Comparison of the characteristic behavior of two azo dyes on temperature dependent microstructure changes in micelles and vesicles.

The new hydrophobic azo dye 4-(N-phenyl-N-decylamino)-4'-nitroazobenzene (AzoC10) has been synthesized. It is compared with 4-(N-phenylamino)-4'-nitroazobenzene (Azo) in terms of reactivity (k(iso) of the thermal cis-->trans isomerization, microsecond flash photolysis) and of the solvatochromic behavior (lambda(max) of the trans-isomer, UV/vis absorption), respectively, within membrane mimeting amphiphile microstructures in aqueous solutions of poly(ethylene oxide)(m)-poly(propylene oxide)(n)-poly(ethylene oxide)(m) micelles and of extruded vesicles. The temperature-induced micelle formation and phase transitions in bilayers of vesicles, respectively, caused characteristic discontinuous changes of k(iso) and lambda(max) with temperature.