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Study on the Mechanism of the Reversible Color Change of Polyacrylic Acid Modified Gold Nanoparticles Responding to pH. MATERIALS 2021; 14:ma14133679. [PMID: 34279250 PMCID: PMC8269886 DOI: 10.3390/ma14133679] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Revised: 06/06/2021] [Accepted: 06/24/2021] [Indexed: 11/29/2022]
Abstract
In view of various explanations regarding the pH response of the nanocomposite of gold nanoparticles (AuNPs) modified with polyacrylic acid (PAA) molecules in reported literature, in this work, AuNPs with a size of 20 nm saturatedly loaded with PAA molecules (AuNPs-PAAs) were used to investigate the following aspects of this issue. We investigated the effects of pH on the stability of AuNPs-PAAs in the presence of salt, CTAB, poly (sodium styrenesulfonate) (PSS), ethanol, and free PAA, respectively. Common techniques were undertaken to evaluate the stability, including UV-Vis spectroscopy, Zeta potential analysis, and TEM. The results show that AuNPs-PAAs could respond to pH variations, having a reversible aggregation-to-disaggregation, accompanying their Zeta potential change. The proposed corresponding mechanism was that this reversible change was attributes to the net charge variation of AuNPs-PAAs induced by a reversible protonation-to-deprotonation of PAA rather than the conformational change. It was found that salt, CTAB, PSS, and free PAA could strengthen the dispersity of AuNPs-PAAs, even though their absolute Zeta potential values were decreased to small values or dropped to nearly zero. This abnormal phenomenon was explained by solvation. It was also found that AuNPs-PAAs have an opposite pH response in aqueous and ethanol solutions, justifying the solvation effect. All these results revealed the conformational stability of PAAs immobilized on AuNPs. The methods and the findings of this investigation give some new insights to understand the pH-response of AuNPs-PAAs composites and the design of AuNPs-PAAs-based functional sensors.
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2
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Liao Z, Wu G, Lee D, Yang S. Ultrastable Underwater Anti-Oil Fouling Coatings from Spray Assemblies of Polyelectrolyte Grafted Silica Nanochains. ACS APPLIED MATERIALS & INTERFACES 2019; 11:13642-13651. [PMID: 30920799 DOI: 10.1021/acsami.8b19310] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Surfaces that have superhydrophilic characteristics are known to exhibit extreme oil repellency under water, which is attractive for applications including anti-fogging, water-oil separations, and self-cleaning. However, superhydrophilic surfaces can also be easily fouled and lose their extreme oil repellency, which limits their usage in practical applications. In this work, we create an anti-oil fouling coating by spray coating poly(acrylic acid) (PAA)-grafted SiO2 nanochains (approximately 45 nm wide and 300 nm long) onto solid surfaces, forming a nanoporous film exhibiting superhydrophilicity (water contact angle in air ≈ 0°) and underwater superoleophobicity (dichloroethane contact angle ≥ 165°). The polymer-grafted nanochain assemblies exhibit extremely low contact angle hysteresis (<1°) and small adhesion hysteresis (-0.05 mN m-1), and thus, oil can readily roll off from the surface when the coating is immersed in water. Compared to other superhydrophilic surfaces, we show that both the unique structure of spray-assembled nanochains and the hygroscopic nature of PAA are essential to enable ultrastable anti-oil fouling. Even after the PAA-grafted nanochain coating is purposely fouled by oil, oil can be readily and completely expelled and lifted-off from the coating within 10 s when placed under water. Further, we show that our coating retains underwater superoleophobicity even after being subjected to shearing under water for more than 168 h. Our approach offers a simple yet versatile method to create an ultrastable superhydrophilic and anti-oil fouling coating via a scalable manufacturing method.
