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Geonzon LC, Kobayashi M, Sugimoto T, Adachi Y. Interaction between silica particles with poly(ethylene oxide) studied using an optical tweezer: insignificant effect of poly(ethylene oxide) on long-range double layer interaction. Colloid Polym Sci 2022. [DOI: 10.1007/s00396-022-05020-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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2
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Effects of Al(III) Ions at Magnetite Flotation from Quartz by Dodecylamine Al(III). MINERALS 2022. [DOI: 10.3390/min12050613] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
The flotation separation of magnetite and quartz is a long-term challenge for the beneficiation industry. For high-quartz magnetite, conventional flotation shows poor separation effect, resulting in the waste of resources and low flotation efficiency. In this paper, dodecylamine acts as a collector and Al(III) ions in water act as a depressant to selectively separate magnetite and quartz at high alkalinity. The experimental results are analyzed by a micro-flotation experiment, solution chemical calculation, zeta potential, contact angle measurement, and Fourier transform infrared spectroscopy (FTIR). The results of micro-flotation experiments showed that Al(III) ions in water inhibited magnetite more strongly than quartz. The calculation results of solution stoichiometry and zeta potential showed that the phase formed by Al(III) ions on the surface of magnetite and quartz are mainly Al(OH)3(s), which covers the surface of magnetite and quartz, The contact angle measurement results showed that with the addition of Al(III) ions, the contact angle of magnetite varies significantly than that of quartz, and the floatability of magnetite is lower than that of quartz. The FT-IR results further indicated that the addition of Al(III) ions could hinder the adsorption of dodecylamine on the magnetite surface. Meanwhile, the addition of Al(III) ions has no obvious effect on the adsorption of dodecylamine on the quartz surface.
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3
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Lundberg DJ, Strano MS. Approximate Corona Phase Hamiltonian for Individual Cylindrical Nanoparticle-Polymer Interactions. J Phys Chem B 2021; 126:347-354. [PMID: 34962804 DOI: 10.1021/acs.jpcb.1c09998] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Nanoparticle surfaces, such as cylindrical nanowires and carbon nanotubes, are commonly coated with adsorbed polymer corona phases to impart solution stabilization and to control molecular interactions. These adsorbed polymer molecules (biological or otherwise), also known as the corona phase, are critical to engineering particle and molecular interactions. However, the prediction of its structure and the corresponding properties remains an unresolved problem in polymer physics. In this work, we construct a Hamiltonian describing the adsorption of an otherwise linear polymer to the surface of a cylindrical nanorod in the form of an integral equation summing up the energetic contributions corresponding to polymer bending, confinement, solvation, and electrostatics. We introduce an approximate functional that allows for the solution of the minimum energy configuration in the strongly bound limit. The functional is shown to predict the pitch and surface area of observed helical corona phases in the literature based on the surface binding energy and persistence length alone. This approximate functional also predicts and quantitatively describes the recently observed ionic strength-mediated phase transitions of charged polymer corona at carbon nanotube surfaces. The Hamiltonian and the approximate functional provide the first theoretical link between the polymer's mechanical and chemical properties and the resulting adsorbed phase configuration and therefore should find widespread utility in predicting corona phase structures around anisotropic nanoparticles.
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Affiliation(s)
- Daniel James Lundberg
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Michael S Strano
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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4
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Lehtonen J, Chen X, Beaumont M, Hassinen J, Orelma H, Dumée LF, Tardy BL, Rojas OJ. Impact of incubation conditions and post-treatment on the properties of bacterial cellulose membranes for pressure-driven filtration. Carbohydr Polym 2021; 251:117073. [PMID: 33142618 DOI: 10.1016/j.carbpol.2020.117073] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Revised: 08/13/2020] [Accepted: 09/05/2020] [Indexed: 12/17/2022]
Abstract
Bacterial cellulose (BC) has shown potential as a separation material. Herein, the performance of BC in pressure-driven separation is investigated as a function of incubation conditions and post-culture treatment. The pure water flux of never-dried BC (NDBC), was found to be 9 to 16 times higher than that for dried BC (DBC), in a pressure range of 0.25 to 2.5 bar. The difference in pressure response of NDBC and DBC was observed both in cross-flow filtration and capillary flow porometry experiments. DBC and NDBC were permeable to polymers with a hydrodynamic radius of ∼60 nm while protein retention was possible by introducing anionic surface charges on BC. The results of this work are expected to expand the development of BC-based filtration membranes, for instance towards the processing of biological fluids.
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Affiliation(s)
- Janika Lehtonen
- Department of Bioproducts and Biosystems, School of Chemical Engineering, Aalto University, P. O. Box 16300, FI-00076 Aalto, Espoo, Finland
| | - Xiao Chen
- Deakin University, Geelong, Institute for Frontier Materials, Waurn Ponds, Victoria 3216, Australia
| | - Marco Beaumont
- Department of Bioproducts and Biosystems, School of Chemical Engineering, Aalto University, P. O. Box 16300, FI-00076 Aalto, Espoo, Finland
| | - Jukka Hassinen
- Department of Bioproducts and Biosystems, School of Chemical Engineering, Aalto University, P. O. Box 16300, FI-00076 Aalto, Espoo, Finland
| | - Hannes Orelma
- VTT - Technical Research Centre of Finland, Tietotie 4E, P.O. Box 1000, FI-02044 Espoo, Finland
| | - Ludovic F Dumée
- Deakin University, Geelong, Institute for Frontier Materials, Waurn Ponds, Victoria 3216, Australia; Khalifa University, Department of Chemical Engineering, Abu Dhabi, United Arab Emirates; Center for Membrane and Advanced Water Technology, Khalifa University, Abu Dhabi, United Arab Emirates.
| | - Blaise L Tardy
- Department of Bioproducts and Biosystems, School of Chemical Engineering, Aalto University, P. O. Box 16300, FI-00076 Aalto, Espoo, Finland.
| | - Orlando J Rojas
- Department of Bioproducts and Biosystems, School of Chemical Engineering, Aalto University, P. O. Box 16300, FI-00076 Aalto, Espoo, Finland; Departments of Chemical & Biological Engineering, Chemistry, and Wood Science, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.
