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

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 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 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.

SUBMITTER: Konig N

PROVIDER: S-EPMC7735752 | biostudies-literature | 2020 Dec

REPOSITORIES: biostudies-literature

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

König Nico N Willner Lutz L Carlström Göran G Zinn Thomas T Knudsen Kenneth D KD Rise Frode F Topgaard Daniel D Lund Reidar R

Macromolecules 20201118 23

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, ...[more]

PMID: 33335341

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Project description:In recent years, the development of nanoreactors, such as micellar nanoreactors (MNRs) for catalytic transformations, has gained significant attention due to their potential in enhancing reaction rates, selectivity, efficiency, and, as importantly, the ability to conduct organic chemistry in aqueous solutions. Among these, the copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction represents a pivotal transformation and is widely used in the synthesis of bioconjugates, pharmaceuticals, and advanced materials. This study aims toward advancing our understanding of the design and utilization of polymeric amphiphiles containing tris-triazole ligands as an integral element for CuAAC reactions within MNRs. Specifically, our investigation delves into three critical factors that influence the reaction rate within MNRs: hydrophobicity, architectural configuration of the polymeric ligands, and their concentration. Utilizing the high molecular precision of dendritic amphiphiles, we synthesized polymeric ligands with two distinct architectures, namely, PEG-ditris-triazole amphiphile (DTA) and PEG-monotris-triazole amphiphile (MTA), and explored their CuAAC reactivity through coassembly with commercially available Pluronic P123 amphiphiles. The results indicate that the architecture and the concentration of the polymeric ligands play more dominant roles in influencing the reaction rate than the hydrophobicity of the dendritic blocks. Notably, while MNRs assembled from solely DTA showed a dampened reaction rate, spiking P123 micelles with DTA yielded an MNR with significantly faster rates. Moreover, P123 MNRs spiked with the synthesized MTA demonstrated increased CuAAC reaction rates compared to those spiked with the DTA, and they even outperformed the widely used Tris(benzyltriazolylmethyl)amine ligand. These findings provide valuable insights into the design principles of polymer-based ligands for constructing reactive MNRs and other types of nanoreactors for efficient catalytic transformations.

Dataset Information

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

Publications

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

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