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Affiliation(s)
- Zhiwei Liao
- Department of Chemical and Biomolecular Engineering , University of Pennsylvania , 220 South 33rd Street , Philadelphia , Pennsylvania 19104 , United States
| | - Gaoxiang Wu
- Department of Materials Science and Engineering , University of Pennsylvania , 3231 Walnut Street , Philadelphia , Pennsylvania 19104 , United States
| | - Daeyeon Lee
- Department of Chemical and Biomolecular Engineering , University of Pennsylvania , 220 South 33rd Street , Philadelphia , Pennsylvania 19104 , United States
| | - Shu Yang
- Department of Materials Science and Engineering , University of Pennsylvania , 3231 Walnut Street , Philadelphia , Pennsylvania 19104 , United States
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Lhermerout R, Davitt K. Contact angle dynamics on pseudo-brushes: Effects of polymer chain length and wetting liquid. Colloids Surf A Physicochem Eng Asp 2019. [DOI: 10.1016/j.colsurfa.2019.01.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Shiomoto S, Yamaguchi K, Kobayashi M. Time Evolution of Precursor Thin Film of Water on Polyelectrolyte Brush. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:10276-10286. [PMID: 30102545 DOI: 10.1021/acs.langmuir.8b02070] [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 microscopic wetting behavior of a water film on the line-patterned surface of a polyelectrolyte brush was directly visualized using an optical microscope by dyeing procedures. Surface line patterns of 5 and 5 μm width or 10 and 5 μm width for the polyelectrolyte brush and hydrophobic monolayer, respectively, were prepared by a photolithography process, chemical vapor adsorption method, and surface-initiated polymerization. A droplet of water containing dye was placed on the line-patterned surface. In front of the contact line, a water film with a nanometer-scale thickness, referred to as a precursor film, elongated along the polymer brush line with time. The elongation velocity at the first stage increased as the brush line width increased. On the other hand, at the second stage after the macroscopic contact line stopped moving, the precursor film continued to elongate in proportion to the 0.6 power of time, independent of the brush thickness, line width, and droplet volume.
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Guennouni Z, Goldmann M, Fauré MC, Fontaine P, Perrin P, Limagne D, Cousin F. Coupled Effects of Spreading Solvent Molecules and Electrostatic Repulsions on the Behavior of PS-b-PAA Monolayers at the Air-Water Interface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:12525-12534. [PMID: 28972777 DOI: 10.1021/acs.langmuir.7b02664] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We describe the surface behavior of PS-b-PAA monolayers at the air/water interface using N,N-dimethyformamide (DMF) as spreading solvent. At low pH, when the PAA blocks are neutral, the surface pressure versus molecular area isotherm shows a pseudoplateau associated with the presence of remaining spreading solvent molecules in the monolayer, as we described in a former study (Guennouni et al., Langmuir, 2016). We show here that the width of the plateau decreases when increasing pH up to its complete disappearance at high pH, when PAA blocks are fully charged, although two regimes of compressibilities on the isotherm still exist. A refined structural study at pH 9 combining specular neutron reflectivity (SNR), grazing-incidence small-angle X-ray scattering (GISAXS), and atomic force microscopy (AFM) in liquid measurements shows that (i) PAA blocks are stretched in solution, as expected from polyelectrolyte brushes in the osmotic regime; (ii) the system undergoes a spinodal decomposition during deposit at the air/water interface in the presence of DMF. Upon compression, the Qxy* position of the peak associated with the spinodal structure remains almost constant but its intensity evolves strongly and passes through a maximum at intermediate pressures. This reveals two operating processes in the system: strong electrostatic repulsions between chains that prevent in-plane reorganizations and force such reorganizations to occur from the surface to the volume and progressive expulsion of the DMF molecules from the monolayer. These processes have antagonist effects on the intensity of the peak: the increase of the repulsions makes it more pronounced, whereas the expulsion of solvent makes it vanish due to the loss of contrast.
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Affiliation(s)
- Zineb Guennouni
- Sorbonne Universités, UPMC Univ Paris 06, CNRS-UMR 7588, Institut des NanoSciences de Paris, 4 place Jussieu, F-75005 Paris, France
- Laboratoire Léon Brillouin, CEA Saclay , 91191 Gif sur Yvette Cedex, France