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6
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Elliott LN, Behra JS, Hondow N, Bourne RA, Hassanpour A, Edwards JL, Sutcliffe S, Hunter TN. Characterisation of polyphosphate coated aluminium-doped titania nanoparticles during milling. J Colloid Interface Sci 2019; 548:110-122. [PMID: 30986710 DOI: 10.1016/j.jcis.2019.04.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Revised: 04/02/2019] [Accepted: 04/03/2019] [Indexed: 11/19/2022]
Abstract
This paper investigates the characterisation of alumina-doped titania nanoparticles, milled under high-shear over time, in the presence of sodium hexametaphosphate (SHMP) dispersant. Transmission electron microscopy (TEM) indicated that prolonged milling times led to the formation of 10 nm particle fines which were electrostatically attracted to larger particles, where no change in the crystal structure was observed. Primary particle sizes measured by dynamic light scattering (DLS) and TEM were in agreement and showed no change in primary particle size (∼250 nm) with respect to milling time, however, there was a clear reduction in the magnitude of the slow mode decay associated to aggregates. The TiO2 was found to have an isoelectric point (iep) in the range of pH 3-4.5, where an increase in milling time led to a lower pHiep, indicative of an increase in SHMP coverage, which was further supported by an intensification in phosphorus content measured by X-ray fluorescence (XRF). Phosphorus content and zeta potential analysis before and after centrifugal washing showed that SHMP was partially removed or hydrolysed for the longer milled pigment samples, whereas no change was observed for shorter milled samples. Relaxation NMR was also performed, where enhanced relaxation rates at longer milling times were associated partially to increases in surface area and exposure of Al sites, as well as physicochemical changes to SHMP density and structure. It is thought that extended milling times may lead to hydrolysis or other structural changes of the dispersant from the high energy milling conditions, allowing easier removal after washing for longer milled pigments.
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Affiliation(s)
- Laura N Elliott
- School of Chemical and Process Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom; Centre for Doctoral Training in Complex Particulate Products and Processes, University of Leeds, United Kingdom.
| | - Juliette S Behra
- School of Chemical and Process Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Nicole Hondow
- School of Chemical and Process Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Richard A Bourne
- School of Chemical and Process Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom; Institute of Process Research and Development, School of Chemistry, University of Leeds, United Kingdom
| | - Ali Hassanpour
- School of Chemical and Process Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - John L Edwards
- Venator, Titanium House, Hanzard Drive, Wynyard Park, Stockton-on-Tees TS22 5FD, United Kingdom
| | - Stephen Sutcliffe
- Venator, Titanium House, Hanzard Drive, Wynyard Park, Stockton-on-Tees TS22 5FD, United Kingdom
| | - Timothy N Hunter
- School of Chemical and Process Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom
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7
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Effects of Cations/Anions in Recycled Tailing Water on Cationic Reverse Flotation of Iron Oxides. MINERALS 2019. [DOI: 10.3390/min9030161] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
It is well known that reverse flotation performance of iron oxides is affected by water quality. Since many potential variations among water sources recycling in a mineral processing plant bring unpredictable effects on the flotation system of iron oxides: disturbing ions/compounds, pH, hardness, residual reagents, etc. In this study, the recycled tailing water from a local plant, characteristically constituting of Ca2+, Mg2+, Na+, K+, Al3+, Fe3+, Cl−, SO42− etc., was introduced into the cationic reverse flotation process of an iron ore. A series of bench flotation tests using iron ores, micro-flotation tests using pure fine quartz, water chemical analyses, and zeta potential measurement were conducted with the objective of identifying the possible influences of both cations and anions in the recycled tailing water on the flotation performance. The flotation results pointed out that the cation with higher valency had more severe influences on the recovery of iron oxides. The formation of the pH-dependent surface complexes on mineral surfaces, for example, Fe(OH)+, Fe(OH)2+, and Fe(OH)3 resulted from Fe3+ ions adsorption, contributed to the less negative zeta potentials of the quartz, and consequently weakened its interaction with the amine collector. It is worthy to note that SO42− ions seem to have a more positive effect on the recovery of iron oxides than Cl− ions. This is probably attributed to the formation of inner/outer- sphere surface complexes on the iron oxides, inhibiting the dissolution of the iron ions/species, and the coordination with these cations from the recycled tailing water, shielding their disturbances in the flotation.
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8
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Wang C, Yan F, Meng X, Qiao Y, Qiu D. Regulating polymer adsorption on colloid by surface morphology. SOFT MATTER 2018; 14:9336-9342. [PMID: 30310912 DOI: 10.1039/c8sm01833b] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The study of polymer adsorption on colloidal particles has attracted intensive attention. In this work, we investigated polymer adsorption on substrate colloidal particles with two complementary morphologies, one of which has bulges (raspberry-like) on the surface and the other of which has holes instead (strawberry-like). Compared to the bulges, the holes on the colloidal particles were found to prevent polymer adsorption and this effect was dependent on the relative dimensions of the polymer coil and hole. This surface morphology effect was attributed mainly to the reduced polymer accessibility to the adsorption sites in holes when the hydrodynamic size of the polymer coil is larger than the hole, due to the size limiting effect. When the hydrodynamic size of the polymer coil is smaller than that of the holes, no difference in polymer adsorption was observed between raspberry-like and strawberry-like colloids. This study provides a strategy for regulating polymer adsorption on colloidal particles by adjusting the fine structures on the surface, which may be advantageous when limited chemical compositions are allowed. For example, protein adsorption on colloidal drugs may be found to be significantly reduced when colloids with surface holes are used.
