1
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Jeon S, Jun T, Jeon HI, Ahn H, Lee S, Lee B, Ryu DY. Various Low-Symmetry Phases in High-χ and Conformationally Asymmetric PDMS- b-PTFEA Copolymers. Macromolecules 2021. [DOI: 10.1021/acs.macromol.1c01760] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Seungbae Jeon
- Department of Chemical and Biomolecular Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Korea
| | - Taesuk Jun
- Department of Chemical and Biomolecular Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Korea
| | - Hui Il Jeon
- Department of Chemical and Biomolecular Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Korea
| | - Hyungju Ahn
- Industry Technology Convergence Center, Pohang Accelerator Lavatory, 80 Jigok-ro, Nam-gu, Pohang 37673, Korea
| | - Sangwoo Lee
- Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, United States
| | - Byeongdu Lee
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Du Yeol Ryu
- Department of Chemical and Biomolecular Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Korea
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2
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De Mel JU, Gupta S, Willner L, Allgaier J, Stingaciu LR, Bleuel M, Schneider GJ. Manipulating Phospholipid Vesicles at the Nanoscale: A Transformation from Unilamellar to Multilamellar by an n-Alkyl-poly(ethylene oxide). LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:2362-2375. [PMID: 33570419 PMCID: PMC8023706 DOI: 10.1021/acs.langmuir.0c03302] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Revised: 01/27/2021] [Indexed: 05/05/2023]
Abstract
We investigated the influence of an n-alkyl-PEO polymer on the structure and dynamics of phospholipid vesicles. Multilayer formation and about a 9% increase in the size in vesicles were observed by cryogenic transmission electron microscopy (cryo-TEM), dynamic light scattering (DLS), and small-angle neutron/X-ray scattering (SANS/SAXS). The results indicate a change in the lamellar structure of the vesicles by a partial disruption caused by polymer chains, which seems to correlate with about a 30% reduction in bending rigidity per unit bilayer, as revealed by neutron spin echo (NSE) spectroscopy. Also, a strong change in lipid tail relaxation was observed. Our results point to opportunities using synthetic polymers to control the structure and dynamics of membranes, with possible applications in technical materials and also in drug and nutraceutical delivery.
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Affiliation(s)
- Judith U. De Mel
- Department
of Chemistry and Department of Physics & Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Sudipta Gupta
- Department
of Chemistry and Department of Physics & Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Lutz Willner
- Jülich
Center for Neutron Science (JCNS-1) and Institute of Biological Information
Processing (IBI-8) Forschungszentrum Jülich GmbH, 52428 Jülich, Germany
| | - Jürgen Allgaier
- Jülich
Center for Neutron Science (JCNS-1) and Institute of Biological Information
Processing (IBI-8) Forschungszentrum Jülich GmbH, 52428 Jülich, Germany
| | - Laura R. Stingaciu
- Neutron
Sciences Directorate, Oak Ridge National
Laboratory (ORNL), POB 2008, 1 Bethel Valley Road, Oak Ridge, Tennessee 37831, United States
| | - Markus Bleuel
- NIST
Center for Neutron Research, National Institute
of Standards and Technology, Gaithersburg, Maryland 20899-8562, United States
| | - Gerald J. Schneider
- Department
of Chemistry and Department of Physics & Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, United States
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3
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König N, Willner L, Carlström G, Zinn T, Knudsen KD, Rise F, Topgaard D, Lund R. Spherical Micelles with Nonspherical Cores: Effect of Chain Packing on the Micellar Shape. Macromolecules 2020; 53:10686-10698. [PMID: 33335341 PMCID: PMC7735752 DOI: 10.1021/acs.macromol.0c01936] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Revised: 10/23/2020] [Indexed: 11/30/2022]
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.
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Affiliation(s)
- Nico König
- Department
of Chemistry, University of Oslo, P.O. Box 1033, Blindern, 0315 Oslo, Norway
- Jülich
Centre for Neutron Science (JCNS-1) and Institute of Biological Information
Processing (IBI-8), Forschungszentrum Jülich
GmbH, 52425 Jülich, Germany
| | - Lutz Willner
- Jülich
Centre for Neutron Science (JCNS-1) and Institute of Biological Information
Processing (IBI-8), Forschungszentrum Jülich
GmbH, 52425 Jülich, Germany
| | - Göran Carlström
- Centre
for Analysis and Synthesis, Department of Chemistry, Lund University, P.O. Box 124, 22100 Lund, Sweden
| | - Thomas Zinn
- ESRF
- The European Synchrotron, 38043 Grenoble, France
| | - Kenneth D. Knudsen
- Department
for Neutron Materials Characterization, Institute for Energy Technology, P.O. Box 40, 2027 Kjeller, Norway
| | - Frode Rise
- Department
of Chemistry, University of Oslo, P.O. Box 1033, Blindern, 0315 Oslo, Norway
| | - Daniel Topgaard
- Division
of Physical Chemistry, Department of Chemistry, Lund University, Lund, Sweden
| | - Reidar Lund
- Department
of Chemistry, University of Oslo, P.O. Box 1033, Blindern, 0315 Oslo, Norway
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4
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Myhre S, Amann M, Willner L, Knudsen KD, Lund R. How Detergents Dissolve Polymeric Micelles: Kinetic Pathways of Hybrid Micelle Formation in SDS and Block Copolymer Mixtures. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:12887-12899. [PMID: 32960616 PMCID: PMC7660944 DOI: 10.1021/acs.langmuir.0c02123] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/19/2020] [Revised: 09/22/2020] [Indexed: 06/11/2023]
Abstract
Mixtures of amphiphilic polymers and surfactants are used in a wide range of applications, e.g., pharmaceuticals, detergents, cosmetics, and drug delivery systems. Still, many questions remain on how the structure and, in particular, the kinetics of block copolymer micelles are affected in the presence of surfactants and what controls the solubilization kinetics. In this work, we have studied the stability and solubilization kinetics of block copolymer micelles upon the addition of the surfactant sodium dodecyl sulfate (SDS) using small-angle X-ray/neutron scattering. The ability of the surfactant to dissolve polymer micelles or form mixed micelles has been investigated using two types of amphiphilic polymers, poly(ethylene-alt-propylene)-poly(ethylene oxide) (PEP1-PEO20) and n-alkyl-functionalized PEO (C28-PEO5). The exchange kinetics of C28-PEO5 micelles are in the order of hours, while PEP1-PEO20 micelles are known to be frozen on a practical timescale. In this work, we show that the addition of SDS to PEP1-PEO20 provides virtually no solubilization, even after an extended period of time. However, upon adding SDS to C28-PEO5 micelles, we observe micellar dissolution and formation of mixed micelles occurring on the timescale of hours. Using a coexistence model of mixed and neat micelles, the SAXS data were analyzed to provide detailed structural parameters over time. First, we observe a fast fragmentation/fission step followed by a slow reorganization process. The latter process is essentially independent of concentration at low volume fraction but is greatly accelerated at larger concentrations. This might indicate a crossover from a predominance of molecular exchange to fusion/fission processes.
