Fluorescence emission of disperse red 1 in PS-b-P4VP micelles controlled by a toluene/ethanol solvent mixture

The effects of Disperse Red 1 (DR1) in the poly(styrene-block-4- vinylpyridine) (PS-b-P4VP) micelle on micellar morphology and fluorescence emission were studied using small-angle X-ray scattering (SAXS), generalized indirect Fourier transform (GIFT), Fourier transform infrared (FT-IR), transmission electron microscopy (TEM), and photoluminescence (PL). PS-b-P4VP was coupled with DR1 in 10 mg/mL toluene/ethanol mixture solutions where ethanol and toluene were P4VP and PS selective, respectively. Hydrogen bonds were formed between the-OHgroup of DR1 and the pyridine ring in PS-b-P4VP. DR1 (which was coupled with P4VP) was confined in the core or corona of the micelle depending on the location of P4VP. The micellar structure was strongly dependent on f (weight percentage of toluene in a toluene/ethanol mixture). The PS-b-P4VP-DR1 complex in the mixture solutions showed the spherical micelle with the cores of P4VP and PS in ethanol-rich and toluene-rich solvents, respectively. The quenching phenomenon was observed for DR1 in the corona of PS-b-P4VP micelles [at f = 0 (ethanol)], while the fluorescence quantum yield decreased. However, significant increases in the fluorescence quantum yields at f= 100 were observed when DR1 was confined in the core of the PS-b-P4VP micelles. The confinement of DR1 in the hard core was more effective in fluorescence emission than that in the soft corona due to the slow trans-to-cis transition of DR1.