Self-assembly of nonlinear optical chromophoric layers through the ionic interaction

The ionic attraction was applied to construct nonlinear optical (NLO) chromophoric layers. In order to fully utilize such an interaction, stilbene-type NLO chromophores having an anionic group at one end of the chromophores were designed. Among such type of the chromophores, trans-4′-(4-sulfonic acid sodium salt)butanoxystyrylpyridine (1) was synthesized. The pyridine moiety of the chromophore can be easily methylated to augment the molecular hyperpolarizability (β). The above anionic chromophore self-assembles on the cationic surface, which is prepared by treating clean fused silica surface with 3-aminopropyltriethoxysilane and subsequently iodomethane. Characteristics of the molecular layer have been examined with contact angle measurement, UV-Vis spectroscopy, grazing-angle FTIR spectroscopy, and NLO property measurement.