Hierarchical self-assembly from nanometric micelles to colloidal spherical superstructures

Kia Bertula, Nonappa Nonappa, Teemu T.T. Myllymäki, Hongjun Yang, X. X. Zhu, Olli Ikkala

Research output: Contribution to journalArticleScientificpeer-review

5 Citations (Scopus)
92 Downloads (Pure)

Abstract

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.

Original languageEnglish
Pages (from-to)177-187
Number of pages11
JournalPolymer
Volume126
DOIs
Publication statusPublished - 2017
MoE publication typeA1 Journal article-refereed

Keywords

  • Electron tomography
  • Hydrogen bonding
  • Micelles
  • Self-assembly
  • Supermicelles

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  • Projects

    HYBER: The Academy of Finland's Centre of Excellence in Molecular Engineering of Biosynthetic Hybrid Materials research (2014-2019)

    Cherian, T., Nonappa, N., Ikkala, O., Bertula, K., Morits, M., Hynninen, V., Myllymäki, T., Toivonen, M., Sohrabi, F., Haataja, J., Sanchez Sanchez, A., Rissanen, S. & Poutanen, M.

    01/01/201730/06/2020

    Project: Academy of Finland: Other research funding

    ERC Ikkala (ERC)

    Houbenov, N., Nonappa, N., Cherian, T., Haataja, J., Johansson, L., Bertula, K., Martikainen, L., Morits, M., Myllymäki, T., Ikkala, O., Toivonen, M., Sorvari, J. & Sanchez Sanchez, A.

    01/11/201130/09/2017

    Project: EU: ERC grants

    Equipment

    OtaNano

    Anna Rissanen (Manager)

    Aalto University

    Facility/equipment: Facility

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