Fluorescence Emission of Disperse Red 1 in PS-b-P4VP Micelles Controlled by a Toluene/Ethanol Solvent Mixture

Abstract

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 -OH group 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 varphi (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 varphi = 0 (ethanol)], while the fluorescence quantum yield decreased. However, significant increases in the fluorescence quantum yields at varphi = 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.