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Spherical Micelles with Nonspherical Cores: Effect of Chain Packing on the Micellar Shape
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DOI：10.1021/acs.macromol.0c01936.png)
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Abstract
En 中文
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 C-n-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 epsilon approximate to 0.5) in the crystalline region and abruptly arrange into a more spheroidal shape (e approximate to 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.
Keywords:
BLOCK-COPOLYMER MICELLES
ANGLE X-RAY
SEGMENTAL ORDER PARAMETERS
SOLID-STATE NMR
INTERFACIAL-TENSION
GOLD NANOPARTICLES
POLYMERIC MICELLES
EXCHANGE KINETICS
PHASE-SEPARATION
AQUEOUS-SOLUTION
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