|290. Walther, A.; Goldmann, A.S.; Yelamanchili, R.S.; Drechsler, M.; Schmalz, H.; Eisenberg, A.; Müller, A.H.E.: Multiple Morphologies, Phase Transitions and Cross-Linking of Crew-Cut Aggregates of Polybutadiene-block-Poly(2-vinylpyridine) Diblock Copolymers, Macromolecules 41, 3254 (2008) -- DOI: 10.1021/ma7026148 -- PDF|
We describe detailed investigations on the self-assembly of polybutadiene-block-poly(2-vinylpyridine) diblock copolymers into so-called crew-cut micellar aggregates in aqueous media. Three diblock copolymers with different short segments of poly(2-vinylpyridine) were synthesized via anionic polymerization. The self-assembled aggregates are studied in dioxane/water mixtures by means of dynamic light scattering and transmission electron microscopy. Depending on the added volume fraction of water, spherical micelles, branched cylindrical micelles and vesicles can be found. These aggregates can be crosslinked in a facile fashion using a UV photoinitiator. The structures of the crew-cut aggregates remain intact during crosslinking, yielding stabilized polymeric nanoparticles. Transfer of these nanoparticles into common, only slightly selective solvents, in which no aggregates or different type of aggregates would exist without crosslinking, is possible. The crosslinked nanoparticle structures remain unchanged during this process. Moreover, a new pathway for the phase transition of cylindrical micelles to vesicles was found and is elucidated.
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