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Affiliation(s)
- Synne Myhre
- Department
of Chemistry, University of Oslo, Oslo 0315, Norway
| | - Matthias Amann
- Department
of Chemistry, University of Oslo, Oslo 0315, Norway
| | - Lutz Willner
- Jülich
Centre for Neutron Science (JCNS-1) and Institute of Biological Information
Processing (IBI-8) Forschungszentrum Jülich GmbH, Jülich 52425, Germany
| | - Kenneth D. Knudsen
- IFE, Institute
for Energy Technology, Instituttveien 18, Kjeller 2007, Norway
| | - Reidar Lund
- Department
of Chemistry, University of Oslo, Oslo 0315, Norway
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5
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Chang AB, Bates FS. Impact of Architectural Asymmetry on Frank-Kasper Phase Formation in Block Polymer Melts. ACS NANO 2020; 14:11463-11472. [PMID: 32820895 DOI: 10.1021/acsnano.0c03846] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
In recent decades, the discoveries of complex low-symmetry phases in soft matter have inspired advances in molecular and materials design. However, understanding the mechanisms underlying symmetry selection across soft matter remains an important challenge in materials science. Block polymers represent attractive model materials because they permit wide synthetic tunability and provide access to multiple length scales (1-100 nm). However, to date the block polymer design space has been largely limited to variations in molecular weight, block volume fraction, and conformational asymmetry. The molecular architecture-the way in which chains are connected-offers rich potential but remains relatively unexplored in experimental block polymers. Our work bridges this gap, connecting molecular architecture, space-filling demands, and symmetry selection in block polymer self-assembly. Three series of block polymers were synthesized by living polymerization, tuning the architectural asymmetry across the linear-b-linear and linear-b-bottlebrush limits. The bottlebrush architecture amplifies two key ingredients for the formation of Frank-Kasper phases: high conformational asymmetry and high self-concentration. Analysis by small-angle X-ray scattering provides insight into the impact of architectural asymmetry on block polymer self-assembly. Increasing the asymmetry between blocks opens the complex phase window, expanding opportunities to tune symmetry selection in block polymer melts.
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Affiliation(s)
- Alice B Chang
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Frank S Bates
- Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, United States
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6
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González García Á, Ianiro A, Beljon R, Leermakers FAM, Tuinier R. (Homo)polymer-mediated colloidal stability of micellar solutions. SOFT MATTER 2020; 16:1560-1571. [PMID: 31950966 DOI: 10.1039/c9sm01665a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Despite their wide range of applications, there is a remarkable lack of fundamental understanding about how micelles respond to other components in solution. The colloidal stability of micellar solutions in presence of (homo)polymers is investigated here following a theoretical bottom-up approach. A polymer-mediated micelle-micelle interaction is extracted from changes in the micelle-unimer equilibrium as a function of the inter-micelle distance. The homopolymer-mediated diblock copolymer micelle-micelle interaction is studied both for depletion and adsorption of the homopolymer. The fluffy nature of the solvophilic domain (corona) of the micelle weakens the depletion-induced destabilization. Accumulation of polymers into the corona induces bridging attraction between micelles. In fact, both depletion and adsorption phenomena are regulated by the coronal thickness relative to the size of the added polymer. Penetration of guest compounds into the coronal domain of crew-cut micelles, with a narrower yet denser corona, is less pronounced as for starlike micelles (with a more diffuse corona). Therefore, crew-cut micelles are less sensitive to the effect of added compounds, and hence more suitable for applications in multicomponent systems, such as industrial formulations or biological fluids. The trends observed for the colloidal stability of crew-cut micelles qualitatively match with our experimental observations on aqueous dispersions of polycaprolactone-polyethylene glycol (PCL-PEO) micellar suspensions with added PEO chains.
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Affiliation(s)
- Álvaro González García
- Van't Hoff Laboratory for Physical and Colloid Chemistry, Department of Chemistry & Debye Institute, Utrecht University, Padualaan 8, 3584 CH, The Netherlands.