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Affiliation(s)
- Chao Wang
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Polymer Physics and Chemistry, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
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9
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Salt enhanced solvent relaxation and particle surface area determination via rapid spin-lattice NMR. POWDER TECHNOL 2018. [DOI: 10.1016/j.powtec.2018.04.050] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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10
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The role of copolymer composition on the specific ion and thermo-response of ethylene glycol-based brushes. POLYMER 2018. [DOI: 10.1016/j.polymer.2018.01.053] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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11
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Bodratti AM, Sarkar B, Alexandridis P. Adsorption of poly(ethylene oxide)-containing amphiphilic polymers on solid-liquid interfaces: Fundamentals and applications. Adv Colloid Interface Sci 2017; 244:132-163. [PMID: 28069108 DOI: 10.1016/j.cis.2016.09.003] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Revised: 09/23/2016] [Accepted: 09/23/2016] [Indexed: 12/30/2022]
Abstract
The adsorption of amphiphilic molecules of varying size on solid-liquid interfaces modulates the properties of colloidal systems. Nonionic, poly(ethylene oxide) (PEO)-based amphiphilic molecules are particularly useful because of their graded hydrophobic-hydrophilic nature, which allows for adsorption on a wide array of solid surfaces. Their adsorption also results in other useful properties, such as responsiveness to external stimuli and solubilization of hydrophobic compounds. This review focuses on the adsorption properties of PEO-based amphiphiles, beginning with a discussion of fundamental concepts pertaining to the adsorption of macromolecules on solid-liquid interfaces, and more specifically the adsorption of PEO homopolymers. The main portion of the review highlights studies on factors affecting the adsorption and surface self-assembly of PEO-PPO-PEO block copolymers, where PPO is poly(propylene oxide). Block copolymers of this type are commercially available and of interest in several fields, due to their low toxicity and compatibility in aqueous systems. Examples of applications relevant to the interfacial behavior of PEO-PPO-PEO block copolymers are paints and coatings, detergents, filtration, and drug delivery. The methods discussed herein for manipulating the adsorption properties of PEO-PPO-PEO are emphasized for their ability to shed light on molecular interactions at interfaces. Knowledge of these interactions guides the formulation of novel materials with useful mesoscale organization and micro- and macrophase properties.
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12
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Huang YR, Lamson M, Matyjaszewski K, Tilton RD. Enhanced interfacial activity of multi-arm poly(ethylene oxide) star polymers relative to linear poly(ethylene oxide) at fluid interfaces. Phys Chem Chem Phys 2017; 19:23854-23868. [DOI: 10.1039/c7cp02841e] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Interfacial tension reduction, dynamic dilatational elasticity and extent of adsorption were investigated for linear poly(ethylene oxide) (PEO) chains of varying molecular weight and for PEO star polymers with an average of 64 arms per star at air/water, xylene/water, and cyclohexane/water interfaces.
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Affiliation(s)
- Yun-Ru Huang
- Center for Complex Fluids Engineering
- Department of Chemical Engineering
- Carnegie Mellon University
- Pittsburgh
- USA
| | - Melissa Lamson
- Center for Complex Fluids Engineering
- Department of Chemistry
- Carnegie Mellon University
- Pittsburgh
- USA
| | - Krzysztof Matyjaszewski
- Center for Complex Fluids Engineering
- Department of Chemistry
- Carnegie Mellon University
- Pittsburgh
- USA
| | - Robert D. Tilton
- Center for Complex Fluids Engineering
- Department of Chemical Engineering
- Carnegie Mellon University
- Pittsburgh
- USA
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13
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Effect of particle/polymer number ratio on the structure and dynamics of complex between large polymer and nanoparticle. Colloids Surf A Physicochem Eng Asp 2016. [DOI: 10.1016/j.colsurfa.2016.07.080] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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14
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Kalasin S, Santore MM. Near-Surface Motion and Dynamic Adhesion during Silica Microparticle Capture on a Polymer (Solvated PEG) Brush via Hydrogen Bonding. Macromolecules 2015. [DOI: 10.1021/acs.macromol.5b01977] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Affiliation(s)
- Surachate Kalasin
- Department of Polymer Science
and Engineering, University of Massachusetts, 120 Governors Drive, Amherst, Massachusetts 01003, United States
| | - Maria M. Santore
- Department of Polymer Science
and Engineering, University of Massachusetts, 120 Governors Drive, Amherst, Massachusetts 01003, United States
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15
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Bodratti AM, Wu J, Jahan R, Sarkar B, Tsianou M, Alexandridis P. Mono- and Di-valent Salts as Modifiers of PEO-PPO-PEO Block Copolymer Interactions with Silica Nanoparticles in Aqueous Dispersions. J DISPER SCI TECHNOL 2015. [DOI: 10.1080/01932691.2015.1011273] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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16
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Qiao XG, Dugas PY, Charleux B, Lansalot M, Bourgeat-Lami E. Synthesis of Multipod-like Silica/Polymer Latex Particles via Nitroxide-Mediated Polymerization-Induced Self-Assembly of Amphiphilic Block Copolymers. Macromolecules 2015. [DOI: 10.1021/ma5019473] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- X. G. Qiao
- Univ. Lyon
1, CPE Lyon, CNRS,
UMR 5265, Laboratoire de Chimie, Catalyse, Polymères et Procédés
(C2P2), LCPP group, Université de Lyon, 43, Bd. du 11 Novembre
1918, F-69616 Villeurbanne, France
| | - P.-Y. Dugas
- Univ. Lyon
1, CPE Lyon, CNRS,
UMR 5265, Laboratoire de Chimie, Catalyse, Polymères et Procédés
(C2P2), LCPP group, Université de Lyon, 43, Bd. du 11 Novembre
1918, F-69616 Villeurbanne, France
| | - B. Charleux
- Univ. Lyon
1, CPE Lyon, CNRS,
UMR 5265, Laboratoire de Chimie, Catalyse, Polymères et Procédés
(C2P2), LCPP group, Université de Lyon, 43, Bd. du 11 Novembre
1918, F-69616 Villeurbanne, France
| | - M. Lansalot
- Univ. Lyon
1, CPE Lyon, CNRS,
UMR 5265, Laboratoire de Chimie, Catalyse, Polymères et Procédés
(C2P2), LCPP group, Université de Lyon, 43, Bd. du 11 Novembre