| | - Michel Goldmann
- Sorbonne Universités, UPMC Univ Paris 06, CNRS-UMR 7588, Institut des NanoSciences de Paris, 4 place Jussieu, F-75005 Paris, France
- Faculté des Sciences Fondamentales et Biomédicales, Université Paris Descartes , 45 rue des Saints Pères, 75006 Paris, France
- Synchrotron SOLEIL , L'Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette, France
| | - Marie-Claude Fauré
- Sorbonne Universités, UPMC Univ Paris 06, CNRS-UMR 7588, Institut des NanoSciences de Paris, 4 place Jussieu, F-75005 Paris, France
- Faculté des Sciences Fondamentales et Biomédicales, Université Paris Descartes , 45 rue des Saints Pères, 75006 Paris, France
| | - Philippe Fontaine
- Synchrotron SOLEIL , L'Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette, France
| | - Patrick Perrin
- Ecole Supérieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI), ParisTech, PSL Research University, Sciences et Ingénierie de la Matière Molle (SIMM), CNRS UMR 7615, 10, Rue Vauquelin, F-75231 Cedex 05 Paris, France
- Sorbonne-Universités, UPMC Univ Paris 06, SIMM, 10, Rue Vauquelin, F-75231 Cedex 05 Paris, France
| | - Denis Limagne
- Sorbonne Universités, UPMC Univ Paris 06, CNRS-UMR 7588, Institut des NanoSciences de Paris, 4 place Jussieu, F-75005 Paris, France
| | - Fabrice Cousin
- Laboratoire Léon Brillouin, CEA Saclay , 91191 Gif sur Yvette Cedex, France
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Foroutan M, Zahedi H, Esmaeilian F. Temperature effects on spreading of water nano-droplet on poly(methyl methacrylate): A molecular dynamics simulation study. ACTA ACUST UNITED AC 2017. [DOI: 10.1002/polb.24409] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
- Masumeh Foroutan
- Department of Physical Chemistry, School of Chemistry, College of Science; University of Tehran; Tehran 1417614418 Iran
| | - Hojat Zahedi
- Department of Physical Chemistry, School of Chemistry, College of Science; University of Tehran; Tehran 1417614418 Iran
| | - Farshad Esmaeilian
- Department of Physical Chemistry, School of Chemistry, College of Science; University of Tehran; Tehran 1417614418 Iran
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Murakami D, Kobayashi M, Higaki Y, Jinnai H, Takahara A. Swollen structure and electrostatic interactions of polyelectrolyte brush in aqueous solution. POLYMER 2016. [DOI: 10.1016/j.polymer.2016.04.041] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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8
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Guennouni Z, Cousin F, Fauré MC, Perrin P, Limagne D, Konovalov O, Goldmann M. Self-Organization of Polystyrene-b-polyacrylic Acid (PS-b-PAA) Monolayer at the Air/Water Interface: A Process Driven by the Release of the Solvent Spreading. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:1971-1980. [PMID: 26824719 DOI: 10.1021/acs.langmuir.5b02652] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We present an in situ structural study of the surface behavior of PS-b-PAA monolayers at the air/water interface at pH 2, for which the PAA blocks are neutral and using N,N-dimethyformamide (DMF) as spreading solvent. The surface pressure versus molecular area isotherm shows a perfectly reversible pseudoplateau over several cycles of compression/decompression. The width of such plateau enlarges when increasing temperature, conversely to what is classically observed in the case of an in-plane first order transition. We combined specular neutron reflectivity (SNR) experiments with contrast variation to solve the profile of each block perpendicular to the surface with grazing-incidence small-angle scattering (GISAXS) measurements to determine the in-plane structure of the layer. SNR experiments showed that both PS and PAA blocks remain adsorbed on the surface for all surface pressure probed. A correlation peak at Q(xy)* = 0.021 Å(-1) is evidenced by GISAXS at very low surface pressure which intensity first increases on the plateau. When compressing further, its intensity decays while Q(xy)* is shifted toward low Q(xy). The peak fully disappears at the end of the plateau. These results are interpreted by the formation of surface aggregates induced by DMF molecules at the surface. These DMF molecules remain adsorbed within the PS core of the aggregates. Upon compression, they are progressively expelled from the monolayer, which gives rise to the pseudoplateau on the isotherm. The intensity of the GISAXS correlation peak is set by the amount of DMF within the monolayer as it vanishes when all DMF molecules are expelled. This result emphizes the role of the solvent in Langmuir monolayer formed by amphiphilic copolymers which hydrophobic and hydrophilic parts are composed by long polymer chains.