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7
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Jung FA, Panteli PA, Ko CH, Kang JJ, Barnsley LC, Tsitsilianis C, Patrickios CS, Papadakis CM. Structural Properties of Micelles Formed by Telechelic Pentablock Quaterpolymers with pH-Responsive Midblocks and Thermoresponsive End Blocks in Aqueous Solution. Macromolecules 2019. [DOI: 10.1021/acs.macromol.9b01775] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Florian A. Jung
- Fachgebiet Physik weicher Materie, Physik-Department, Technische Universität München, James-Franck Str. 1, 85748 Garching, Germany
| | - Panayiota A. Panteli
- Department of Chemistry, University of Cyprus, P. O. Box 20537, 1678 Nicosia, Cyprus
| | - Chia-Hsin Ko
- Fachgebiet Physik weicher Materie, Physik-Department, Technische Universität München, James-Franck Str. 1, 85748 Garching, Germany
| | - Jia-Jhen Kang
- Fachgebiet Physik weicher Materie, Physik-Department, Technische Universität München, James-Franck Str. 1, 85748 Garching, Germany
| | - Lester C. Barnsley
- Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Forschungszentrum Jülich GmbH, Lichtenbergstr. 1, 85748 Garching, Germany
| | | | - Costas S. Patrickios
- Department of Chemistry, University of Cyprus, P. O. Box 20537, 1678 Nicosia, Cyprus
| | - Christine M. Papadakis
- Fachgebiet Physik weicher Materie, Physik-Department, Technische Universität München, James-Franck Str. 1, 85748 Garching, Germany
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8
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König N, Willner L, Lund R. Structure and thermodynamics of mixed polymeric micelles with crystalline cores: tuning properties via co-assembly. SOFT MATTER 2019; 15:7777-7786. [PMID: 31482169 DOI: 10.1039/c9sm01452g] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We investigate micelles formed by mixtures of n-alkyl-poly(ethylene oxide) block copolymers, Cn-PEO, with different alkyl block lengths in aqueous solution. This model system has previously been used to shed light on the interplay between exchange kinetics and crystallinity in self-assembling systems [König et al., Phys. Rev. Lett., 2019, 122, 078001]. Now we report on the structure and thermodynamics of these micelles by combining results from small-angle X-ray scattering, differential scanning calorimetry and volumetric measurements. We show that mixed micelles are formed despite the fact that length-mismatched n-alkanes of similar weights in bulk tend to demix below the crystallization temperature. Instead, the system exhibits similar properties as single-component micelles but with a modulated melting region. Interestingly, the melting point depression due to self-confinement within the micellar core can be approximately described by a generalized Gibbs-Thomson equation, similar to single-component micelles [Zinn et al. Phys. Rev. Lett., 2014, 113, 238305]. Furthermore, we find a novel scaling law for these micelles where, at least for larger n, the aggregation number scales with the third power of the length of the hydrophobic block, Nagg ∝ n3. Possibly, there might be a cross-over from the conventional Nagg ∝ n2 behaviour around n ≈ 19. However, the reason for such a transition as well as the strong n dependence remains a challenge and requires more theoretical work.
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Affiliation(s)
- Nico König
- Department of Chemistry, University of Oslo, Postboks 1033 Blindern, 0315 Oslo, Norway.
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9
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Dahal UR, Prhashanna A, Dormidontova EE. Hydration of diblock copolymer micelles: Effects of hydrophobicity and co-solvent. J Chem Phys 2019; 150:184908. [PMID: 31091932 DOI: 10.1063/1.5089251] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Diblock polymer micelles dispersed in an aqueous environment are being actively investigated for various applications, but there is only a qualitative understanding of the effect of the chemical structure on the micelle hydration and water dynamics as these properties are difficult to assess experimentally. Using all-atom molecular dynamics simulations, we investigate aqueous solutions of three comparable in size diblock copolymer micelles with core-forming blocks of different hydrophobicity: polybutadiene (PB), polycaprolactone (PCL), and polytetrahydrofuran (pTHF) with the same hydrophilic block, polyethylene oxide (PEO). We found that core-block hydrophobicity and ability to form hydrogen bonds with water strongly affect the water dynamics near the core: water molecules spend considerably less time in contact with the PB block than with PCL and pTHF blocks. We obtained polymer and solvent volume fraction profiles and determined that the interfacial width systematically increases with a decrease of core block hydrophobicity with water penetration into the core being negligible for PB-PEO and PCL-PEO micelles, while for pTHF-PEO micelles the interface is more diffuse and there is a noticeable penetration of water (17% by volume). For PCL-PEO micelles, which are commonly used in biomedical applications, we also investigated tetrahydrofuran (THF) penetration into the micelles from mixed THF:water solution at early stages of micelle dissolution. We found an inhomogeneous solvent distribution with a maximum of THF volume fraction in the interfacial core-corona region and partial exclusion from the PEO corona, which slows down micelle dissolution. These results can have important implications for micelle stability and use in biomedical applications.
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Affiliation(s)
- Udaya R Dahal
- Polymer Program, Institute of Materials Science and Physics Department, University of Connecticut, Storrs, Connecticut 06269, USA
| | - Ammu Prhashanna
- Polymer Program, Institute of Materials Science and Physics Department, University of Connecticut, Storrs, Connecticut 06269, USA
| | - Elena E Dormidontova
- Polymer Program, Institute of Materials Science and Physics Department, University of Connecticut, Storrs, Connecticut 06269, USA
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10
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König N, Willner L, Pipich V, Zinn T, Lund R. Cooperativity during Melting and Molecular Exchange in Micelles with Crystalline Cores. PHYSICAL REVIEW LETTERS 2019; 122:078001. [PMID: 30848643 DOI: 10.1103/physrevlett.122.078001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Revised: 11/19/2018] [Indexed: 06/09/2023]
Abstract
Molecular exchange processes are important equilibration and transport mechanisms in both synthetic and biological self-assembled systems such as micelles, vesicles, and membranes. Still, these processes are not entirely understood, in particular the effect of crystallinity and the interplay between cooperative melting processes and chain exchange. Here we focus on a set of simple polymer micelles formed by binary mixtures of poly(ethylene oxide)-mono-n-alkyl-ethers (C_{n}-PEO5) which allows the melting point to be tuned over a wide range. We show that the melting transition is cooperative in the confined 4-5 nm micellar core, whereas the exchange process is widely decoupled and unimeric in nature. As confirmed by differential scanning calorimetry, the total activation energy for ejecting a molecule out of the micellar core below the melting point is the sum of the enthalpy of fusion and the corresponding activation energy in the melt state. This suggests that a "local, single-chain melting process" preludes the molecular diffusion out of the micelle during chain exchange.
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Affiliation(s)
- Nico König
- Jülich Centre for Neutron Science (JCNS) and Institute for Complex Systems (ICS), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
- Department of Chemistry, University of Oslo, P.O. Box 1033, Blindern, 0315 Oslo, Norway
| | - Lutz Willner
- Jülich Centre for Neutron Science (JCNS) and Institute for Complex Systems (ICS), Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
| | - Vitaliy Pipich
- Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Forschungszentrum Jülich GmbH, 85747 Garching, Germany
| | - Thomas Zinn
- Department of Chemistry, University of Oslo, P.O. Box 1033, Blindern, 0315 Oslo, Norway
| | - Reidar Lund
- Department of Chemistry, University of Oslo, P.O. Box 1033, Blindern, 0315 Oslo, Norway
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11
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Babič A, Vorobiev V, Trefalt G, Crowe LA, Helm L, Vallée JP, Allémann E. MRI micelles self-assembled from synthetic gadolinium-based nano building blocks. Chem Commun (Camb) 2019; 55:945-948. [DOI: 10.1039/c8cc08875f] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Synthetic self-assembled stealth Gd-micelles are a new blood pool contrast agent for magnetic resonance imaging.
