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Saini A, Wolff M. Macroscopic Alignment of Micellar Crystals with Magnetic Microshearing. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:3980-3986. [PMID: 30767539 DOI: 10.1021/acs.langmuir.8b03701] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The effect of small quantities of a magnetic polymer nanocomposite (formed by surfactant Pluronic F127 @ Fe3O4 nanoparticles of 10 and 30 nm diameters) on the crystallization behavior of Pluronic F127 micelles solvated by 20% in water was investigated in the vicinity of hydrophilic and hydrophobic interfaces. Introducing magnetic nanoparticle at the core imparts magnetic properties to the polymeric micelle and increases its hydrodynamic diameter. These magnetic polymer nanocomposites act as defects in the pluronic crystal and hinder crystallization in comparison to pure Pluronic F127 micelles' behavior. The magnetic field results in a motion of the magnetic micelles and a microshearing effect. This microshearing assists in self-organization of the crystal. Addition of magnetic micelles formed using 30 nm magnetite particles shows similar crystallization behavior, however, with an overall reduced crystallinity due to their significantly larger size compared to the lattice parameter and the dimension of the interstitial cavity for an fcc structure.
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Affiliation(s)
- Apurve Saini
- Department of Physics and Astronomy , Uppsala University , Uppsala 75120 , Sweden
| | - Max Wolff
- Department of Physics and Astronomy , Uppsala University , Uppsala 75120 , Sweden
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Wolff M, Saini A, Simonne D, Adlmann F, Nelson A. Time Resolved Polarised Grazing Incidence Neutron Scattering from Composite Materials. Polymers (Basel) 2019; 11:polym11030445. [PMID: 30960429 PMCID: PMC6473511 DOI: 10.3390/polym11030445] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Revised: 02/27/2019] [Accepted: 03/04/2019] [Indexed: 11/30/2022] Open
Abstract
Neutron scattering experiments are a unique tool in material science due to their sensitivity to light elements and magnetic induction. However, for kinetic studies the low brilliance at existing sources poses challenges. In the case of periodic excitations these challenges can be overcome by binning the scattering signal according to the excitation state of the sample. To advance into this direction we have performed polarised and time resolved grazing incidence neutron scattering measurements on an aqueous solution of the polymer F127 mixed with magnetic nano-particles. Magnetic nano-composites like this provide magnetically tuneable properties of the polymer crystal as well as magnetic meta-crystals. Even though the grazing incidence small angle scattering and polarised signals are too weak to be evaluated at this stage we demonstrate that such experiments are feasible. Moreover, we show that the intensity of the 111 Bragg peak of the fcc micellar crystal depends on the actual shear rate, with the signal being maximised when the shear rate is lowest (and vice-versa).
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Affiliation(s)
- Maximilian Wolff
- Department for Physics and Astronomy, Uppsala University, Lägerhyddsvägen 1, 752 37 Uppsala, Sweden.
| | - Apurve Saini
- Department for Physics and Astronomy, Uppsala University, Lägerhyddsvägen 1, 752 37 Uppsala, Sweden.
| | - David Simonne
- Department for Physics and Astronomy, Uppsala University, Lägerhyddsvägen 1, 752 37 Uppsala, Sweden.
| | - Franz Adlmann
- Department for Physics and Astronomy, Uppsala University, Lägerhyddsvägen 1, 752 37 Uppsala, Sweden.
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Welbourn RJL, Bartholomew F, Gutfreund P, Clarke SM. Neutron Reflectometry of an Anionic Surfactant at the Solid-Liquid Interface under Shear. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:5982-5990. [PMID: 28530832 DOI: 10.1021/acs.langmuir.7b00530] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Neutron reflectometry with in situ rheology is used to measure the shear response of an adsorbed anionic surfactant (sodium bis(2-ethylhexyl) sulfosuccinate, AOT) at the alumina-water interface. A low surfactant concentration is measured where a single bilayer adsorbs at the interface as well as a higher concentration where a multilamellar structure forms. The low concentration structure does not change with the imposed shear (oscillatory or steady). However, the lamellar phase shows a loss of structure under both steady and oscillatory shear. There are differences between the steady and oscillatory cases, which are discussed, with both showing a strong dependence on the strain amplitude.
