title: Chemically induced supramolecular reorganization of triblock copolymer assemblies: trapping of intermediate states via a shell-crosslinking methodology.
abstract: 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(90)-b-PMA(80)-b-PS(100)) 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.
authors.affiliation: Department of Chemistry, Washington University, One Brookings Drive, St. Louis, MO 63130, USA.
authors.forename: Qinggao
authors.initials: Q
authors.lastname: Ma
authors.forename: Edward E
authors.initials: EE
authors.lastname: Remsen
authors.forename: Christopher G
authors.initials: CG
authors.lastname: Clark
authors.forename: Tomasz
authors.initials: T
authors.lastname: Kowalewski
authors.forename: Karen L
authors.initials: KL
authors.lastname: Wooley
mesh_terms: D002234:Carbodiimides / Q000737:chemistry; D003432:Cross-Linking Reagents / Q000494:pharmacology*; D005663:Furans / Q000737:chemistry*; D007700:Kinetics; D008823:Micelles; D008854:Microscopy, Electron; D008956:Models, Chemical; D008958:Models, Molecular; D011108:Polymers / Q000737:chemistry*; D013997:Time Factors; D014867:Water / Q000737:chemistry
chemical_list: D002234:Carbodiimides; D003432:Cross-Linking Reagents; D005663:Furans; D008823:Micelles; D011108:Polymers; D014867:Water; C018674:tetrahydrofuran