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Affiliation(s)
- Andrej Babič
- Pharmaceutical Technology, School of Pharmaceutical Sciences, University of Geneva, University of Lausanne
- 1211 Geneva 4
- Switzerland
| | - Vassily Vorobiev
- Pharmaceutical Technology, School of Pharmaceutical Sciences, University of Geneva, University of Lausanne
- 1211 Geneva 4
- Switzerland
| | - Gregor Trefalt
- Department of Inorganic and Analytical Chemistry, University of Geneva
- 1205 Geneva 4
- Switzerland
| | - Lindsey A. Crowe
- Department of Radiology and Medical Informatics, Faculty of Medicine, University of Geneva
- 1211 Geneva 4
- Switzerland
| | - Lothar Helm
- Institut des Sciences et Ingénierie Chimiques, École Polytechnique Fédérale de Lausanne
- 1015 Lausanne
- Switzerland
| | - Jean-Paul Vallée
- Department of Radiology and Medical Informatics, Faculty of Medicine, University of Geneva
- 1211 Geneva 4
- Switzerland
| | - Eric Allémann
- Pharmaceutical Technology, School of Pharmaceutical Sciences, University of Geneva, University of Lausanne
- 1211 Geneva 4
- Switzerland
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12
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García Á, Ianiro A, Tuinier R. On the Colloidal Stability of Spherical Copolymeric Micelles. ACS OMEGA 2018; 3:17976-17985. [PMID: 30613816 PMCID: PMC6312634 DOI: 10.1021/acsomega.8b02548] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Accepted: 12/07/2018] [Indexed: 06/09/2023]
Abstract
Using self-consistent field (SCF) calculations, we systematically quantify the pair interactions between spherical diblock copolymer micelles following a bottom-up approach. From the equilibrium properties of self-assembling micelles at different separation distances, a simple yet insightful pair interaction can be extracted. The SCF results match with an analytical model based upon closed expressions for the free energy change per diblock copolymer in the micelle. To gain insights into the colloidal stability of dilute micelle suspensions, the second virial coefficient normalized by the undistorted micelle volume (B 2 *) is evaluated. For stable micelles (B 2 * ≳ -6), we find a weak dependence of B 2 * on solvophilic block length for varying core-forming block properties (core solvation and block length). The micelle suspension gets unstable (B 2 * ≲ -6) when the corona-forming block crosses Θ-solvent conditions toward poor solvency. In contrast with what is expected from models where the soft nature of the micelle is not taken into account, increasing the effective grafting density of solvophilic tails from the core then leads to colloidal destabilization of the micelle suspension.
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Affiliation(s)
- Álvaro
González García
- Van
’t Hoff Laboratory for Physical and Colloid Chemistry, Department
of Chemistry & Debye Institute, Utrecht
University, Padualaan
8, 3584 CH Utrecht, The Netherlands
- Laboratory
of Physical Chemistry, Department of Chemical Engineering and Chemistry,
& Institute for Complex Molecular Systems (ICMS), Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
| | - Alessandro Ianiro
- Laboratory
of Physical Chemistry, Department of Chemical Engineering and Chemistry,
& Institute for Complex Molecular Systems (ICMS), Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
| | - Remco Tuinier
- Van
’t Hoff Laboratory for Physical and Colloid Chemistry, Department
of Chemistry & Debye Institute, Utrecht
University, Padualaan
8, 3584 CH Utrecht, The Netherlands
- Laboratory
of Physical Chemistry, Department of Chemical Engineering and Chemistry,
& Institute for Complex Molecular Systems (ICMS), Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
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13
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Structure and solvation thermodynamics of asymmetric poly (acrylic acid)-b-polystyrene polyelectrolyte block copolymer micelle in water: Effect of charge density and chemical composition. POLYMER 2018. [DOI: 10.1016/j.polymer.2018.10.042] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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14
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Vuorte M, Määttä J, Sammalkorpi M. Simulations Study of Single-Component and Mixed n-Alkyl-PEG Micelles. J Phys Chem B 2018; 122:4851-4860. [PMID: 29664641 PMCID: PMC6150674 DOI: 10.1021/acs.jpcb.8b00398] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Revised: 03/26/2018] [Indexed: 11/29/2022]
Abstract
Here, we study one-component and mixed n-alkyl-poly(ethylene glycol) (C mE n) micelles with varying poly(ethylene glycol) (PEG) chain lengths n using coarse-grained molecular simulations. These nonionic alkyl-PEG surfactants and their aggregates are widely used in bio and chemical technology. As expected, the simulations show that increasing the PEG chain length decreases the alkyl-PEG micelle core diameter and the aggregation number but also enhances PEG chain penetration to the core region and spreads the micelle corona. Both the core and corona density are heavily dependent on the PEG chain length and decrease with increasing PEG length. Furthermore, we find that the alkyl-PEG surfactants exhibit two distinct micellization modes: surfactants with short PEG chains as their hydrophilic heads aggregate with the PEG heads relatively extended. Their aggregation number and the PEG corona density are dictated by the core carbon density. For longer PEG chains, the PEG sterics, that is, the volume occupied by the PEG head group, becomes the critical factor limiting the aggregation. Finally, simulations of binary mixtures of alkyl-PEGs of two different PEG chain lengths show that even in the absence of core-freezing, the surfactants prefer the aggregate size of their single-component solutions with the segregation propelled via enthalpic contributions. The findings, especially as they provide a handle on the density and the density profile of the aggregates, raise attention to effective packing shape as a design factor of micellar systems, for example, drug transport, solubilization, or partitioning.
