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The synthesis and characterization of well-defined poly((styrene-alt-diphenylethylene)-bisoprene) diblock copolymers via sequential anionic polymerization are discussed. Indeed, modified 1,1-diphenylethylene commodity elastomers have appeared recently as an alternative to the well-known elastomers for high-temperature applications. The obtained materials were used for the preparation of block copolymer micelles. The hydrodynamic radius of the micelles in solution was determined by dynamic light scattering and the size of the core by atomic force microscopy at dry conditions. It was found that the observed characteristics of the studied micelles correlate to theoretical scaling predictions. Moreover, the average size of the unimers could be determined with high precision from the obtained experimental data and theoretical knowledge.

Micelles prepared from amphiphilic block copolymers in which a poly(styrene) segment is connected to a poly(ethylene oxide) block via a bis-(2,2':6',2"-terpyridine-ruthenium) complex have been intensely studied. In most cases, the micelle populations were found to be strongly heterogeneous in size because of massive micelle/ micelle aggregation. In the study reported in this article we tried to improve the homogeneity of the micelle population. The variant preparation procedure developed, which is described here, was used to prepare two "protomer"-type micelles: PS20-[Ru]PEO70 and PS20-[Ru]-PEO375. The dropwise addition of water to a solution of the compounds in dimethylformamide was replaced by the controlled addition of water by a syringe pump. The resulting micelles were characterized by sedimentation velocity and sedimentation equilibrium analyses in an analytical ultracentrifuge and by transmission electron microscopy of negatively stained samples. Sedimentation analysis showed virtually unimodal size distributions, in contrast to the findings on micelles prepared previously. PS20-[Ru]PEO70 micelles were found to have an average molar mass of 318,000 g/mol (corresponding to 53 protomers per micelle, which is distinctly less than after micelle preparation by the standard method) and an average hydrodynamic diameter (d(h)) of 18 nm. For PS20-[Ru]-PEO375 micelles, the corresponding values were M = 603,000 g/mol (31 protomers per micelle) and dh = 34 nm. The latter particles were found to be identical to the "equilibrium" micelles prepared in pure water. Both micelle types had a very narrow molar mass distribution but a much broader distribution of s values and thus of hydrodynamic diameters. This indicates a conformational heterogeneity that is stable on the time scale of sedimentation velocity analysis. The findings from electron microscopy were in disagreement with those from the sedimentation analysis both in average micelle diameter and in the width of the dis

Metallo-supramolecular diblock copolymers consisting of a polystyrene (PS) block connected to a poly(ethylene oxide) (PEO) block by a bis(terpyridine)ruthenium complex (PS20-[Ru]-PEOy) were used to prepare aqueous micelles. The length of the PS block was kept constant, while two PEOs of different molecular weight were used. The resulting hydrated micelles and aggregates were characterized by a combination of cryogenic transmission electron microscopy (cryo-TEM) and dynamic light scattering measurements. The results were compared to those obtained for a covalent counterpart (PS22-b-PEO70). Cryogenic transmission electron microscopy allowed visualization of the PS core of the micelles. Moreover, the aggregates result from clustering of individual micelles.

The formation of asymmetric bis-complexes, based on terpyridine ligands and ruthenium ions, is described as a powerful tool for the self-assembly of polymer blocks end-functionalized with terpyridine units. This is illustrated in this contribution for the synthesis of amphiphilic metallo-supramolecular block copolymers, which are further used to produce aqueous micelles. Finally, the reversibility of the supramolecular bond opens new avenues for the preparation and manipulation of these nano-objects.

Two different metallo-supramolecular amphiphilic block copolymers have been synthesized, using a hydrophilic poly(ethylene oxide) block connected through a bis-(2,2':6'2"-terpyridine-ruthenium) complex either to a hydrophobic polystyrene or to a poly(ethylene-co-butylene) block. These copolymers were used to prepare aqueous micelles. The morphological characterization of the metallo-supramolecular micelles was performed by dynamic light scattering and transmission electron microscopy. Besides individual micelles, larger structures were also observed by these two independent techniques. The larger structures were the result of aggregation of individual micelles. In addition, the influence of the ionic strength of the medium was investigated. Although the metallo-supramolecular copolymers do not contain charged blocks, the corresponding micelles behaved as polyelectrolyte-like micelles. This behaviour was attributed to the presence of NaCl ions, strongly associated to the poly(ethylene oxide) blocks. This was evidenced by transmission electron microscopy, that revealed the presence of the salt in the metallo-supramolecular micelles. (C) 2003 Society of Chemical Industry.