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Affiliation(s)
- Rebecca J L Welbourn
- BP Institute and Department of Chemistry, University of Cambridge , Madingley Rise, Madingley Road, Cambridge, U.K
| | - Felicity Bartholomew
- BP Institute and Department of Chemistry, University of Cambridge , Madingley Rise, Madingley Road, Cambridge, U.K
| | | | - Stuart M Clarke
- BP Institute and Department of Chemistry, University of Cambridge , Madingley Rise, Madingley Road, Cambridge, U.K
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Penfold J, Thomas RK, Li P, Petkov JT, Tucker I, Cox AR, Hedges N, Webster JRP, Skoda MWA. Impact of the degree of ethoxylation of the ethoxylated polysorbate nonionic surfactant on the surface self-assembly of hydrophobin-ethoxylated polysorbate surfactant mixtures. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:9741-9751. [PMID: 25046802 DOI: 10.1021/la5022627] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Neutron reflectivity measurements have been used to study the surface adsorption of the polyethylene sorbitan monostearate surfactant, with degrees of ethoxylation varying from 3 to 20 ethylene oxide groups, with the globular protein hydrophobin. The surface interaction between the ethoxylated polysorbate nonionic surfactants and the hydrophobin results in self-assembly at the air-solution interface in the form of a well-defined layered surface structure. The surface interaction arises from a combination of the hydrophobic interaction between the surfactant alkyl chain and the hydrophobic patch on the surface of the hydrophobin, and the hydrophilic interaction between the ethoxylated sorbitan headgroup and the hydrophilic regions on the surface of the hydrophobin. The results presented show that varying the degree of ethoxylation of the polysorbate surfactant changes the interaction between the surfactant and the hydrophobin and the packing, and hence the evolution in the resulting surface structure. The optimal degree of ethoxylation for multilayer formation is over a broad range, from of order 6 to 17 ethylene oxide groups, and for degrees of ethoxylation of 3 and 20 only monolayer adsorption of either the surfactant or the hydrophobin is observed.
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Affiliation(s)
- Jeffrey Penfold
- Physical and Theoretical Chemistry Laboratory, Oxford University , South Parks Road, Oxford OX1 2JD, United Kingdom
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Penfold J, Thomas RK. Neutron reflectivity and small angle neutron scattering: An introduction and perspective on recent progress. Curr Opin Colloid Interface Sci 2014. [DOI: 10.1016/j.cocis.2014.01.002] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Wolff M, Kuhns P, Liesche G, Ankner JF, Browning JF, Gutfreund P. Combined neutron reflectometry and rheology. J Appl Crystallogr 2013. [DOI: 10.1107/s0021889813024059] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Neutron reflectometry has been combined with rheology in order to investigate the solid boundary of liquids and polymers under shear deformation. This approach allows one to apply a controlled stress to a material while resolving the structural arrangements on the sub-nanometre length scale with neutron reflectivity, off-specular scattering and small-angle scattering at the same time. The specularly reflected neutron intensity of a 20% by weight solution of Pluronic F127 in deuterated water in contact with an octadecyl trichlorosilane-covered and a piranha-treated silicon wafer is evaluated. A pronounced difference is found in the structure formed by the polymer micelles at the two surfaces, which is explained by the difference in the affinity of the micellar shell to the solid interfaces. Under deformation, the near interface structure changes at deformations of about 2, 30 and 900%. The structural changes are correlated with changes in the storage and loss modulus of the polymer solution, revealing a transition from more solid to more liquid like properties.
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Gutfreund P, Wolff M, Maccarini M, Gerth S, Ankner JF, Browning J, Halbert CE, Wacklin H, Zabel H. Depletion at solid/liquid interfaces: flowing hexadecane on functionalized surfaces. J Chem Phys 2011; 134:064711. [PMID: 21322725 DOI: 10.1063/1.3549895] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We present a neutron reflectivity study on interfaces in contact with flowing hexadecane, which is known to exhibit surface slip on functionalized solid surfaces. The single crystalline silicon substrates were either chemically cleaned Si(100) or Si(100) coated by octadecyl-trichlorosilane (OTS), which resulted in different interfacial energies. The liquid was sheared in situ and changes in reflectivity profiles were compared to the static case. For the OTS surface, the temperature dependence was also recorded. For both types of interfaces, density depletion of the liquid at the interface was observed. In the case of the bare Si substrate, shear load altered the structure of the depletion layer, whereas for the OTS covered surface no effect of shear was observed. Possible links between the depletion layer and surface slip are discussed. The results show that, in contrast to water, for hexadecane the enhancement of the depletion layer with temperature and interfacial energy reduces the amount of slip. Thus a density depletion cannot be the origin of surface slip in this system.
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Affiliation(s)
- Philipp Gutfreund
- Institut für Festkörperphysik, Ruhr-Universität Bochum, 44780 Bochum, Germany.