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Affiliation(s)
- Maisa Vuorte
- Department of Chemistry and Materials
Science, School of Chemical Engineering, Aalto University, P.O. Box 16100, FI-00076 Aalto, Finland
| | - Jukka Määttä
- Department of Chemistry and Materials
Science, School of Chemical Engineering, Aalto University, P.O. Box 16100, FI-00076 Aalto, Finland
| | - Maria Sammalkorpi
- Department of Chemistry and Materials
Science, School of Chemical Engineering, Aalto University, P.O. Box 16100, FI-00076 Aalto, Finland
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15
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Onuma T, Yoshio M, Obi M, Kashiwagi K, Tahara S, Kato T. Liquid-crystalline behavior and ion transport properties of block-structured molecules containing a perfluorinated ethylene oxide moiety complexed with a lithium salt. Polym J 2018. [DOI: 10.1038/s41428-018-0051-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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16
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Dai J, Alaei Z, Plazzotta B, Pedersen JS, Furó I. Release of Solubilizate from Micelle upon Core Freezing. J Phys Chem B 2017; 121:10353-10363. [PMID: 29050474 DOI: 10.1021/acs.jpcb.7b08912] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
By combining NMR (yielding 1H chemical shift, spin relaxation, and self-diffusion data) and small-angle X-ray scattering experiments, we investigate the complex temperature dependence of the molecular and aggregate states in aqueous solutions of the surfactant [CH3(CH2)17(OCH2CH2)20OH], abbreviated as C18E20, and hexamethyldisiloxane, HMDSO. The latter molecule serves as a model for hydrophobic solubilizates. Previously, the pure micellar solution was demonstrated to exhibit core freezing at approximately 7-8 °C. At room temperature, we find that HMDSO solubilizes at a volume fraction of approximately 10% in the core of the C18E20 micelles, which consists of molten and thereby highly mobile alkyl chains. Upon lowering the temperature, core freezing is found, just like in pure micelles, but at a temperature shifted significantly to 3 °C. The frozen cores contain immobile alkyl chains and exhibit a higher density but are essentially devoid (volume fraction below 1%) of the solubilizate. The latter molecules are released, first gradually and then rather steeply, from the core in the temperature range that is roughly delimited by the two core freezing temperatures, one for pure micelles and one for micelles with solubilizates. The release behavior of systems with different initial HMDSO loading follows the same master curve. This feature is rationalized in terms of loading capacity being strongly temperature dependent: upon lowering the temperature, release commences once the loading capacity descends below the actual solubilizate content. The sharp release curves and the actual release mechanism with its molecular features shown in rich detail have some bearing on a diverse class of possible applications.
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Affiliation(s)
- Jing Dai
- Division of Applied Physical Chemistry, Department of Chemistry, KTH Royal Institute of Technology , SE-10044 Stockholm, Sweden
| | - Zahra Alaei
- Division of Applied Physical Chemistry, Department of Chemistry, KTH Royal Institute of Technology , SE-10044 Stockholm, Sweden
| | - Beatrice Plazzotta
- Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, Aarhus University , Gustav Wieds Vej 14, 8000 Aarhus C, Denmark
| | - Jan Skov Pedersen
- Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, Aarhus University , Gustav Wieds Vej 14, 8000 Aarhus C, Denmark
| | - István Furó
- Division of Applied Physical Chemistry, Department of Chemistry, KTH Royal Institute of Technology , SE-10044 Stockholm, Sweden
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17
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Zinn T, Willner L, Knudsen KD, Lund R. Self-Assembly of Mixtures of Telechelic and Monofunctional Amphiphilic Polymers in Water: From Clusters to Flowerlike Micelles. Macromolecules 2017. [DOI: 10.1021/acs.macromol.7b01501] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- Thomas Zinn
- Department
of Chemistry, University of Oslo, Postboks 1033 Blindern, 0315 Oslo, Norway
| | - Lutz Willner
- Jülich
Centre for Neutron Science JCNS and Institute for Complex Systems
ICS, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
| | - Kenneth D. Knudsen
- Department
of Physics, Institute for Energy Technology, Postboks 40, 2027 Kjeller, Norway
| | - Reidar Lund
- Department
of Chemistry, University of Oslo, Postboks 1033 Blindern, 0315 Oslo, Norway
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18
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SANS study on self-assembled structures of glucose-responsive phenylboronate ester-containing diblock copolymer. Eur Polym J 2016. [DOI: 10.1016/j.eurpolymj.2016.08.019] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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19
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Akpinar B, Fielding LA, Cunningham VJ, Ning Y, Mykhaylyk OO, Fowler PW, Armes SP. Determining the Effective Density and Stabilizer Layer Thickness of Sterically Stabilized Nanoparticles. Macromolecules 2016; 49:5160-5171. [PMID: 27478250 PMCID: PMC4963924 DOI: 10.1021/acs.macromol.6b00987] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Revised: 06/27/2016] [Indexed: 01/27/2023]
Abstract
A series of model sterically stabilized diblock copolymer nanoparticles has been designed to aid the development of analytical protocols in order to determine two key parameters: the effective particle density and the steric stabilizer layer thickness. The former parameter is essential for high resolution particle size analysis based on analytical (ultra)centrifugation techniques (e.g., disk centrifuge photosedimentometry, DCP), whereas the latter parameter is of fundamental importance in determining the effectiveness of steric stabilization as a colloid stability mechanism. The diblock copolymer nanoparticles were prepared via polymerization-induced self-assembly (PISA) using RAFT aqueous emulsion polymerization: this approach affords relatively narrow particle size distributions and enables the mean particle diameter and the stabilizer layer thickness to be adjusted independently via systematic variation of the mean degree of polymerization of the hydrophobic and hydrophilic blocks, respectively. The hydrophobic core-forming block was poly(2,2,2-trifluoroethyl methacrylate) [PTFEMA], which was selected for its relatively high density. The hydrophilic stabilizer block was poly(glycerol monomethacrylate) [PGMA], which is a well-known non-ionic polymer that remains water-soluble over a wide range of temperatures. Four series of PGMA x -PTFEMA y nanoparticles were prepared (x = 28, 43, 63, and 98, y = 100-1400) and characterized via transmission electron microscopy (TEM), dynamic light scattering (DLS), and small-angle X-ray scattering (SAXS). It was found that the degree of polymerization of both the PGMA stabilizer and core-forming PTFEMA had a strong influence on the mean particle diameter, which ranged from 20 to 250 nm. Furthermore, SAXS was used to determine radii of gyration of 1.46 to 2.69 nm for the solvated PGMA stabilizer blocks. Thus, the mean effective density of these sterically stabilized particles was calculated and determined to lie between 1.19 g cm-3 for the smaller particles and 1.41 g cm-3 for the larger particles; these values are significantly lower than the solid-state density of PTFEMA (1.47 g cm-3). Since analytical centrifugation requires the density difference between the particles and the aqueous phase, determining the effective particle density is clearly vital for obtaining reliable particle size distributions. Furthermore, selected DCP data were recalculated by taking into account the inherent density distribution superimposed on the particle size distribution. Consequently, the true particle size distributions were found to be somewhat narrower than those calculated using an erroneous single density value, with smaller particles being particularly sensitive to this artifact.
