1
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Liu B, Grest GS, Cheng S. Inducing stratification of colloidal mixtures with a mixed binary solvent. SOFT MATTER 2023; 19:9195-9205. [PMID: 37997155 DOI: 10.1039/d3sm01192e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2023]
Abstract
Molecular dynamics simulations are used to demonstrate that a binary solvent can be used to stratify colloidal mixtures when the suspension is rapidly dried. The solvent consists of two components, one more volatile than the other. When evaporated at high rates, the more volatile component becomes depleted near the evaporation front and develops a negative concentration gradient from the bulk of the mixture to the liquid-vapor interface while the less volatile solvent is enriched in the same region and exhibit a positive concentration gradient. Such gradients can be used to drive a binary mixture of colloidal particles to stratify if one is preferentially attracted to the more volatile solvent and the other to the less volatile solvent. During solvent evaporation, the fraction of colloidal particles preferentially attracted to the less volatile solvent is enhanced at the evaporation front, whereas the colloidal particles having stronger attractions with the more volatile solvent are driven away from the interfacial region. As a result, the colloidal particles show a stratified distribution after drying, even if the two colloids have the same size.
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Affiliation(s)
- Binghan Liu
- Department of Physics, Center for Soft Matter and Biological Physics, and Macromolecules Innovation Institute, Virginia Tech, Blacksburg, Virginia 24061, USA.
| | - Gary S Grest
- Sandia National Laboratories, Albuquerque, NM 87185, USA
| | - Shengfeng Cheng
- Department of Physics, Center for Soft Matter and Biological Physics, and Macromolecules Innovation Institute, Virginia Tech, Blacksburg, Virginia 24061, USA.
- Department of Mechanical Engineering, Virginia Tech, Blacksburg, Virginia 24061, USA
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2
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Hooiveld E, Dols M, van der Gucht J, Sprakel J, van der Kooij HM. Quantitative imaging methods for heterogeneous multi-component films. SOFT MATTER 2023; 19:8871-8881. [PMID: 37955195 PMCID: PMC10663990 DOI: 10.1039/d3sm01212c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Accepted: 11/02/2023] [Indexed: 11/14/2023]
Abstract
The drying of multi-component dispersions is a common phenomenon in a variety of everyday applications, including coatings, inks, processed foods, and cosmetics. As the solvent evaporates, the different components may spontaneously segregate laterally and/or in depth, which can significantly impact the macroscopic properties of the dried film. To obtain a quantitative understanding of these processes, high-resolution analysis of segregation patterns is crucial. Yet, current state-of-the-art methods are limited to transparent, non-deformable labeled colloids, limiting their applicability. In this study, we employ three techniques that do not require customized samples, as their imaging contrast relies on intrinsic variations in the chemical nature of the constituent species: confocal Raman microscopy, cross-sectional Raman microscopy, and a combination of scanning electron microscopy and energy dispersive X-ray analysis (SEM-EDX). For broad accessibility, we offer a thorough guide to our experimental steps and data analysis methods. We benchmark the capabilities on a film that dries homogeneously at room temperature but exhibits distinct segregation features at elevated temperature, notably self-stratification, i.e., autonomous layer formation, due to a colloidal size mismatch. Confocal Raman microscopy offers a direct means to visualize structures in three dimensions without pre-treatment, its accuracy diminishes deeper within the film, making cross-sectional Raman imaging and SEM-EDX better options. The latter is the most elaborate method, yet we show that it can reveal the most subtle and small-scale microseparation of the two components in the lateral direction. This comparative study assists researchers in choosing and applying the most suitable technique to quantify structure formation in dried multi-component films.
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Affiliation(s)
- Ellard Hooiveld
- Physical Chemistry and Soft Matter, Wageningen University & Research, Stippeneng 4, 6708 WE Wageningen, The Netherlands.
| | - Maarten Dols
- Physical Chemistry and Soft Matter, Wageningen University & Research, Stippeneng 4, 6708 WE Wageningen, The Netherlands.
| | - Jasper van der Gucht
- Physical Chemistry and Soft Matter, Wageningen University & Research, Stippeneng 4, 6708 WE Wageningen, The Netherlands.
| | - Joris Sprakel
- Laboratory of Biochemistry, Wageningen University & Research, Stippeneng 4, 6708 WE Wageningen, The Netherlands
| | - Hanne M van der Kooij
- Physical Chemistry and Soft Matter, Wageningen University & Research, Stippeneng 4, 6708 WE Wageningen, The Netherlands.
