The evolution of polymolecular micelles formed by two different poly(2-vinylpyridine)-polystyrene (PVP-PS) block copolymers dissolved in toluene is studied by means of transmission electron microscopy (TEM). The two PVP-PS diblock copolymers differ in composition, namely in the length of PVP block. Upon dissolution, a rapid formation of mixed polymolecular micelles takes place. As a result, the micellar size distribution observed is rather broad already at this initial stage. Due to the presence of two different diblock copolymers, the process of micellar growth involves not only the fusion of micelles but also the chain exchange between polymolecular micelles of different composition, which may slow the equilibration process. After a considerable aging time, the block copolymers seem to reach the equilibrium state, and an almost perfect bimodal size distribution is observed. According to the theoretical analysis given, both "pure" and "mixed" micelles constitute the micellar size distribution.

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The equilibration of spherical micelles formed by polystyrene−poly(2-vinylpyridine) (PS−PVP) diblock copolymers in toluene is studied by means of cryo electron microscopy. The evolution of the micelles in order to reach the equilibrium state involves the transformation of their structure and size and requires a considerable time. The micellar size distribution, which is relatively narrow after dissolution, becomes broader with time. The micellar structure changes with time toward a spherical form with narrow interfacial zone between the core and corona regions. The possible scenario of the equilibration process is discussed. The influence of the dilution on the micelles' evolution toward the equilibrium is investigated. It is found that strong dilution can lead to a decrease of the final size of the micelles. The reasons for this phenomenon are discussed.

Solutions of the diblock copolymer polystyrene/poly-2-vinylpyridine (PSP2VP) in toluene were studied by cryo-transmission electron microscopy following fast freezing of a thin film of the solution in liquid nitrogen. The block copolymer forms spherical micelles which can be visualized using phase contrast microscopy. From the measured diameter of copolymer micelles with different block lengths, it can be concluded that only the poly-2-vinylpyridine core is visible in the electron micrographs, whereas the polystyrene corona is not visible and is largely dissolved into the toluene. The block copolymer micelles are rather stable in the beam and provide enough contrast relative to the amorphous toluene, due to the higher density of the micelles relative to the toluene, to be visible without any staining. This opens the possibility to directly visualize the phase behavior of polymer systems in a volatile solvent, perform timeresolved microscopy, and thus study the dynamics of the formation of different morphologies.