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Affiliation(s)
- Bernice Akpinar
- Department
of Chemistry, University of Sheffield, Brook Hill, Sheffield, South Yorkshire S3 7HF, U.K.
| | - Lee A. Fielding
- Department
of Chemistry, University of Sheffield, Brook Hill, Sheffield, South Yorkshire S3 7HF, U.K.
- School
of Materials, The University of Manchester, Oxford Road, Manchester, M13 9PL, U.K.
| | - Victoria J. Cunningham
- Department
of Chemistry, University of Sheffield, Brook Hill, Sheffield, South Yorkshire S3 7HF, U.K.
| | - Yin Ning
- Department
of Chemistry, University of Sheffield, Brook Hill, Sheffield, South Yorkshire S3 7HF, U.K.
| | - Oleksandr O. Mykhaylyk
- Department
of Chemistry, University of Sheffield, Brook Hill, Sheffield, South Yorkshire S3 7HF, U.K.
| | - Patrick W. Fowler
- Department
of Chemistry, University of Sheffield, Brook Hill, Sheffield, South Yorkshire S3 7HF, U.K.
| | - Steven P. Armes
- Department
of Chemistry, University of Sheffield, Brook Hill, Sheffield, South Yorkshire S3 7HF, U.K.
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20
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Zinn T, Willner L, Pipich V, Richter D, Lund R. Molecular Exchange Kinetics of Micelles: Corona Chain Length Dependence. ACS Macro Lett 2016; 5:884-888. [PMID: 35614762 DOI: 10.1021/acsmacrolett.6b00395] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The rate of molecular exchange in diblock copolymer micelles is strongly dependent on the chain length of the core-forming insoluble block. Less is known about the influence of the soluble block forming the micellar corona. In this study we present a time-resolved small angle neutron scattering (TR-SANS) study exploring systematically the effect of corona chain length on the dynamics of chain exchange. As a model system we have taken amphiphilic AB diblock copolymers of the type C27H55-poly(ethylene oxide)x (C27-PEOx) with varying x between 4 and 36 kg/mol in aqueous solution in which well-defined spherical micelles with partially crystalline cores are formed. The TR-SANS results show that the chain exchange slows down considerably upon increasing PEO molecular weight, while the characteristic "attempt time" constant, τ0, was found to increase with a power law dependence τ0 ∼ MPEO9/5. The results are in excellent agreement with the Halperin and Alexander model1 and can be attributed to a reduced diffusion rate through the micellar corona. Our results clearly demonstrate that the rate for molecular exchange is not directly coupled to the solubility of the amphiphile and the critical micellar concentration, as has previously been indicated.
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Affiliation(s)
- Thomas Zinn
- Department
of Chemistry, University of Oslo, Postboks 1033 Blindern, 0315 Oslo, Norway
| | - Lutz Willner
- Jülich
Centre for Neutron Science JCNS and Institute for Complex Systems
ICS, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
| | - Vitaliy Pipich
- Jülich
Centre for Neutron Science JCNS, Forschungszentrum Jülich GmbH, Outstation
at MLZ, Lichtenbergstrasse 1 85747 Garching, Germany
| | - Dieter Richter
- Jülich
Centre for Neutron Science JCNS and Institute for Complex Systems
ICS, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
| | - Reidar Lund
- Department
of Chemistry, University of Oslo, Postboks 1033 Blindern, 0315 Oslo, Norway
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21
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Ma Y, Lodge TP. Poly(methyl methacrylate)-block-poly(n-butyl methacrylate) Diblock Copolymer Micelles in an Ionic Liquid: Scaling of Core and Corona Size with Core Block Length. Macromolecules 2016. [DOI: 10.1021/acs.macromol.6b00315] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- Yuanchi Ma
- Department of Chemistry and ‡Department of Chemical Engineering
and Materials
Science, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Timothy P. Lodge
- Department of Chemistry and ‡Department of Chemical Engineering
and Materials
Science, University of Minnesota, Minneapolis, Minnesota 55455, United States
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22
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Radulescu A, Székely NK, Polachowski S, Leyendecker M, Amann M, Buitenhuis J, Drochner M, Engels R, Hanslik R, Kemmerling G, Lindner P, Papagiannopoulos A, Pipich V, Willner L, Frielinghaus H, Richter D. Tuning the instrument resolution using chopper and time of flight at the small-angle neutron scattering diffractometer KWS-2. J Appl Crystallogr 2015; 48:1849-1859. [PMID: 26664343 PMCID: PMC4665661 DOI: 10.1107/s1600576715019019] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2015] [Accepted: 10/09/2015] [Indexed: 11/24/2022] Open
Abstract
Using a double-disc chopper with a variable slit opening in concert with a velocity selector and the time-of-flight data acquisition mode, controlled variation of the wavelength spread Δλ/λ between 2 and 20% has become routinely possible at the KWS-2 SANS diffractometer of the Jülich Centre for Neutron Science at the Heinz Maier-Leibnitz Center. Following demand from the user community regarding the possibility of improving the experimental resolution, the dedicated high-intensity/extended Q-range SANS diffractometer KWS-2 of the Jülich Centre for Neutron Science at the Heinz Maier-Leibnitz Center in Garching was equipped with a double-disc chopper with a variable opening slit window and time-of-flight (TOF) data acquisition option. The chopper used in concert with a dedicated high-intensity velocity selector enables the tuning at will of the wavelength resolution Δλ/λ within a broad range, from 20% (standard) down to 2%, in a convenient and safe manner following pre-planned or spontaneous decisions during the experiment. The new working mode is described in detail, and its efficiency is demonstrated on several standard samples with known properties and on a completely new crystallizable copolymer system, which were investigated using both the conventional (static) and TOF modes.
