Nonlinear optical (NLO) materials consisting of organic chromophores have unique optical properties due to the polar molecular structure and noncentrosymmetric ordering of the chromophores. Chromophores with dichlorotriazine moieties can be incorporated with a consistent polar ordering into layer-by-layer films via covalent reaction with a nucleophilic polymeric species. While the manufacture of optical materials traditionally requires highly pure reagents, commercially available azo dyes originally manufactured for textile industry use are usually impure. The purities of three commercially available chromophores, Reactive Red 2, Reactive Orange 4, and Reactive Brown 23, that are being used in NLO materials research were determined by HPLC and found to be highly variable. MALDI-TOF MS analysis of collected HPLC peaks was used to confirm the identity of the chromophores and impurities that resulted from basic hydrolysis. Additionally, since noncentrosymmetric deposition of these chromophores into NLO films occurs at basic pH and hydrolyzed chromophores are not reactive, the stability of the chromophores at pH 10.5 was determined. Base hydrolysis experiments also revealed whether other impurities in the dyes were reactive. Because the layer-by-layer method of making NLO films relies on covalent reaction, the presence of non-reactive impurities may not be a critical issue. However, reactive impurities can take up space and inhibit incorporation of the primary chromophore in the film, and if their dipole moment orientation is different, they may cancel out the molecular ordering of the primary chromophore and further decrease NLO performance.
- Azo dye
- Nonlinear optical
ASJC Scopus subject areas
- Chemical Engineering(all)
- Process Chemistry and Technology