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Affiliation(s)
- Zineb Guennouni
- Sorbonne Universités, UPMC Univ Paris 06, CNRS-UMR 7588, Institut des NanoSciences de Paris, 4 place Jussieu F-75005 Paris, France
- Laboratoire Léon Brillouin, CEA Saclay, 91191 Gif sur Yvette Cedex, France
| | - Fabrice Cousin
- Laboratoire Léon Brillouin, CEA Saclay, 91191 Gif sur Yvette Cedex, France
| | - Marie-Claude Fauré
- Sorbonne Universités, UPMC Univ Paris 06, CNRS-UMR 7588, Institut des NanoSciences de Paris, 4 place Jussieu F-75005 Paris, France
- Faculté des Sciences Fondamentales et Biomédicales, Université Paris Descartes , 45 rue des Saints Pères , 75006 Paris, France
| | - Patrick Perrin
- Ecole Supérieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI), ParisTech, PSL Research University, Sciences et Ingénierie de la Matière Molle (SIMM), CNRS UMR 7615, 10, Rue Vauquelin, F-75231 Cedex 05 Paris, France
- Sorbonne-Universités, UPMC Univ Paris 06, SIMM, 10, Rue Vauquelin, F-75231 Cedex 05 Paris, France
| | - Denis Limagne
- Sorbonne Universités, UPMC Univ Paris 06, CNRS-UMR 7588, Institut des NanoSciences de Paris, 4 place Jussieu F-75005 Paris, France
| | - Oleg Konovalov
- European Synchrotron Radiation Facility , 6 rue Jules Horowitz 38000 Grenoble, France
| | - Michel Goldmann
- Sorbonne Universités, UPMC Univ Paris 06, CNRS-UMR 7588, Institut des NanoSciences de Paris, 4 place Jussieu F-75005 Paris, France
- Faculté des Sciences Fondamentales et Biomédicales, Université Paris Descartes , 45 rue des Saints Pères , 75006 Paris, France
- Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, BP 48, 91192 Gif-sur-Yvette, France
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Higaki Y, Kobayashi M, Murakami D, Takahara A. Anti-fouling behavior of polymer brush immobilized surfaces. Polym J 2016. [DOI: 10.1038/pj.2015.137] [Citation(s) in RCA: 102] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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10
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Murakami D, Kobayashi M, Moriwaki T, Ikemoto Y, Jinnai H, Takahara A. Spreading and structuring of water on superhydrophilic polyelectrolyte brush surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:1148-1151. [PMID: 23281847 DOI: 10.1021/la304697q] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The wetting behavior of superhydrophilic polyelectrolyte brushes was investigated. Reflection interference contrast microscopy demonstrated that the contact angles of water on the polyelectrolyte brushes were extremely low but remained finite in the range of <3°. The presence of water molecules was evident, even outside the macroscopic water droplet. These water molecules were confined to the thin brush layers and contained a highly ordered hydrogen bond network, which was identified as structural water. The presence of the thin film and the structural water changed the surface energies, which prevented the complete wetting of the surface.
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Affiliation(s)
- Daiki Murakami
- Japan Science and Technology Agency (JST), ERATO, Takahara Soft Interfaces Project, CE80, Kyushu University, 744 Motooka, Fukuoka 819-0395, Japan
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11
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Kobayashi M, Terayama Y, Yamaguchi H, Terada M, Murakami D, Ishihara K, Takahara A. Wettability and antifouling behavior on the surfaces of superhydrophilic polymer brushes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:7212-7222. [PMID: 22500465 DOI: 10.1021/la301033h] [Citation(s) in RCA: 266] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The surface wettabilities of polymer brushes with hydrophobic and hydrophilic functional groups were discussed on the basis of conventional static and dynamic contact angle measurements of water and hexadecane in air and captive bubble measurements in water. Various types of high-density polymer brushes with nonionic and ionic functional groups were prepared on a silicon wafer by surface-initiated atom-transfer radical polymerization. The surface free energies of the brushes were estimated by Owens-Wendt equation using the contact angles of various probe liquids with different polarities. The decrease in the water contact angle corresponded to the polarity of fluoroalkyl, hydroxy, ethylene oxide, amino, carboxylic acid, ammonium salt, sulfonate, carboxybetaine, sulfobetaine, and phosphobetaine functional groups. The poly(2-perfluorooctylethyl acrylate) brush had a low surface free energy of approximately 8.7 mN/m, but the polyelectrolyte brushes revealed much higher surface free energies of 70-74 mN/m, close to the value for water. Polyelectrolyte brushes repelled both air bubbles and hexadecane in water. Even when the silicone oil was spread on the polyelectrolyte brush surfaces in air, once they were immersed in water, the oil quickly rolled up and detached from the brush surface. The oil detachment behavior observed on the superhydrophilic polyelectrolyte brush in water was explained by the low adhesion force between the brush and the oil, which could contribute to its excellent antifouling and self-cleaning properties.
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Affiliation(s)
- Motoyasu Kobayashi
- Japan Science Technology Agency, ERATO, Takahara Soft Interfaces Project.
