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Spherical Micelles with Nonspherical Cores : Effect of Chain Packing on the Micellar Shape

König, Nico ; Willner, Lutz ; Carlström, Göran LU orcid ; Zinn, Thomas ; Knudsen, Kenneth D. ; Rise, Frode ; Topgaard, Daniel LU and Lund, Reidar (2020) In Macromolecules p.10686-10698
Abstract

Self-assembly of amphiphilic polymers into micelles is an archetypical example of a "self-confined"system due to the formation of micellar cores with dimensions of a few nanometers. In this work, we investigate the chain packing and resulting shape of Cn-PEOx micelles with semicrystalline cores using small/wide-angle X-ray scattering (SAXS/WAXS), contrast-variation small-angle neutron scattering (SANS), and nuclear magnetic resonance spectroscopy (NMR). Interestingly, the n-alkyl chains adopt a rotator-like conformation and pack into prolate ellipses (axial ratio ϵ ≈ 0.5) in the "crystalline"region and abruptly arrange into a more spheroidal shape (ϵ ≈ 0.7) above the melting point. We attribute the distorted spherical shape above the... (More)

Self-assembly of amphiphilic polymers into micelles is an archetypical example of a "self-confined"system due to the formation of micellar cores with dimensions of a few nanometers. In this work, we investigate the chain packing and resulting shape of Cn-PEOx micelles with semicrystalline cores using small/wide-angle X-ray scattering (SAXS/WAXS), contrast-variation small-angle neutron scattering (SANS), and nuclear magnetic resonance spectroscopy (NMR). Interestingly, the n-alkyl chains adopt a rotator-like conformation and pack into prolate ellipses (axial ratio ϵ ≈ 0.5) in the "crystalline"region and abruptly arrange into a more spheroidal shape (ϵ ≈ 0.7) above the melting point. We attribute the distorted spherical shape above the melting point to thermal fluctuations and intrinsic rigidity of the n-alkyl blocks. We also find evidence for a thin dehydrated PEO layer (≤1 nm) close to the micellar core. The results provide substantial insight into the interplay between crystallinity and molecular packing in confinement and the resulting overall micellar shape.

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author
; ; ; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Macromolecules
pages
10686 - 10698
publisher
The American Chemical Society (ACS)
external identifiers
  • scopus:85096590230
  • pmid:33335341
ISSN
0024-9297
DOI
10.1021/acs.macromol.0c01936
language
English
LU publication?
yes
id
3ea798f4-40c9-47f2-813f-d7573c583a13
date added to LUP
2020-12-08 13:57:30
date last changed
2025-03-07 04:18:32
@article{3ea798f4-40c9-47f2-813f-d7573c583a13,
  abstract     = {{<p>Self-assembly of amphiphilic polymers into micelles is an archetypical example of a "self-confined"system due to the formation of micellar cores with dimensions of a few nanometers. In this work, we investigate the chain packing and resulting shape of Cn-PEOx micelles with semicrystalline cores using small/wide-angle X-ray scattering (SAXS/WAXS), contrast-variation small-angle neutron scattering (SANS), and nuclear magnetic resonance spectroscopy (NMR). Interestingly, the n-alkyl chains adopt a rotator-like conformation and pack into prolate ellipses (axial ratio ϵ ≈ 0.5) in the "crystalline"region and abruptly arrange into a more spheroidal shape (ϵ ≈ 0.7) above the melting point. We attribute the distorted spherical shape above the melting point to thermal fluctuations and intrinsic rigidity of the n-alkyl blocks. We also find evidence for a thin dehydrated PEO layer (≤1 nm) close to the micellar core. The results provide substantial insight into the interplay between crystallinity and molecular packing in confinement and the resulting overall micellar shape. </p>}},
  author       = {{König, Nico and Willner, Lutz and Carlström, Göran and Zinn, Thomas and Knudsen, Kenneth D. and Rise, Frode and Topgaard, Daniel and Lund, Reidar}},
  issn         = {{0024-9297}},
  language     = {{eng}},
  pages        = {{10686--10698}},
  publisher    = {{The American Chemical Society (ACS)}},
  series       = {{Macromolecules}},
  title        = {{Spherical Micelles with Nonspherical Cores : Effect of Chain Packing on the Micellar Shape}},
  url          = {{http://dx.doi.org/10.1021/acs.macromol.0c01936}},
  doi          = {{10.1021/acs.macromol.0c01936}},
  year         = {{2020}},
}