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Affiliation(s)
- Aurel Radulescu
- Jülich Centre for Neutron Science (JCNS), Outstation at MLZ, Forschungszentrum Jülich GmbH, Lichtenbergstrasse 1, Garching, 85747, Germany
| | - Noémi Kinga Székely
- Jülich Centre for Neutron Science (JCNS), Outstation at MLZ, Forschungszentrum Jülich GmbH, Lichtenbergstrasse 1, Garching, 85747, Germany
| | - Stephan Polachowski
- Zentralinstitut für Engineering, Elektronik und Analytik (ZEA), Forschungszentrum Jülich GmbH, Jülich, 52425, Germany
| | - Marko Leyendecker
- Zentralinstitut für Engineering, Elektronik und Analytik (ZEA), Forschungszentrum Jülich GmbH, Jülich, 52425, Germany
| | - Matthias Amann
- Jülich Centre for Neutron Science (JCNS) and Institute for Complex Systems (ICS), Forschungszentrum Jülich GmbH, Jülich, 52425, Germany
| | - Johan Buitenhuis
- Institute for Complex Systems (ICS), Forschungszentrum Jülich GmbH, Jülich, 52425, Germany
| | - Matthias Drochner
- Zentralinstitut für Engineering, Elektronik und Analytik (ZEA), Forschungszentrum Jülich GmbH, Jülich, 52425, Germany
| | - Ralf Engels
- Zentralinstitut für Engineering, Elektronik und Analytik (ZEA), Forschungszentrum Jülich GmbH, Jülich, 52425, Germany
| | - Romuald Hanslik
- Zentralinstitut für Engineering, Elektronik und Analytik (ZEA), Forschungszentrum Jülich GmbH, Jülich, 52425, Germany
| | - Günter Kemmerling
- Zentralinstitut für Engineering, Elektronik und Analytik (ZEA), Forschungszentrum Jülich GmbH, Jülich, 52425, Germany
| | - Peter Lindner
- Institut Laue-Langevin, 71 Avenue des Martyrs, Grenoble, 38000, France
| | - Aristeidis Papagiannopoulos
- Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, 48 Vass. Constantinou Avenue, Athens, 11635, Greece
| | - Vitaliy Pipich
- Jülich Centre for Neutron Science (JCNS), Outstation at MLZ, Forschungszentrum Jülich GmbH, Lichtenbergstrasse 1, Garching, 85747, Germany
| | - Lutz Willner
- Jülich Centre for Neutron Science (JCNS) and Institute for Complex Systems (ICS), Forschungszentrum Jülich GmbH, Jülich, 52425, Germany
| | - Henrich Frielinghaus
- Jülich Centre for Neutron Science (JCNS), Outstation at MLZ, Forschungszentrum Jülich GmbH, Lichtenbergstrasse 1, Garching, 85747, Germany
| | - Dieter Richter
- Jülich Centre for Neutron Science (JCNS) and Institute for Complex Systems (ICS), Forschungszentrum Jülich GmbH, Jülich, 52425, Germany
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23
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Plazzotta B, Dai J, Behrens MA, Furó I, Pedersen JS. Core Freezing and Size Segregation in Surfactant Core-Shell Micelles. J Phys Chem B 2015; 119:10798-806. [PMID: 26226298 DOI: 10.1021/acs.jpcb.5b06041] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Nonionic surfactants containing poly(ethylene oxide) are chemically simple and biocompatible and form core-shell micelles at a wide range of conditions. For those reasons, they and their aggregates have been widely investigated. Recently, irregularities that were observed in the low-temperature behavior of surfactants of the kind [CH3(CH2)(n)O(CH2CH2O)(m)H], (abbreviated CnEm) were assigned to a freezing-melting phase transition in the micellar core. In this work we expand the focus from the case of single component systems to binary surfactant systems at temperatures between 1 and 15 °C. By applying small-angle X-ray scattering (SAXS), differential scanning calorimetry (DSC), nuclear magnetic resonance (NMR), and density measurements in pure C18E20 and C18E100 solutions and their mixtures, we show that core freezing/melting is also present in mixtures. Additionally, comparing SAXS data obtained from the mixture with those from the single components, it was possible to demonstrate that the phase transition leads to a reversible segregation of the surfactants from mixed micelles to distinct kinds of micelles of the two components.