1918, F-69616 Villeurbanne, France
| | - E. Bourgeat-Lami
- Univ. Lyon
1, CPE Lyon, CNRS,
UMR 5265, Laboratoire de Chimie, Catalyse, Polymères et Procédés
(C2P2), LCPP group, Université de Lyon, 43, Bd. du 11 Novembre
1918, F-69616 Villeurbanne, France
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17
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Zhao C, Tong K, Tan J, Liu Q, Wu T, Sun D. Colloidal properties of montmorillonite suspensions modified with polyetheramine. Colloids Surf A Physicochem Eng Asp 2014. [DOI: 10.1016/j.colsurfa.2014.05.052] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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18
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de Vos WM, Cattoz B, Avery MP, Cosgrove T, Prescott SW. Adsorption and surfactant-mediated desorption of poly(vinylpyrrolidone) on plasma- and piranha-cleaned silica surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:8425-8431. [PMID: 25007346 DOI: 10.1021/la501877v] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Optical flow cell reflectometry was used to study the adsorption of poly(vinylpyrrolidone) (PVP) to a silica surface and the subsequent surfactant adsorption and polymer desorption upon exposure to the anionic surfactant sodium dodecyl sulfate (SDS). We have studied these effects as a function of pH and surfactant concentration, but also for two different methods of silica preparation, O2 plasma and piranha cleaning. As a function of pH, a plateau in the amount adsorbed of ∼0.6 mg/m(2) is observed below a critical pH, above which the adsorption decreases to zero within 2-3 pH units. An increase in pH leads to dissociation of surface OH groups and a decreased potential for hydrogen bonding between the polymer and surface. For the plasma- and piranha-cleaned silica, the critical pH differs by 1-2 pH units, a reflection of the much larger amount of surface OH groups on piranha-cleaned silica (for a given pH). Subsequent rinsing of the adsorbed layer of PVP with an SDS solution leads to total or partial desorption of the PVP layer. Any remaining adsorbed PVP then acts as an adsorption site for SDS. A large difference between plasma- and piranha-cleaned silica is observed, with the PVP layer adsorbed to plasma-cleaned silica being much more susceptible to desorption by SDS. For a plasma-cleaned surface at pH 5.5, only 30% of the originally adsorbed PVP is remaining, while for piranha-cleaned silica, the pH can be increased to 10 before a similar reduction in the amount of adsorbed PVP is seen. For a given pH, piranha-cleaned silica has a higher surface charge, leading to a smaller amount of adsorbed SDS per PVP chain on a piranha-cleaned surface compared to a plasma-cleaned surface under identical conditions. In that way, the high negative surface charge makes desorption by negatively charged SDS more difficult. The high surface charge thus protects the neutral polymer from surfactant-mediated desorption.
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Affiliation(s)
- Wiebe M de Vos
- School of Chemistry, University of Bristol , Cantock's Close, Bristol BS8 1TS, U.K
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19
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Saigal T, Riley JK, Golas PL, Bodvik R, Claesson PM, Matyjaszewski K, Tilton RD. Poly(ethylene oxide) star polymer adsorption at the silica/aqueous interface and displacement by linear poly(ethylene oxide). LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:3999-4007. [PMID: 23448185 DOI: 10.1021/la305085a] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Multiarm star copolymers with approximately 460 poly(ethylene oxide) (PEO) arms that have a degree of polymerization N = 45 were synthesized via atom transfer radical polymerization (ATRP) of PEO-methacrylate macromonomers in the presence of divinyl benzene cross-linkers. These are an example of molecular or nanoparticulate brushes that are of interest as steric stabilizers or boundary lubrication agents when adsorbed from solution to a solid/aqueous interface. We use ellipsometry to measure adsorption isotherms at the silica/aqueous interface for PEO star polymers and linear PEO chains having molecular weights comparable either to the star polymer or to the individual arms. The compactness of the PEO star polymers (molecular weight 1.2 × 10(6)) yields a saturation surface excess concentration that is approximately 3.5 times greater than that of the high molecular weight (1 × 10(6)) linear PEO. Adsorption of low molecular weight (6000) linear PEO was below the detection limit. Competitive adsorption experiments were conducted with ellipsometry, complemented by independent quartz crystal microbalance with dissipation (QCM-D) measurements. Linear PEO (high molecular weight) displaced preadsorbed PEO star polymers over the course of approximately 1.5 h, to form a mixed adsorbed layer having not only a significantly lower overall polymer surface excess concentration, but also a significantly greater amount of hydrodynamically entrapped water. Challenging a preadsorbed linear PEO (high molecular weight) layer with PEO star polymers produced no measurable change in the overall polymer surface excess concentration, but changes in the QCM-D energy dissipation and resonance frequency suggested that the introduction of PEO star polymers caused a slight swelling of the layer with a correspondingly small increase in entrapped water content.
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Affiliation(s)
- Trishna Saigal
- Center for Complex Fluids Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
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20
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Robbes AS, Cousin F, Meneau F, Dalmas F, Schweins R, Gigmes D, Jestin J. Polymer-Grafted Magnetic Nanoparticles in Nanocomposites: Curvature Effects, Conformation of Grafted Chain, and Bimodal Nanotriggering of Filler Organization by Combination of Chain Grafting and Magnetic Field. Macromolecules 2012. [DOI: 10.1021/ma301927e] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
- Anne-Sophie Robbes
- Laboratoire Léon Brillouin, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France
- Synchrotron SOLEIL, L’Orme des Merisiers, PO Box 48, Saint-Aubin,
91192 Gif sur Yvette, France
| | - Fabrice Cousin
- Laboratoire Léon Brillouin, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France
| | - Florian Meneau
- Synchrotron SOLEIL, L’Orme des Merisiers, PO Box 48, Saint-Aubin,
91192 Gif sur Yvette, France
| | - Florent Dalmas
- Institut de Chimie et des Matériaux Paris-Est, UMR 7182 CNRS/Université Paris-Est, 2-8 rue
Henri Dunant 94320 Thiais, France
| | - Ralf Schweins
- Institut Laue Langevin (ILL), DS/LSS,
6 rue Jules Horowitz, 38042 Grenoble Cedex 9, France
| | - Didier Gigmes
- Institut de Chimie Radicalaire, UMR 7273 Aix-Marseille Université-CNRS, Av.
