Ma, Qinggao;
Remsen, Edward E.;
Clark, Christopher G.;
Kowalewski, Tomasz;
Wooley, Karen L.
Chemically Induced Supramolecular Reorganization of Triblock Copolymer Assemblies: Trapping of Intermediate States via a Shell-Crosslinking Methodology
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Medientyp:
E-Artikel
Titel:
Chemically Induced Supramolecular Reorganization of Triblock Copolymer Assemblies: Trapping of Intermediate States via a Shell-Crosslinking Methodology
Beteiligte:
Ma, Qinggao;
Remsen, Edward E.;
Clark, Christopher G.;
Kowalewski, Tomasz;
Wooley, Karen L.
Erschienen:
National Academy of Sciences, 2002
Erschienen in:Proceedings of the National Academy of Sciences of the United States of America
Beschreibung:
<p>The mechanism of morphological phase transitions was studied for rod-shaped supramolecular assemblies comprised of a poly(acrylic acid)-block-poly(methyl acrylate)-block-polystyrene (PAA<sub>90</sub>-b-PMA<sub>80</sub>-b-PS<sub>100</sub>) triblock copolymer in 33% tetrahydrofuran/water after perturbation by reaction with a positively charged water-soluble carbodiimide. Tetrahydrofuran solvation of the hydrophobic core domain provided the dynamic nature required for the rod-to-sphere phase transition to be complete within 30 min. The intermediate morphologies such as fragmenting rods and pearl-necklace structures were trapped kinetically by the subsequent addition of a diamino crosslinking agent, which underwent covalent crosslinking of the shell layer. Alternatively, shell-crosslinked rod-shaped nanostructures with preserved morphology were obtained by the addition of the crosslinking agent before the addition of the carbodiimide, which allowed for the shell crosslinking to be performed at a faster rate than the morphological reorganization. The formation of robust shell-crosslinked nanostructures provides a methodology by which the morphological evolution processes can be observed, and it allows access to otherwise thermodynamically unstable nanostructures.</p>