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12
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Influence of alkyl chain length and molecular weight on the surface functionalization via adsorption/entrapment with biocidal cationic block copolymers. Eur Polym J 2011. [DOI: 10.1016/j.eurpolymj.2011.09.019] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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13
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Adsorption of modified dextrins to a hydrophobic surface: QCM-D studies, AFM imaging, and dynamic contact angle measurements. J Colloid Interface Sci 2010; 345:417-26. [DOI: 10.1016/j.jcis.2010.01.075] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2009] [Revised: 01/19/2010] [Accepted: 01/23/2010] [Indexed: 11/18/2022]
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Muñoz-Bonilla A, van Herk AM, Heuts JPA. Preparation of Hairy Particles and Antifouling Films Using Brush-Type Amphiphilic Block Copolymer Surfactants in Emulsion Polymerization. Macromolecules 2010. [DOI: 10.1021/ma9027257] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Alexandra Muñoz-Bonilla
- Laboratory of Polymer Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
- Instituto de Ciencia y Tecnología de Polímeros (CSIC), C/Juan de la Cierva 3, 28006 Madrid, Spain
| | - Alex M. van Herk
- Laboratory of Polymer Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
| | - Johan P. A. Heuts
- Laboratory of Polymer Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
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Beaussart A, Parkinson L, Mierczynska-Vasilev A, Ralston J, Beattie DA. Effect of adsorbed polymers on bubble--particle attachment. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:13290-13294. [PMID: 19860372 DOI: 10.1021/la903145h] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The influence of adsorbed dextrin-based polymers on the attachment of a rising air bubble to a talc surface has been investigated. Liquid film rupture and dynamic contact angle studies have highlighted the major role that adsorbed polymers can play in bubble-particle attachment. No direct link was established between the equilibrium contact angle of polymer-treated talc surfaces and talc flotation recovery. However, clear correlations were observed between the flotation recovery of polymer-treated talc and the measured wetting film rupture time and rate of dewetting for a bubble attaching to a talc basal plane surface treated with the polymers. The retardation of the three-phase contact line expansion caused by the adsorbed polymers was found to have the largest influence on the bubble-particle attachment. The effect of the morphology (coverage, distribution, and shape) of the adsorbed layer on the wetting film rupture and the motion of the receding water front is discussed.
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Affiliation(s)
- Audrey Beaussart
- Ian Wark Research Institute, ARC Special Research Centre for Particles and Material Interfaces, University of South Australia, Mawson Lakes, SA 5095, Australia
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Theodoly O, Jacquin M, Muller P, Chhun S. Adsorption kinetics of amphiphilic diblock copolymers: from kinetically frozen colloids to macrosurfactants. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:781-793. [PMID: 19177645 DOI: 10.1021/la8030254] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We investigated the spontaneous adsorption properties of charged amphiphilic diblock copolymers on hydrophobic surfaces and explained the transition of behavior from depleting frozen colloids (that do not adsorb at all) to fast adsorbing macrosurfactants when the hydrophobicity of the nonsoluble block is reduced. Three copolymer families have been used with the same hydrophilic block poly(acrylic acid), a weak acid whose ionization alpha can be varied by changing the pH. The hydrophobic blocks polystyrene, PS, poly(n-butyl acrylate), PBA, and poly(diethylene glycol ethyl ether acrylate), PDEGA, have interfacial tensions with water gammacore/solvent, respectively, of 32, 20, and 3 mN/m. We were mainly interested in the regime of high ionization alpha > 0.3, where PAA chains have no affinity for hydrophobic surfaces, and we verified experimentally that micelles do not adsorb directly. With the three copolymer families we show that the adsorption kinetics at an early stage is driven by the self-assembly properties in bulk solution: adsorption is hampered for PS-b-PAA (physically/kinetically frozen micelles in solution), controlled by unimer extraction for PBA-b-PAA (nonequilibrium micelles in solution with very low CMC < 10-4 wt %), and controlled by unimer diffusion and electrostatic repulsion for PDEGA-b-PAA (micelles at equilibrium in solution with high CMC is approximately 1-5 wt %). This explains the power law dependences of adsorption with concentration as C-1 for PBA-b-PAA and C-2 for PDEGA-b-PAA. It is finally the interfacial tension with water of the nonsoluble block and not its glass transition that is the main control of bulk solution self-assembly and consequently of the adsorption kinetics properties of amphiphilic diblocks. We also proved by preparative GPC that the fraction of non-self-assembling diblock chains, which exists in all highly hydrophobic amphiphilic diblock systems, plays a negligible role in the adsorption properties. Finally, we investigated the intrinsic thermodynamic affinity between amphiphilic diblocks and hydrophobic surfaces. We show quantitatively that this affinity depends dominantly on the interfacial energies between the hydrophobic block, the surface, and water: diblocks with strongly hydrophobic nonsoluble blocks (PS, PBA) have a low affinity for weakly hydrophobic surfaces, and oppositely, diblocks with weakly hydrophobic nonsoluble block (PDEGA) have a universal affinity for hydrophobic surfaces (like small-molecule surfactants but for different physical reasons). Finally, we showed via surface rheology that when adsorption occurs anchoring is strong and irreversible for very hydrophobic diblocks (PBA-b-PAA) and weaker and (partially) reversible for less hydrophobic diblocks (PDEGA-b-PAA).
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Affiliation(s)
- O Theodoly
- Complex Fluids Laboratory, CNRS FRE 3084, France.
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