Esc. Normandie Niemen Service 542, 13397 Marseille Cedex 20, France
| | - Jacques Jestin
- Laboratoire Léon Brillouin, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France
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21
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Cattoz B, Cosgrove T, Crossman M, Prescott SW. Surfactant-mediated desorption of polymer from the nanoparticle interface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:2485-2492. [PMID: 22188133 DOI: 10.1021/la204512d] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The surfactant-mediated desorption of adsorbed poly(vinylpyrrolidone), PVP, from anionic silica surfaces by sodium dodecyl sulfate, SDS, was observed. While photon correlation spectroscopy shows that the size of the polymer-surfactant-particle ensemble grows with added SDS, a reduction in the near-surface polymer concentration is measured by solvent relaxation NMR. Volume fraction profiles of the polymer layer extracted from small-angle neutron scattering experiments illustrate that the adsorbed polymer layer has become more diffuse and the polymer chains more elongated as a result of the addition of SDS. The total adsorbed amount is shown to decrease due to Coulombic repulsion between the surfactant-polymer complexes and between the complexes and the anionic silica surface.
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Affiliation(s)
- Beatrice Cattoz
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK
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22
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Angelescu DG, Nylander T, Piculell L, Linse P, Lindman B, Tropsch J, Detering J. Adsorption of branched-linear polyethyleneimine-ethylene oxide conjugate on hydrophilic silica investigated by ellipsometry and Monte Carlo simulations. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:9961-9971. [PMID: 21755979 DOI: 10.1021/la2017209] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The adsorption of and conformation adopted by a branched-linear polymer conjugate to the hydrophilic silica-aqueous solution interface have been studied by in situ null ellipsometry and Monte Carlo simulations. The conjugate is a highly branched polyethyleneimine structure with ethyleneoxide chains grafted to its primary and secondary amino groups. In situ null ellipsometry demonstrated that the polymer conjugate adsorbs to the silica surface from water and aqueous solution of 1 mM asymmetric divalent salt (calcium and magnesium chloride to emulate hard water) over a large pH range. The adsorbed amount is hardly affected by pH and large charge reversal on the negatively charged silica surface occurred at pH = 4.0, due to the adsorption of the cationic polyelectrolyte. The Monte Carlo simulations using an appropriate coarse-grained model of the polymer in solution predicted a core-shell structure with no sharp boundary between the ethyleneimine and ethyleneoxide moieties. The structure at the interface is similar to that in solution when the polymer degree of protonation is low or moderate while at high degree of protonation the strong electrostatic attraction between the ethyleneimine core and oppositely charged silica surface distorts the ethyleneoxide shell so that an "anemone"-like configuration is adopted. The adsorption of alkyl benzene sulfonic acid (LAS) to a preadsorbed polymer layer was also investigated by null ellipsometry. The adsorption data brought additional support for the existence of a strong polymer adsorption and showed the presence of a binding which was further enhanced by the decreased solvency of the surfactant in the salt solution and confirmed the surface charge reversal by the polymer adsorption at pH = 4.0.
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23
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Wang L, Liu S, Wang T, Sun D. Effect of poly(oxypropylene)diamine adsorption on hydration and dispersion of montmorillonite particles in aqueous solution. Colloids Surf A Physicochem Eng Asp 2011. [DOI: 10.1016/j.colsurfa.2011.03.008] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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24
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Werzer O, Warr GG, Atkin R. Compact poly(ethylene oxide) structures adsorbed at the ethylammonium nitrate-silica interface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:3541-3549. [PMID: 21351777 DOI: 10.1021/la104577a] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The adsorption of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) onto silica from ethylammonium nitrate (a protic ionic liquid) has been investigated using colloid probe AFM force curve measurements. Steric repulsive forces were measured for PEO, confirming that PEO can compete with the ethylammonium cation and adsorb onto silica. The range of the repulsion increases with polymer molecular weight (e.g., from 1.4 nm for 0.01 wt % 10 kDa PEO to 40 nm for 0.01 wt % 300 kDa PEO) and with concentration (e.g., from 16 nm at 0.001 wt % to 78 nm at 0.4 wt % for 300 kDa PEO). Fits to the force curve data could not be obtained using standard models for a polymer brush, but excellent fits were obtained using the mushroom model, suggesting the adsorbed polymer films are compressed and relatively poorly solvated. No evidence for adsorption of 3.5 kDa PPO could be detected up to its solubility limit.
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Affiliation(s)
- Oliver Werzer
- Centre for Organic Electronics, The University of Newcastle, Callaghan, NSW 2308 Australia
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25
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Hierrezuelo J, Szilagyi I, Vaccaro A, Borkovec M. Probing Nanometer-Thick Polyelectrolyte Layers Adsorbed on Oppositely Charged Particles by Dynamic Light Scattering. Macromolecules 2010. [DOI: 10.1021/ma1014462] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- José Hierrezuelo
- Department of Inorganic, Analytical, and Applied Chemistry, University of Geneva, Sciences II, 30, Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland
| | - Istvan Szilagyi
- Department of Inorganic, Analytical, and Applied Chemistry, University of Geneva, Sciences II, 30, Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland
| | - Andrea Vaccaro
- Department of Inorganic, Analytical, and Applied Chemistry, University of Geneva, Sciences II, 30, Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland
| | - Michal Borkovec
- Department of Inorganic, Analytical, and Applied Chemistry, University of Geneva, Sciences II, 30, Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland
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26
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Vaccaro A, Hierrezuelo J, Skarba M, Galletto P, Kleimann J, Borkovec M. Structure of an adsorbed polyelectrolyte monolayer on oppositely charged colloidal particles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:4864-4867. [PMID: 19334686 DOI: 10.1021/la9007608] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
An adsorbed layer of a cationic polyelectrolyte, poly(diallyldimethyl-ammonium) chloride (PDADMAC) on negatively charged colloidal latex particles was investigated by small-angle neutron scattering (SANS) and dynamic light scattering (DLS). SANS gives a layer thickness of 8 +/- 1 A and a polymer volume fraction of 0.31 +/- 0.05 within the film. DLS gives a somewhat larger thickness of 18 +/- 2 A, and the discrepancy is likely due to the inhomogeneous nature of the layer and the existence of polymer tails or loops protruding into solution. These results show that a highly charged polyelectrolyte adsorbs on an oppositely charged colloidal particle in a flat configuration due to the attractive forces acting between the polyelectrolyte and the substrate.