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3
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Zika A, Agarwal M, Schweins R, Gröhn F. Joining Two Switches in One Nano-Object: Photoacidity and Photoisomerization in Electrostatic Self-Assembly. Chemistry 2023; 29:e202203373. [PMID: 36336659 DOI: 10.1002/chem.202203373] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Accepted: 11/02/2022] [Indexed: 11/09/2022]
Abstract
Multi-switchable supramolecular nano-objects that respond to irradiation of different wavelengths with changes in size and shape have been built from two different water-soluble molecular switches, joined by attachment to the same polyelectrolyte. Accordingly, two wavelength-specific reactions, namely the excited-state proton dissociation of a photoacid and the cis-trans isomerization of an azo dye, are combined in one supramolecular nano-object that is stable in aqueous solution. The concept has potential in the fields of sensors, molecular motors, and transport.
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Affiliation(s)
- Alexander Zika
- Department of Chemistry and Pharmacy &, Interdisciplinary Center for Molecular Materials, Friedrich-Alexander Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058, Erlangen, Germany
| | - Mohit Agarwal
- Department of Chemistry and Pharmacy &, Interdisciplinary Center for Molecular Materials, Friedrich-Alexander Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058, Erlangen, Germany.,DS / LSS, Institut Laue-Langevin, 71 Avenue des Martyrs, CS 20 156, 38042, Grenoble Cedex 9, France
| | - Ralf Schweins
- DS / LSS, Institut Laue-Langevin, 71 Avenue des Martyrs, CS 20 156, 38042, Grenoble Cedex 9, France
| | - Franziska Gröhn
- Department of Chemistry and Pharmacy &, Interdisciplinary Center for Molecular Materials, Friedrich-Alexander Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058, Erlangen, Germany
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4
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Palmer TR, van der Kooij HM, Abu Bakar R, McAleese CD, Duewel M, Greiner K, Couture P, Sharpe MK, Keddie JL. Diffusiophoresis-Driven Stratification in Pressure-Sensitive Adhesive Films from Bimodal Waterborne Colloids. ACS APPLIED POLYMER MATERIALS 2023; 5:1565-1576. [PMID: 36817335 PMCID: PMC9926484 DOI: 10.1021/acsapm.2c02044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/25/2022] [Accepted: 01/11/2023] [Indexed: 06/18/2023]
Abstract
The uses of pressure-sensitive adhesives (PSAs) are wide ranging, with applications including labels, tapes, and graphics. To achieve good adhesion, a PSA must exhibit a balance of viscous and elastic properties. Previous research has found that a thin, elastic surface layer on top of a softer, dissipative layer resulted in greater tack adhesion compared with the single layers. Superior properties were achieved through a bilayer obtained via successive depositions, which consume energy and time. To achieve a multilayered structure via a single deposition process, we have stratified mixtures of waterborne colloidal polymer particles with two different sizes: large poly(acrylate) adhesive particles (ca. 660 nm in diameter) and small poly(butyl acrylate) (pBA) particles (ca. 100 nm). We used two types of pBA within the particles: either viscoelastic pBA without an added cross-linker or elastic pBA with a fully cross-linked network. Stratified surface layers of deuterium-labeled pBA particles with thicknesses of at least 1 μm were found via elastic recoil detection and qualitatively verified via the analysis of surface topography. The extent of stratification increased with the evaporation rate; films that were dried slowest exhibited no stratification. This result is consistent with a model of diffusiophoresis. When the elastic, cross-linked pBA particles were stratified at the surface, the tack adhesion properties made a transition from brittle failure to tacky. For pBA without an added cross-linker, all adhesives showed fibrillation during debonding, but the extent of fibrillation increased when the films were stratified. These results demonstrate that the PSA structure can be controlled through the processing conditions to achieve enhanced properties. This research will aid the future development of layered or graded single-deposition PSAs with designed adhesive properties.
