Metallo-supramolecular micelles : studies by analytical ultracentrifugation and electron microscopy

In aq. solns., 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 proto-mer type PS20-[Ru]-PEO70, according to the prepn. procedure representing frozen micelles, were studied by sedimentation velocity and sedimentation equil. anal. in an anal. ultracentrifuge and by transmission electron microscopy, with different techniques applied for the sample prepn. The particles obtained were surprisingly multifarious in size. In ultracentrifugation expts. performed at relatively low salt concns., the distributions of the sedimentation coeff. s20,w showed a pronounced peak at 9.6 S and a broad, only partly sepd. second peak around 14 S. The molar mass of the particles at the peak was around 430,000 g/mol, corresponding to an aggregation no. of approx. 85. The av. hydrodynamic diam. of the particles in the peak fraction was approx. 13 nm. In electron micrographs of neg. stained samples, spheres of diams. 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 anal. and electron microscopy showed that (1) the studied compd. formed primary micelles of diams. around 20 nm and (2) the primary micelles had a tendency toward aggregation. [on SciFinder (R)]