Role of the tracer in characterizing the aggregation behavior of aqueous block copolymer solutions using fluorescence correlation spectroscopy |
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Authors: | Tune B Bonné Christine M Papadakis Karin Lüdtke Rainer Jordan |
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Institution: | 1. Physik Department E13, Technische Universit?t München, James-Franck-Str. 1, 85747, Garching, Germany 2. Department Chemie, Lehrstuhl für Makromolekulare Stoffe, Technische Universit?t München, Lichtenbergstr. 4, 85747, Garching, Germany 3. Polymer Research Institute, Polytechnic University, Six Metrotech Center, Brooklyn, NY, 11201, USA
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Abstract: | The hydrodynamic radii of micelles formed by amphiphilic poly(2-alkyl-2-oxazoline) diblock copolymers in aqueous solution
determined using fluorescence correlation spectroscopy (FCS) depend on the nature of the fluorescent tracer used. We have
compared the values of the hydrodynamic radii of the unimers and the micelles as well as the critical micelle concentrations
(CMC), using as tracers (1) the identical diblock copolymers being fluorescence-labeled at the hydrophilic or the hydrophobic
block terminus Bonné et al. Colloid Polym Sci (2004) 282:833–843], and (2) a low molar mass fluorescence dye, rhodamine 6G. Whereas similar values for the CMC were found for
both probes, the hydrodynamic radius of micelles is significantly underestimated using a free dye as a tracer in FCS, especially
near the CMC. We attribute this discrepancy to the fast exchange of the dye between micelles and solution. |
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Keywords: | Polymer physics Amphiphilic block copolymers Aggregation behavior Fluorescence correlation spectroscopy |
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