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Affiliation(s)
- Beatrice Plazzotta
- †Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, Aarhus University, Gustav Wieds Vej 14, 8000 Aarhus C, Denmark
| | - Jing Dai
- ‡Division of Applied Physical Chemistry, Department of Chemistry, KTH Royal Institute of Technology, Teknikringen 36, S-10044 Stockholm, Sweden
| | - Manja A Behrens
- †Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, Aarhus University, Gustav Wieds Vej 14, 8000 Aarhus C, Denmark
| | - István Furó
- ‡Division of Applied Physical Chemistry, Department of Chemistry, KTH Royal Institute of Technology, Teknikringen 36, S-10044 Stockholm, Sweden
| | - Jan Skov Pedersen
- †Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, Aarhus University, Gustav Wieds Vej 14, 8000 Aarhus C, Denmark
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24
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Size characterization of commercial micelles and microemulsions by Taylor dispersion analysis. Int J Pharm 2015; 492:46-54. [DOI: 10.1016/j.ijpharm.2015.06.037] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2015] [Revised: 06/19/2015] [Accepted: 06/20/2015] [Indexed: 01/09/2023]
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25
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Topete A, Barbosa S, Taboada P. Intelligent micellar polymeric nanocarriers for therapeutics and diagnosis. J Appl Polym Sci 2015. [DOI: 10.1002/app.42650] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Antonio Topete
- Laboratorio de Inmunología, Departamento de Fisiología; Centro Universitario de Ciencias de la Salud, Universidad de Guadalajara; 44340 Guadalajara Jalisco Mexico
| | - Silvia Barbosa
- Grupo de Física de Coloides y Polímeros, Departamento de Física de la Materia Condensada; Universidad de Santiago de Compostela; 15782 Santiago de Compostela Spain
| | - Pablo Taboada
- Grupo de Física de Coloides y Polímeros, Departamento de Física de la Materia Condensada; Universidad de Santiago de Compostela; 15782 Santiago de Compostela Spain
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26
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Zinn T, Willner L, Pipich V, Richter D, Lund R. Effect of Core Crystallization and Conformational Entropy on the Molecular Exchange Kinetics of Polymeric Micelles. ACS Macro Lett 2015; 4:651-655. [PMID: 35596408 DOI: 10.1021/acsmacrolett.5b00197] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Here we systematically study the equilibrium molecular exchange kinetics of a series of amphiphilic n-alkyl-poly(ethylene oxide) (Cn-PEO) micelles containing partly crystallized cores. Using differential scanning calorimetry (DSC), we determined the melting transition and extracted the enthalpy of fusion, ΔHfus, of the n-alkyl chains inside the micellar core. Molecular exchange kinetics was measured below the melting point using a time-resolved small-angle neutron scattering technique (TR-SANS) based on mixing deuterated and proteated but otherwise identical micelles. Comparing both kinetic and thermodynamic data, we find that crystallinity within the micellar cores leads to significant enthalpic and the entropic contributions to the activation barrier for molecular exchange. While the former leads to an enhanced stability, the positive entropic gain favors the process. Interestingly, the entropic term contains an excess term beyond what is expected from the measured entropy of fusion. Based on calculations using the Rotational Isomeric State (RIS) model, we suggest that the excess entropy is due to the gain in conformational entropy upon releasing the chain from the confined state in the core. The study thus provides deep insight into the fundamental processes of micellar kinetics and which might be relevant also to other semicrystalline soft matter and biological systems including lipid membranes.
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Affiliation(s)
- Thomas Zinn
- Department of Chemistry, University of Oslo, Postboks 1033 Blindern, 0315 Oslo, Norway
| | - Lutz Willner
- Jülich Centre for Neutron Science JCNS and Institute for Complex Systems ICS, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
| | - Vitaliy Pipich
- Jülich Centre for Neutron Science JCNS, Forschungszentrum Jülich GmbH, Outstation at MLZ, Lichtenbergstrasse 1 85747 Garching, Germany
| | - Dieter Richter
- Jülich Centre for Neutron Science JCNS and Institute for Complex Systems ICS, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
| | - Reidar Lund
- Department of Chemistry, University of Oslo, Postboks 1033 Blindern, 0315 Oslo, Norway
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27
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Amann M, Willner L, Stellbrink J, Radulescu A, Richter D. Studying the concentration dependence of the aggregation number of a micellar model system by SANS. SOFT MATTER 2015; 11:4208-4217. [PMID: 25892401 DOI: 10.1039/c5sm00469a] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We present a small-angle neutron scattering (SANS) structural characterization of n-alkyl-PEO polymer micelles in aqueous solution with special focus on the dependence of the micellar aggregation number on increasing concentration. The single micellar properties in the dilute region up to the overlap concentration ϕ* are determined by exploiting the well characterized unimer exchange kinetics of the model system in a freezing and diluting experiment. The micellar solutions are brought to thermodynamic equilibrium at high temperatures, where unimer exchange is fast, and are then cooled to low temperatures and diluted to concentrations in the limit of infinite dilution. At low temperatures the kinetics, and therefore the key mechanism for micellar rearrangement, is frozen on the experimental time scale, thus preserving the micellar structure in the dilution process. Information about the single micellar structure in the semidilute and concentrated region are extracted from structure factor analysis at high concentrations where the micelles order into fcc and bcc close packed lattices and the aggregation number can be calculated by geometrical arguments. This approach enables us to investigate the aggregation behavior in a wide concentration regime from dilute to 6·ϕ*, showing a constant aggregation number with concentration over a large concentration regime up to a critical concentration about three times ϕ*. When exceeding this critical concentration, the aggregation number was found to increase with increasing concentration. This behavior is compared to scaling theories for star-like polymer micelles.
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Affiliation(s)
- Matthias Amann
- Jülich Centre for Neutron Science JCNS-1 & Institute of Complex Systems ICS-1, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany.
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28
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Zinn T, Willner L, Lund R. Nanoscopic confinement through self-assembly: crystallization within micellar cores exhibits simple Gibbs-Thomson behavior. PHYSICAL REVIEW LETTERS 2014; 113:238305. [PMID: 25526170 DOI: 10.1103/physrevlett.113.238305] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2014] [Indexed: 06/04/2023]
Abstract
It is well known that liquids confined to small nanoscopic pores and droplets exhibit thermal behavior very different from bulk samples. Less is known about liquids spontaneously confined through self-assembly into micellar structures. Here we demonstrate, using a very well-defined n-alkyl-poly(ethylene oxide) polymer system with a tunable structure, that n-alkane(s) forming 2-3 nm small micellar cores are affected considerably by confinement in the form of melting point depressions. Moreover, comparing the reduction in melting points, ΔT_{m}, determined through volumetric and calorimetric methods with the micellar core radius, R_{c}, obtained from small-angle x-ray scattering, we find excellent agreement with the well-known Gibbs-Thomson equation, ΔT_{m}∼R_{c}^{-1}. This demonstrates that the reduced size, i.e., the Laplace pressure, is the dominant parameter governing the melting point depression in micellar systems.
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Affiliation(s)
- Thomas Zinn
- Department of Chemistry, University of Oslo, P.O. Box 1033, Blindern, 0315 Oslo, Norway
| | - Lutz Willner
- Jülich Centre for Neutron Science (JCNS) and Institute for Complex Systems (ICS),Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
| | - Reidar Lund
- Department of Chemistry, University of Oslo, P.O. Box 1033, Blindern, 0315 Oslo, Norway
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