• Knudsen, Kenneth D.
• Rise, Frode
• Carlström, Göran
• Lund, Reidar
• König, Nico
• Willner, Lutz
• Zinn, Thomas
• Topgaard, Daniel

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>

Topics

• impedance spectroscopy
• polymer
• Nuclear Magnetic Resonance spectroscopy
• crystallinity
• small-angle neutron scattering
• small angle x-ray scattering
• self-assembly
• wide-angle X-ray scattering
• semicrystalline