Renliang Xu

Study of polystyrene-poly(ethylene oxide) block copolymer micelles in aqueous solution by size-exclusion chromatography

Abstract Size-exclusion chromatography experiments are reported for aqueous solutions of polystyrene-poly-(ethylene oxide) (PS-PEO) diblock and triblock copolymers. These samples show two peaks: the first peak elutes due to polymer micelles (characterized independently by light scattering), and the second due to individual polymer molecules. Sharp micelle peaks imply slow dynamic exchange. By collecting fractions and examining them by Fourier transform infrared spectrometry we were able to establish that the single molecule peak contained more PEO and less PS than the micelle.

Concentration dependence of the transient effects in monomer—excimer kinetics☆☆☆

Abstract Transient effects in pyrene monomer—excimer kinetics were investigated by fluorescence decay studies. The results show that, for methyl 4-(1-pyrenebutyrate), the effective capture radius R′ for the reaction in toluene in smaller than that in cyclohexane and, more surprisingly, the mutual diffusion coefficient Dm in cyclohexane (but not toluene) displays a negative concentration effect.