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Affiliation(s)
- Andrea Vaccaro
- Department of Inorganic, Analytical, and Applied Chemistry, University of Geneva, 1211 Geneva 4, Switzerland
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27
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Balmer JA, Armes SP, Fowler PW, Tarnai T, Gáspár Z, Murray KA, Williams NSJ. Packing efficiency of small silica particles on large latex particles: a facile route to colloidal nanocomposites. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:5339-47. [PMID: 19260684 DOI: 10.1021/la8041555] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The adsorption of small silica particles onto large sterically stabilized poly(2-vinylpyridine) [P2VP] latex particles in aqueous solution is assessed as a potential route to nanocomposite particles with a "core-shell" morphology. Geometric considerations allow the packing efficiency, P, to be related to the number of adsorbed silica particles per latex particle, N. Making no assumptions about the packing structure, this approach leads to a theoretical estimate for P of 86 +/- 4%. Experimentally, dynamic light scattering is used to obtain a plot of hydrodynamic diameter against N, which indicates the conditions required for monolayer coverage of the latex by the silica particles. Transmission electron microscopy confirmed that, at approximately monolayer coverage, calcination of these nanocomposite particles led to the formation of well-defined hollow silica shells. This is interpreted as strong evidence for a contiguous monolayer of silica particles surrounding the latex cores. On this basis, an experimental value for P of 69 +/- 4% was estimated for nanocomposite particles prepared by the heteroflocculation of a 20 nm silica sol with near-monodisperse P2VP latexes of either 463 or 616 nm diameter at approximately pH 10. X-ray photoelectron spectroscopy was used to quantify the extent of latex surface coverage by the silica particles. This technique gave good agreement with the silica packing efficiencies estimated from calcination studies.
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Affiliation(s)
- Jennifer A Balmer
- Dainton Building, Department of Chemistry, The University of Sheffield, Sheffield, Brook Hill, S3 7HF United Kingdom
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Qiu D, Cosgrove T, Revell P, Howell I. Poly(ethylene oxide) Adsorption on Polystyrene Latex Particles in the Presence of Poly(styrenesulfonate sodium). Macromolecules 2008. [DOI: 10.1021/ma802237p] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Dong Qiu
- School of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, U.K., Port Sunlight Laboratory, Unilever Research, Quarry Road East, Bebington, The Wirral CH63 3JW, U.K., and School of Physical Sciences, University of Kent at Canterbury, Canterbury, Kent CT2 7NH, U.K
| | - Terence Cosgrove
- School of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, U.K., Port Sunlight Laboratory, Unilever Research, Quarry Road East, Bebington, The Wirral CH63 3JW, U.K., and School of Physical Sciences, University of Kent at Canterbury, Canterbury, Kent CT2 7NH, U.K
| | - Patricia Revell
- School of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, U.K., Port Sunlight Laboratory, Unilever Research, Quarry Road East, Bebington, The Wirral CH63 3JW, U.K., and School of Physical Sciences, University of Kent at Canterbury, Canterbury, Kent CT2 7NH, U.K
| | - Ian Howell
- School of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, U.K., Port Sunlight Laboratory, Unilever Research, Quarry Road East, Bebington, The Wirral CH63 3JW, U.K., and School of Physical Sciences, University of Kent at Canterbury, Canterbury, Kent CT2 7NH, U.K
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29
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Brotherson B, Bottomley LA, Ludovice P, Deng Y. Salt Effect on Cationic Polyacrylamide Conformation on Mica Studied by Single Molecule “Pulling” with Scanning Probe Microscopy. J Phys Chem B 2008; 112:12686-91. [DOI: 10.1021/jp805931b] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Brett Brotherson
- School of Chemical & Biomolecular Engineering and School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0620
| | - Lawrence A. Bottomley
- School of Chemical & Biomolecular Engineering and School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0620
| | - Peter Ludovice
- School of Chemical & Biomolecular Engineering and School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0620
| | - Yulin Deng
- School of Chemical & Biomolecular Engineering and School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0620
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30
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Flood C, Cosgrove T, Espidel Y, Welfare E, Howell I, Revell P. Fourier-transform Carr-Purcell-Meiboom-Gill NMR experiments on polymers in colloidal dispersions: how many polymer molecules per particle? LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:7875-7880. [PMID: 18588323 DOI: 10.1021/la800144c] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Fourier transform relaxation NMR has been used to study how the mobility of poly(ethylene oxide) is affected by its adsorption onto colloidal silica particles of various sizes. Novel results have been obtained which illustrate the unexploited potential of this method for the study of interfacial species in complex systems. The results quantify how polymer mobility varies along an adsorption isotherm. When the particles are in excess, the polymer is strongly adsorbed and hence has a large spin-spin magnetic relaxation rate constant, R(2). The value of R(2) in this region increases with particle size, because the associated reduction in particle surface curvature results in a reduction in the mobility of the adsorbed polymer. This is accompanied by a reduction in the signal intensity, as a higher fraction of the polymer is adsorbed in the form of train segments too immobile to detect using the Carr-Purcell-Meiboom-Gill pulse sequence. When the polymer concentration reaches approximately 0.5 mg m(-2), the initial region of high affinity adsorption ends and so the polymer solution concentration increases. This is accompanied by a reduction in R(2), which then approaches the value for a simple polymer solution in the absence of particles. The results are corroborated by comparison with rheological measurements and molecular dynamics simulations of an analogous particle-polymer system.