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Affiliation(s)
- Toby R. Palmer
- Department
of Physics, University of Surrey, Guildford, SurreyGU2 7XH, U.K.
| | - Hanne M. van der Kooij
- Physical
Chemistry and Soft Matter, Wageningen University
and Research, 6708 WEWageningen, The Netherlands
| | - Rohani Abu Bakar
- Department
of Physics, University of Surrey, Guildford, SurreyGU2 7XH, U.K.
| | - Callum D. McAleese
- Surrey
Ion Beam Centre, University of Surrey, Guildford, SurreyGU2 7XH, U.K.
| | - Mathis Duewel
- Synthomer
Germany GmbH, Werrastraße 10, 45768Marl, Germany
| | - Katja Greiner
- Synthomer
Germany GmbH, Werrastraße 10, 45768Marl, Germany
| | - Pierre Couture
- Surrey
Ion Beam Centre, University of Surrey, Guildford, SurreyGU2 7XH, U.K.
| | - Matthew K. Sharpe
- Surrey
Ion Beam Centre, University of Surrey, Guildford, SurreyGU2 7XH, U.K.
| | - Joseph L. Keddie
- Department
of Physics, University of Surrey, Guildford, SurreyGU2 7XH, U.K.
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5
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In-situ and quantitative imaging of evaporation-induced stratification in binary suspensions. J Colloid Interface Sci 2023; 630:666-675. [DOI: 10.1016/j.jcis.2022.10.103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Revised: 10/05/2022] [Accepted: 10/20/2022] [Indexed: 11/06/2022]
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6
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Stratified and gradient films by evaporation-induced stratification of bimodal latexes. Potential of confocal and scanning electron microscopy for compositional depth profiling. POLYMER 2023. [DOI: 10.1016/j.polymer.2023.125752] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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7
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Kundu M, Howard MP. Dynamic density functional theory for drying colloidal suspensions: Comparison of hard-sphere free-energy functionals. J Chem Phys 2022; 157:184904. [DOI: 10.1063/5.0118695] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Dynamic density functional theory (DDFT) is a promising approach for predicting the structural evolution of a drying suspension containing one or more types of colloidal particles. The assumed free-energy functional is a key component of DDFT that dictates the thermodynamics of the model and, in turn, the density flux due to a concentration gradient. In this work, we compare several commonly used free-energy functionals for drying hard-sphere suspensions, including local-density approximations based on the ideal-gas, virial, and Boublík–Mansoori–Carnahan–Starling–Leland (BMCSL) equations of state as well as a weighted-density approximation based on fundamental measure theory (FMT). To determine the accuracy of each functional, we model one- and two-component hard-sphere suspensions in a drying film with varied initial heights and compositions, and we compare the DDFT-predicted volume fraction profiles to particle-based Brownian dynamics (BD) simulations. FMT accurately predicts the structure of the one-component suspensions even at high concentrations and when significant density gradients develop, but the virial and BMCSL equations of state provide reasonable approximations for smaller concentrations at a reduced computational cost. In the two-component suspensions, FMT and BMCSL are similar to each other but modestly overpredict the extent of stratification by size compared to BD simulations. This work provides helpful guidance for selecting thermodynamic models for soft materials in nonequilibrium processes, such as solvent drying, solvent freezing, and sedimentation.
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Affiliation(s)
- Mayukh Kundu
- Department of Chemical Engineering, Auburn University, Auburn, Alabama 36849, USA
| | - Michael P. Howard
- Department of Chemical Engineering, Auburn University, Auburn, Alabama 36849, USA
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8
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Park JS, Yun J, Chun B, Jung HW. Mild stratification in drying films of colloidal mixtures. SOFT MATTER 2022; 18:3487-3497. [PMID: 35438125 DOI: 10.1039/d2sm00205a] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Size stratification of bidisperse colloidal mixtures during vertical drying was investigated using the implicit solvent Langevin dynamics (LD) simulation and the explicit solvent lattice Boltzmann (LB) method. Simulations were performed for the Péclet number (Pe) over a wide range of 1-1000. In the case of a low size ratio of 2, mild stratification was observed in both simulation methods, in contrast to distinct stratification with thick "small-on-top" or "large-on-top" layers. The LD simulations exhibited a "small-on-top" stratification or mixed state. In contrast, the LB simulations exhibited a "large-on-top" or mixed state, according to the variation in Pe. The results demonstrated that the explicit solvent reduced the collective diffusion under moderate Pe conditions. This suppressed the steep concentration gradient of small particles in the packed region of particles near the air-solvent interface. Thus, distinguishable stratification patterns were obtained for the implicit and explicit solvent models.
