline)pyridinium chromophore layer; (iii) reaction with diiodohexane to form a linking layer or IPTMS to form a scaffolding/linking layer.  Layer deposition will be monitored via UV-VIS spectroscopy by observing the growth of the absorption peak at 585nm±5nm.  Chromophore superlattices will be characterized by atomic force microscopy and polarized second harmonic generation (SHG). This is still a work in progress, so there is no meaningful results as of yet, for the experiment is currently running. By developing better electro-optic materials, we can power the optical networks that future generations will require as we will be able to more efficiently transcode electrical and optical signals. Through our research we hope to refine previously developed methods of self-assembly and further push the advancement of electro-optic materials.