NONLINEAR OPTICAL-PROPERTIES OF POLYMER ION DYE COMPLEXES

One of the composite materials which involve polymers and chromophores, the polymer ion-dye complex, was investigated to establish nonlinear optical properties. The complexes were obtained by an ion exchange reaction between the sulfonic group of the polymers and cationic dyes. Cyanines and triphenylmethanes were used as cationic dyes. The dye content of the complexes could be controlled by means of the polarity of the solution, so that the maximum dye content reached 0.6 at the molar ratio of bound dye to the sulfonic group. The thin films of complexes were made by casting their CHCl3-MeOH solutions on fused quartz plates. All the films obtained were transparent and homogeneous under the polarizing microscope. Nonlinear optical properties of the films were evaluated by third harmonic generation (THG). The third order susceptibility x(3) linearly depends on dye content of the film <M> (mmol/cm3) as well as on pumping wavelengths, and maximum of hemicyanines and crystalviolet well exceeded 10-11nesu. In the complexes of hemicyanines, the dye having longer conjugation gives larger values than the dye having shorter conjugation, at the same <M>. This result agrees with theoretical predictions. © 1990, The Society of Polymer Science, Japan. All rights reserved.