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Wolff M, Gutfreund P, Rühm A, Akgun B, Zabel H. Nanoscale discontinuities at the boundary of flowing liquids: a look into structure. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:184102. [PMID: 21508468 DOI: 10.1088/0953-8984/23/18/184102] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
When downsizing technology, confinement and interface effects become enormously important. Shear imposes additional anisotropy on a liquid. This may induce inhomogeneities, which may have their origin close to the solid interface. For advancing the understanding of flow, information on structures on all length scales and in particular close to the solid interface is indispensable. Neutron scattering offers an excellent tool to contribute in this context. In this work, surface sensitive scattering techniques were used to resolve the structure of liquids under flow in the vicinity of a solid interface. Our results are summarized as follows. First, for a Newtonian liquid we report a depletion distance on the order of nanometers which is far too small to explain the amount of surface slip, on the order of micrometers, found by complementary techniques. Second, for a grafted polymer brush we find no entanglement-disentanglement transition under shear but the grafted film gets ripped off the surface. Third, by evaluating the local structure factor of a micellar solution close to the solid interface it turns out that the degree of order and local relaxation depends critically on the surface energy of the solid surface.
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Affiliation(s)
- Max Wolff
- Department of Physics and Astronomy, Uppsala University, Uppsala 75121, Sweden.
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Walz M, Wolff M, Voss N, Zabel H, Magerl A. Micellar crystallization with a hysteresis in temperature. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:14391-14394. [PMID: 20722428 DOI: 10.1021/la102415x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
We have investigated the phase diagram of the triblock copolymer P123 solved in water by viscosity measurements for different concentrations and temperatures. The structures of the different phases were identified by surface sensitive neutron diffraction. We find a pronounced hysteresis between heating and cooling. During heating, a highly viscous crystalline fcc phase is found before melting occurs at 44 °C with a simultaneous drop in viscosity. Upon cooling, first a hexagonal phase with low viscosity develops followed by a highly viscous fcc phase. Phase diagrams for the heating and cooling cycle for different concentrations are provided. The hysteric behavior is discussed in relation to the shape of the micelles.
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Affiliation(s)
- Marco Walz
- Crystallography and Structural Physics, University of Erlangen-Nürnberg, Staudtstrasse 3, 91058 Erlangen, Germany.
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Sasa LA, Yearley EJ, Welch CF, Taylor MA, Gilbertson RD, Hammeter C, Majewski J, Hjelm RP. The Los Alamos Neutron Science Center neutron rheometer in the cone and plate geometry to examine tethered polymers/polymer melt interfaces via neutron reflectivity. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2010; 81:055102. [PMID: 20515167 DOI: 10.1063/1.3381037] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Although several other neutron rheometers have been built to study soft matter under nonequilibrium conditions, none of them have the ability to measure the structure and behavior of the polymeric interfacial regions in highly viscous polymer melts which require high torques/high strain rates and high temperatures. A neutron rheometer in the cone and plate geometry has been constructed at the Los Alamos Neutron Science Center to rectify this lack of experimental instrumentation. It is also the first-of-its-kind to perform neutron reflectivity studies concurrently with rheological measurements. The details of both the development and testing of the Los Alamos Neutron Science Center neutron rheometer in the cone and plate configuration are described. Proof of principle neutron reflectivity results of end-grafted polystyrene against an identical melt under shear are presented, showing qualitatively that the structural attributes of the end-grafted polymer change when exposed to shear.
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Affiliation(s)
- Leslie A Sasa
- Los Alamos Neutron Scattering Center, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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Yearley EJ, Sasa LA, Welch CF, Taylor MA, Kupcho KM, Gilbertson RD, Hjelm RP. The Couette configuration of the Los Alamos Neutron Science Center neutron rheometer for the investigation of polymers in the bulk via small-angle neutron scattering. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2010; 81:045109. [PMID: 20441370 DOI: 10.1063/1.3374121] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
A neutron rheometer in the Couette geometry has been built at the Los Alamos Neutron Science Center to examine the molecular steady-state and dynamic responses of entangled polymeric materials in the bulk under the application of shear stress via small-angle neutron scattering. Although similar neutron rheometers have been fabricated elsewhere, this new design operates under the extreme conditions required for measuring the structure and behavior of high molecular weight polymer melts. Specifically, the rheometer achieves high torques (200 N m) and shear rates (865 s(-1)) simultaneously, never before attainable with other neutron rheometers at temperatures up to 240 degrees C under an inert gas environment. The design of the instrument is such that relatively small sample sizes are required. The testing of the Los Alamos Neutron Science Center Neutron Rheometer in the Couette design both as a rheometer and in the small-angle neutron optical configuration on highly viscous polystyrene is presented. The observed anisotropic neutron scattering pattern of the polystyrene melt at a molecular weight above entanglement provides evidence that the conformation of the polymer chains are elongated in the direction of the melt flow, in agreement with the current theories concerning linear polymers in the bulk.
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Affiliation(s)
- Eric J Yearley
- Los Alamos Neutron Scattering Center, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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