Liquid–liquid phase separation during amphiphilic self-assembly

Abstract

The self-assembly of amphiphilic molecules in solution is a ubiquitous process in both natural and synthetic systems. The ability to effectively control the structure and properties of these systems is essential for tuning the quality of their functionality, yet the underlying mechanisms governing the transition from molecules to assemblies have not been fully resolved. Here we describe how amphiphilic self-assembly can be preceded by liquid–liquid phase separation. The assembly of a model block co-polymer system into vesicular structures was probed through a combination of liquid-phase electron microscopy, self-consistent field computations and Gibbs free energy calculations. This analysis shows the formation of polymer-rich liquid droplets that act as a precursor in the bottom-up formation of spherical micelles, which then evolve into vesicles. The liquid–liquid phase separation plays a role in determining the resulting vesicles’ structural properties, such as their size and membrane thickness, and the onset of kinetic traps during self-assembly.

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Fig. 1: Phase diagrams for generic amphiphile A–B, showing how the assembly pathway proceeds from a homogenous solution to a liquid–liquid phase-separated state to micellization.
Fig. 2: Formation process of PEO2K-b-PCL10K block copolymer vesicles by LPEM.
Fig. 3: Time-lapsed relative intensity maps show the evolution of the membrane for vesicle 1.
Fig. 4: Overview of the vesicle formation mechanism.
Fig. 5: Quantitative analysis of the LPEM data and comparison with SCF simulations.

Code availability

The matlab script used for image analysis is available from the corresponding author upon reasonable request. The SCF code was provided by F. Leermakers of Wageningen University.

Data availability

All data supporting the findings of this study, including the SCF input files, the data generated by the SCF computations, and the source data for the figures, are available within the Article and its Supplementary Information and/or from the corresponding authors upon reasonable request

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Acknowledgements

J.P.P. was supported by the 4TU High-Tech Materials research program ‘New Horizons in Designer Materials’ and the Marie Sklodowska-Curie Action project ‘LPEMM’. H.W. and M.P.V. are supported by the EU H2020 Marie Sklodowska-Curie Action project ‘MULTIMAT’. The authors thank M. Goudzwaard (Eindhoven University of Technology, the Netherlands) for help with making angular maps and radial-averaged intensity maps.

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Authors

Contributions

J.P.P. and N.A.J.M.S. supervised the study. J.P.P., N.A.J.M.S. and A.I conceived the experiments. H.W., J.P.P. and M.P.V. performed the LPEM experiments. A.C.C.E. and A.I. were responsible for the polymer synthesis and characterization. R.T. and A.I. developed the SCF computations. A.I. developed the theoretical framework. H.F. supervised the movie analysis. A.D.A.K. removed the duplicate frames and stabilized the movies. H.W. developed and conducted the sub-alignments and quantitative analysis. M.M.J.v.R. performed the cryo-TEM experiments. J.P.P. wrote the paper with contributions from all authors. All authors discussed the results and commented on the manuscript.

Corresponding authors

Correspondence to Nico A. J. M. Sommerdijk or Joseph P. Patterson.

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Supplementary information

41557_2019_210_MOESM2_ESM.mov

LPEM Movie of the in-situ self-assembly experiment. Unprocessed movie.

41557_2019_210_MOESM3_ESM.mov

LPEM movie of the in-situ self-assembly experiment. Stabilized and cropped movie. Acquisition frame rate: 30 fps; Electron dose rate: 30 electrons.nm-2.s-1; Playback frame rate: 50 fps.

41557_2019_210_MOESM4_ESM.mov

LPEM movie of the membrane formation process of vesicle 1. Electron dose rate: 30 electrons.nm−2.s−1; Playback frame rate: 100 fps.

41557_2019_210_MOESM5_ESM.mov

Control Experiment 1. LPEM movie of pure acetone. Electron dose rate: 30 electrons.nm−2.s−1; Playback frame rate: 80 fps.

41557_2019_210_MOESM6_ESM.mov

Control Experiment 2. LPEM movie of polymer in acetone. Electron dose rate: 30 electrons.nm−2.s−1; Playback frame rate: 80 fps.

41557_2019_210_MOESM7_ESM.avi

Control Experiment 3. Self-assembly of the vesicles in the liquid cell without imaging.

41557_2019_210_MOESM8_ESM.mov

Control Experiment 4. LPEM movie of preformed vesicle.

41557_2019_210_MOESM9_ESM.mov

Control Experiment 6. LPEM movie showing a second example of the in-situ self-assembly experiment.

41557_2019_210_MOESM10_ESM.mov

Control Experiment 6. LPEM movie showing a cropped single particle from Supplementary Movie 8.

41557_2019_210_MOESM11_ESM.avi

Control Experiment 6. LPEM movie shows a third example of the in-situ self-assembly experiment.

Supplementary Information

Description of the methodologies used, and supplementary in-depth discussions and supplementary data.

Supplementary Movie 1

LPEM Movie of the in-situ self-assembly experiment. Unprocessed movie.

Supplementary Movie 2

LPEM movie of the in-situ self-assembly experiment. Stabilized and cropped movie. Acquisition frame rate: 30 fps; Electron dose rate: 30 electrons.nm-2.s-1; Playback frame rate: 50 fps.

Supplementary Movie 3

LPEM movie of the membrane formation process of vesicle 1. Electron dose rate: 30 electrons.nm−2.s−1; Playback frame rate: 100 fps.

Supplementary Movie 4

Control Experiment 1. LPEM movie of pure acetone. Electron dose rate: 30 electrons.nm−2.s−1; Playback frame rate: 80 fps.

Supplementary Movie 5

Control Experiment 2. LPEM movie of polymer in acetone. Electron dose rate: 30 electrons.nm−2.s−1; Playback frame rate: 80 fps.

Supplementary Movie 6

Control Experiment 3. Self-assembly of the vesicles in the liquid cell without imaging.

Supplementary Movie 7

Control Experiment 4. LPEM movie of preformed vesicle.

Supplementary Movie 8

Control Experiment 6. LPEM movie showing a second example of the in-situ self-assembly experiment.

Supplementary Movie 9

Control Experiment 6. LPEM movie showing a cropped single particle from Supplementary Movie 8.

Supplementary Movie 10

Control Experiment 6. LPEM movie shows a third example of the in-situ self-assembly experiment.

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Ianiro, A., Wu, H., van Rijt, M.M.J. et al. Liquid–liquid phase separation during amphiphilic self-assembly. Nat. Chem. 11, 320–328 (2019). https://doi.org/10.1038/s41557-019-0210-4

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