Self-assembly of non-linear optical chromophores through ionic interactions

Ionic attractions were applied to the construction of non-linear optical (NLO) chromophoric monolayers. In order to fully utilize such an interaction, stilbene-type NLO chromophores having a long alkyl chain and an anionic group at one end of the chain were designed; of this family of chromophores, sodium 11-[4-(trans-4'-pyridylstyry)oxy]undecan-1-yl sulfate (3) was synthesized. By allowing a few minutes, this anionic chromophore self-assembles successfully on a cationically charged surface, which is prepared by treating clean fused silica with 3-aminopropyltriethoxysilane and then with iodomethane. The pyridine moiety of the self-assembled chromophore can be methylated to augment the molecular hyperpolarizability, beta. The characteristics of the monolayer were examined vip contact angle measurements, UV-VIS spectroscopy, grazing-angle FTIR spectroscopy, and NLO property measurements.