Cooperativity during Melting and Molecular Exchange in Micelles with Crystalline Cores

Nico König, Lutz Willner, Vitaliy Pipich, Thomas Zinn, and Reidar Lund
Phys. Rev. Lett. 122, 078001 – Published 21 February 2019
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Abstract

Molecular exchange processes are important equilibration and transport mechanisms in both synthetic and biological self-assembled systems such as micelles, vesicles, and membranes. Still, these processes are not entirely understood, in particular the effect of crystallinity and the interplay between cooperative melting processes and chain exchange. Here we focus on a set of simple polymer micelles formed by binary mixtures of poly(ethylene oxide)-mono-n-alkyl-ethers (CnPEO5) which allows the melting point to be tuned over a wide range. We show that the melting transition is cooperative in the confined 4–5 nm micellar core, whereas the exchange process is widely decoupled and unimeric in nature. As confirmed by differential scanning calorimetry, the total activation energy for ejecting a molecule out of the micellar core below the melting point is the sum of the enthalpy of fusion and the corresponding activation energy in the melt state. This suggests that a “local, single-chain melting process” preludes the molecular diffusion out of the micelle during chain exchange.

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  • Received 25 July 2018
  • Revised 19 November 2018

DOI:https://doi.org/10.1103/PhysRevLett.122.078001

© 2019 American Physical Society

Physics Subject Headings (PhySH)

Polymers & Soft Matter

Authors & Affiliations

Nico König1,2,§, Lutz Willner1,*, Vitaliy Pipich3,¶, Thomas Zinn2,†, and Reidar Lund2,‡

  • 1Jülich Centre for Neutron Science (JCNS) and Institute for Complex Systems (ICS), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
  • 2Department of Chemistry, University of Oslo, P.O. Box 1033, Blindern, 0315 Oslo, Norway
  • 3Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Forschungszentrum Jülich GmbH, 85747 Garching, Germany

  • *l.willner@fz-juelich.de ORCID ID:0000-0001-6482-7937
  • Present address: ESRF—The European Synchrotron, 38043 Grenoble Cedex 9, France.
  • reidar.lund@kjemi.uio.no ORCID ID:0000-0001-8017-6396
  • §ORCID ID:0000-0003-3319-5708
  • ORCID ID:0000-0002-3930-3602

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Issue

Vol. 122, Iss. 7 — 22 February 2019

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