MIXED LANGMUIR AND LANGMUIR-BLODGETT-FILMS OF DISPERSE RED-13 DYE-DERIVATIZED METHACRYLIC HOMOPOLYMER AND CADMIUM STEARATE

Stable mixed monolayers of disperse red-13 dye (DR13)-derivatized meth acrylic homopolymer (HPDR13) and cadmium stearate (CdSt) have been obt ained and transferred as mixed multilayer Langmuir-Blodgett (LB) films . Langmuir monolayers with different mole percentages of HPDR13 were s tudied by surface pressure and surface potential isotherms. In contras t to the poor transferability of pure HPDR13 monolayers, mixed monolay ers could be successfully transferred as Y-type LB films up to a large number of layers. Fourier transform infrared results on the mixed LB films confirmed the transfer of CdSt and HPDR13, while UV-vis spectra indicated a uniform transfer of HPDR13 during multilayer LB deposition and the possible J-aggregation of HPDR13 molecules. X-ray diffraction results were close to those of pure CdSt films, indicating the existe nce of CdSt domains in the mixed LB film. As expected from the presenc e of DR13 chromophores, nonlinear optical effects were observed. Howev er, by using the Z-scan technique for measuring the refractive indices we were able to demonstrate that they were mainly caused by thermal e ffects, with no clear indication of an electronic origin. This calls f or caution when analyzing nonlinear optical effects.