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Affiliation(s)
- Charlie Flood
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, United Kingdom.
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31
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Flood C, Cosgrove T, Espidel Y, Howell I, Revell P. Effects of surfactants and electrolytes on adsorbed layers and particle stability. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:7323-7328. [PMID: 18547088 DOI: 10.1021/la800143x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Adsorbed polymer and polyelectrolyte layers on colloidal silica nanoparticles have been studied in the presence of various salts and surfactants using photon correlation spectroscopy and solvent relaxation NMR. Poly(ethylene oxide) (PEO; molar mass 103.6 kg mol (-1)) adsorbed with a relatively high affinity and gave a layer thickness of 4.2 +/- 0.2 nm. While the nonionic surfactant used only increased this thickness slightly, anionic surfactants had a much greater effect, mainly due to repulsions between adsorbed aggregates, leading to expansion of the layer. A nonionic/anionic surfactant mixture was also tested and resulted in a larger increase in layer thickness than any of the individual surfactants. The dominant factor on addition of salt was generally the reduced solvency of PEO, which resulted in a further increase in the layer thickness but in some cases caused flocculation. This was not the case when the surfactant was sodium dodecylbenzenesulfonate; instead screening of the intermicellar repulsions possibly combined with surfactant-cation binding resulted in a reduction in the layer thickness. In comparison the affinity between silica and sodium polystyrenesulfonate was very weak. Anionic surfactants and salts did not noticeably increase the strength of adsorption, but instead encouraged flocculation. The situation was different with a nonionic surfactant, which was able to adsorb to silica itself and apparently facilitated a degree of polyelectrolyte adsorption as well.
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Affiliation(s)
- Charlie Flood
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, United Kingdom.
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32
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Olanya G, Iruthayaraj J, Poptoshev E, Makuska R, Vareikis A, Claesson PM. Adsorption characteristics of bottle-brush polymers on silica: effect of side chain and charge density. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:5341-5349. [PMID: 18422351 DOI: 10.1021/la703739v] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The adsorption behavior of bottle-brush polymers with different charge/PEO ratio on silica was studied using optical reflectometry and QCM-D. The results obtained under different solution conditions clearly demonstrate the existence of two distinct adsorption mechanisms depending on the ratio of charge/PEO. In the case of low-charge density brush polymers (0-10 mol %), the adsorption occurs predominantly through the PEO side chains. However, the presence of a small amount of charge along the backbone (as low as 2 mol %) increases the adsorption significantly above that of the uncharged bottle-brush polymer in pure water. As the charge density of the brush polymers is increased to 25 mol % or larger the adsorption occurs predominantly through electrostatic interactions. The adsorbed layer structure was studied by measuring the layer dissipation using QCM-D. The adsorbed layer formed by the uncharged brush polymer dissipates only a small amount of energy that indicates that the brush lie along the surface, the scenario in which the maximum number of PEO side chains interact with the surface. The adsorbed layers formed by the low-charge density brush polymers (2-10 mol %) in water are more extended, which results in large energy dissipation, whereas those formed by the high-charge density brush polymers (50-100 mol %) have their backbone relatively flat on the surface and the energy dissipation is again low.
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Affiliation(s)
- Geoffrey Olanya
- Department of Chemistry, Surface Chemistry, Royal Institute of Technology, SE-100 44 Stockholm, Sweden
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33
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Postmus BR, Leermakers FAM, Stuart MAC. Self-consistent field modeling of poly(ethylene oxide) adsorption onto silica: the multiple roles of electrolytes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:1930-1942. [PMID: 18205415 DOI: 10.1021/la7023154] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
In technological applications, it is increasingly important to understand and predict interfacial phenomena. Using a self-consistent field model within the Scheutjens-Fleer discretization scheme, we have developed a molecularly realistic model of the adsorption of poly(ethylene oxide) (PEO) onto silica from an aqueous solution. The bulk solution consists of water, PEO, 1:1 electrolyte, protons, and hydroxyl ions. The solvent quality is good below and becomes poor above a threshold ionic strength (of around 1 M). The silica surface features a number of silanol groups that have an affinity for PEO (by means of H bonding) when these groups are not dissociated. In line with experimental data, the surface changes from adsorbing to nonadsorbing at a sufficiently high pH. Even though PEO is uncharged, there is a complex effect of the ionic strength on the interfacial characteristics. For example, we report a non-monotonic behavior of the adsorbed amount as a function of ionic strength. Going from a low to a high ionic strength at a neutral or slightly basic pH, the adsorbed amount initially decreases as the surface affinity decreases (caused by the reduction of adsorption sites when, as a result of screening, the surface is increasingly charged) but then increases as a result of a reduction in solvent quality. These results indicate that molecularly realistic models can reveal much richer interfacial behavior than anticipated from generic models. The predictions follow many experimental findings.
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Affiliation(s)
- Bart R Postmus
- Laboratory of Physical Chemistry and Colloid Science, Wageningen University, Dreijenplein 6, 6703 HB Wageningen, The Netherlands.
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Flood C, Cosgrove T, Espidel Y, Howell I, Revell P. Sodium polyacrylate adsorption onto anionic and cationic silica in the presence of salts. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:6191-7. [PMID: 17439259 DOI: 10.1021/la070047z] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Sodium polyacrylate is well known for its application as a scale inhibitor in common household products, and the effects of both monovalent and divalent metal cations on its structure have been covered by a range of previous publications. In the present article, we extend this work by using solvent relaxation NMR to look at the adsorption of the polyelectrolyte onto both positively and negatively charged silica and how this is altered by calcium chloride. In the anionic case, we found that polyacrylate adsorption was predictably very weak, and interestingly, perhaps counterintuitively, it was further reduced by calcium ions. This is probably linked to NaPA-Ca2+ binding, which changes the conformation and charge of the polyelectrolyte. In contrast, NaPA adsorbs very strongly on cationic silica, to the point that precipitation often occurs, particularly on addition of salt.
