Hierarchical self-assembly from nanometric micelles to colloidal spherical superstructures
| Autor: | Olli Ikkala, Kia Bertula, X. X. Zhu, Nonappa, Hongjun Yang, Teemu T. T. Myllymäki |
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| Přispěvatelé: | Department of Applied Physics, University of Montreal, Department of Bioproducts and Biosystems, Aalto-yliopisto, Aalto University |
| Jazyk: | angličtina |
| Rok vydání: | 2017 |
| Předmět: |
Hydrogen bonding
Polymers and Plastics Double bond Allyl glycidyl ether 02 engineering and technology 010402 general chemistry Photochemistry 01 natural sciences Micelle Materials Chemistry Molecule Micelles chemistry.chemical_classification ta114 Chemistry Hydrogen bond Organic Chemistry Polymer Self-assembly 021001 nanoscience & nanotechnology 0104 chemical sciences Solvent Crystallography Electron tomography Supermicelles 0210 nano-technology |
| Popis: | We report sequential self-assembly of low molecular weight asymmetric star-like polymers from nanometric spherical micelles (core diameter 8–12 nm) to colloidal spherical superstructures (d > 500–1000 nm) in aqueous media, as directed by quadruple hydrogen bonding moieties activated by solvent exchanges. The molecules consist of a rigid asymmetric steroidal cholic acid (CA) core, whose hydroxyl groups are first grafted with four oligomeric allyl glycidyl ether (AGE) chains involving six repeat units. The allylic double bonds are thiol-clicked with cysteamine (HS-(CH2)2-NH2), and in the final step their amino end groups are conjugated with 2-ureido-4[1H]-pyrimidinone (UPy) via isocyanate chemistry using UPy-(CH2)6-NCO to obtain asymmetric star-like facially amphiphilic molecules denoted as CA[(AGE-NH2)6]4-(UPy)n. They self-assemble into spherical micelles in dimethyl sulfoxide (DMSO), which suppresses the dimerization of UPys. Solvent exchange from DMSO to water activates the inter-micellar hydrogen bonds via the peripheral UPy units, which triggers the formation of spherical submicron to micron scale superstructures. Based on three-dimensional (3D) reconstruction using transmission electron tomography (ET), we show that such structures are composed of densely packed micellar network. Our work shows that surfactant-like molecules, characteristically leading to micelles, can undergo complex and hierarchical self-assembly to microscale by equipping the solubilising chains with hydrogen bonding units that can be switched ON and OFF by sequential solvent exchanges. |
| Databáze: | OpenAIRE |
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