Metallo-Supramolecular Micelles: Studies by Analytical Ultracentrifugation and Electron Microscopy
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Vogel, Vitali; Gohy, Jean-Francois; Lohmeijer, Bas G. G.; van den Broek, Jacomina A.; Haase, Winfried; Schubert, Ulrich S.; Schubert, Dieter
- Abstract:
- In aqueous solutions, amphiphilic block copolymers in which a polystyrene
(PS) segment is connected to a poly(ethylene oxide) (PEO) block via a bis(2,2:6,2-
terpyridine ruthenium) complex can form micelles. Such micelles of the protomer type
PS20-[Ru]-PEO70, according to the preparation procedure representing frozen micelles,
were studied by sedimentation velocity and sedimentation equilibrium analysis in an
analytical ultracentrifuge and by transmission electron microscopy, with different techniques
applied for the sample preparation. The particles obtained were surprisingly multifarious
in size. In ultracentrifugation experiments performed at relatively low salt concentrations,
the distributions of the sedimentation coefficient s20,w showed a pronounced
peak at 9.6 S and a broad, only partly separated second peak around 14 S. The molar mass
of the particles at the peak was around 430,000 g/mol, corresponding to an aggregation
number of approximately 85. The average hydrodynamic diameter of the particles in the
peak fraction was approximately 13 nm. In electron micrographs of negatively stained
samples, spheres of diameters between 10 and 25 nm were the most abundant particles,
but larger ones with a wide size range were also visible. The latter particles apparently
were composed of smaller ones. The data from both sedimentation analysis and electron
microscopy showed that (1) the studied compound formed primary micelles of diameters
around 20 nm and (2) the primary micelles had a tendency toward aggregation.
- Year:
- 2003
- Type of Publication:
- Article
- Keywords:
- metallo supramolecular chemistry; micelles; analytical ultracentrifugation; electron microscopy; block copolymers
- Journal:
- Journal of Polymer Science: Part A: Polymer Chemistry
- Volume:
- 41
- Pages:
- 3159 – 3168