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Affiliation(s)
- Charlie Flood
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK
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Gillies G, Lin W, Borkovec M. Charging and Aggregation of Positively Charged Latex Particles in the Presence of Anionic Polyelectrolytes. J Phys Chem B 2007; 111:8626-33. [PMID: 17465535 DOI: 10.1021/jp069009z] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Charging behavior and colloidal stability of amidine latex particles are studied in the presence of poly(sodium styrene sulfonate) (PSS) and KCl. Detailed measurements of electrophoretic mobility, adsorbed layer thickness, and aggregation (or coagulation) rate constant on varying the polymer dose, molecular mass of the polymer, and ionic strength are reported. Polyelectrolyte adsorption leads to the characteristic charge reversal (or overcharging) of the colloidal particles at the isoelectric point (IEP). In accordance with classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, uncharged particles tend to aggregate because of van der Waals attraction, whereas charged particles are stabilized by electrical double layer repulsion. Attractive patch-charge interactions originating from the laterally inhomogeneous structure of the adsorbed polymer substantially decrease the suspension stability or even accelerate the aggregation rate beyond diffusion control. These electrostatic non-DLVO forces become progressively important with increasing molecular mass of the polymer and the ionic strength of the solution. At higher polymer dose of typically 10 times the IEP, one observes the formation of a saturated layer of the adsorbed polymer with a thickness of several nanometers. Its thickness increases with increasing molecular mass, whereby the layer becomes increasingly porous. This layer does not seem to be involved in the suspension stabilization, since at such high polymer doses the double layer repulsion has attained sufficient strength to stabilize the suspension.
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Affiliation(s)
- Graeme Gillies
- Laboratory of Colloid and Surface Chemistry, Department of Inorganic, Analytical, and Applied Chemistry, University of Geneva, Sciences II, 30 Quai Ernest Ansermet, 1211 Geneva 4, Switzerland
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36
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Flood C, Cosgrove T, Qiu D, Espidel Y, Howell I, Revell P. Influence of a surfactant and electrolytes on adsorbed polymer layers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:2408-13. [PMID: 17309202 DOI: 10.1021/la062034b] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Solvent relaxation NMR and small-angle neutron scattering have been used to characterize adsorbed poly(ethylene oxide) (PEO) layers on silica at a range of surfactant and electrolyte concentrations. Below the critical aggregation concentration (cac), the results suggest that sodium dodecyl sulfate (SDS) interacts relatively weakly, perhaps analogously to a simple salt reducing the solvency of PEO. This is evidenced by a decrease in the adsorbed layer thickness combined with an increase in the bound fraction, although the total adsorbed amount is not greatly affected. The layer thickness goes through a minimum at the cac, after which further SDS addition results in the formation of PEO/SDS aggregates that repel each other and, hence, tend to desorb. The adsorbed amount therefore decreases, from 0.7 mg m(-2) initially to 0.2 mg m(-2) with 32 mM SDS. The aggregates that remain adsorbed also repel, and hence, there is an increase in the layer thickness and the persistence length, while the bound fraction is reduced. In comparison, the effects of electrolyte at the ionic strength studied are relatively minimal. There is, however, evidence that the repulsions between adsorbed PEO/SDS aggregates are partially screened, allowing them to approach each other more readily. This leads to a contraction of the adsorbed layer when the SDS concentration is sufficiently high.
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Affiliation(s)
- Charlie Flood
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, U.K.
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Carrot G, Harrak AE, Oberdisse J, Jestin J, Boué F. Polymer grafting from 10-nm individual particles: proving control by neutron scattering. SOFT MATTER 2006; 2:1043-1047. [PMID: 32680206 DOI: 10.1039/b600749j] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The core-shell structure of nanoparticles (5 nm radius) of silica grafted with polymer growing from the particle ("grafting from") is characterized by small angle neutron scattering (SANS), to our knowledge for the first time. This is made possible by a good control of the colloidal dispersion at each step of the synthesis. With this aim, we have improved our chemical procedure based on atom transfer radical polymerization (ATRP), which allows a good control of kinetics and polydispersity: the reaction takes place in a polar solvent, and the reaction medium remains always crystal clear. For such small particles, in contrary to direct space imaging, SANS is appropriate for characterization of the polymer corona as well as of the silica core using contrast matching provided by mixing normal and deuterated solvent. This allows checking of the level of aggregation at the nanoscale, which is found to be limited to a few percent of the particles in the reaction batch. After an initial slight increase, it is reduced by further polymerization, while the polymer layer grows progressively. After purification, grafted silica can be characterized accurately: its scattering can be fitted by a model of a silica core containing three to five particles surrounded by a polymer shell of thickness 7 nm. This is in good agreement with chain length and grafting density (214 sites per particle) evaluated by chemical analysis; hence SANS provides quantitative insight on chemical synthesis.
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Affiliation(s)
- G Carrot
- Laboratoire Léon Brillouin, CNRS-CEA, CE SACLAY, 91191, Gif-sur-Yvette Cedex, France
| | - A El Harrak
- Laboratoire Léon Brillouin, CNRS-CEA, CE SACLAY, 91191, Gif-sur-Yvette Cedex, France
| | - J Oberdisse
- Laboratoire Léon Brillouin, CNRS-CEA, CE SACLAY, 91191, Gif-sur-Yvette Cedex, France and Laboratoire des Colloïdes, des Verres et des Nanomatériaux, Université de Montpellier II, 34095, Montpellier Cedex 05, France
| | - J Jestin
- Laboratoire Léon Brillouin, CNRS-CEA, CE SACLAY, 91191, Gif-sur-Yvette Cedex, France
| | - F Boué
- Laboratoire Léon Brillouin, CNRS-CEA, CE SACLAY, 91191, Gif-sur-Yvette Cedex, France
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