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Affiliation(s)
- Jin Seok Park
- Department of Chemical and Biological Engineering, Korea University, Seoul 02841, Republic of Korea.
| | - Jinseong Yun
- Department of Chemical and Biological Engineering, Korea University, Seoul 02841, Republic of Korea.
| | - Byoungjin Chun
- Department of Chemical and Biological Engineering, Korea University, Seoul 02841, Republic of Korea.
| | - Hyun Wook Jung
- Department of Chemical and Biological Engineering, Korea University, Seoul 02841, Republic of Korea.
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9
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Hairy nanoparticles by atom transfer radical polymerization in miniemulsion. REACT FUNCT POLYM 2022. [DOI: 10.1016/j.reactfunctpolym.2021.105104] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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10
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Ge L, Luo C, You D, Yang N, Zhang Q, Yuan R, Wang J, Lu Z. Adhesion-enhanced coral cells with self-healing coating. Colloids Surf A Physicochem Eng Asp 2021. [DOI: 10.1016/j.colsurfa.2021.127337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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11
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Chiappara C, Arrabito G, Ferrara V, Scopelliti M, Sancataldo G, Vetri V, Chillura Martino DF, Pignataro B. Improved Photocatalytic Activity of Polysiloxane TiO 2 Composites by Thermally Induced Nanoparticle Bulk Clustering and Dye Adsorption. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:10354-10365. [PMID: 34461725 PMCID: PMC8413002 DOI: 10.1021/acs.langmuir.1c01475] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Revised: 07/27/2021] [Indexed: 05/24/2023]
Abstract
Fine control of nanoparticle clustering within polymeric matrices can be tuned to enhance the physicochemical properties of the resulting composites, which are governed by the interplay of nanoparticle surface segregation and bulk clustering. To this aim, out-of-equilibrium strategies can be leveraged to program the multiscale organization of such systems. Here, we present experimental results indicating that bulk assembly of highly photoactive clusters of titanium dioxide nanoparticles within an in situ synthesized polysiloxane matrix can be thermally tuned. Remarkably, the controlled nanoparticle clustering results in improved degradation photocatalytic performances of the material under 1 sun toward methylene blue. The resulting coatings, in particular the 35 wt % TiO2-loaded composites, show a photocatalytic degradation of about 80%, which was comparable to the equivalent amount of bare TiO2 and two-fold higher with respect to the corresponding composites not subjected to thermal treatment. These findings highlight the role of thermally induced bulk clustering in enhancing photoactive nanoparticle/polymer composite properties.
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Affiliation(s)
- Clara Chiappara
- Department
of Physics and Chemistry (DiFC) Emilio Segrè, University of Palermo, Building 17, V.le delle Scienze, Palermo 90128, Italy
- National
Interuniversity Consortium of Materials Science and Technology (INSTM),
UdR of Palermo, Florence 50121, Italy
| | - Giuseppe Arrabito
- Department
of Physics and Chemistry (DiFC) Emilio Segrè, University of Palermo, Building 17, V.le delle Scienze, Palermo 90128, Italy
| | - Vittorio Ferrara
- National
Interuniversity Consortium of Materials Science and Technology (INSTM),
UdR of Palermo, Florence 50121, Italy
- Department
of Biological, Chemical and Pharmaceutical Sciences and Technologies
(STEBICEF), University of Palermo, Building 16, V.le delle Scienze, Palermo 90128, Italy
| | - Michelangelo Scopelliti
- Department
of Physics and Chemistry (DiFC) Emilio Segrè, University of Palermo, Building 17, V.le delle Scienze, Palermo 90128, Italy
| | - Giuseppe Sancataldo
- Department
of Physics and Chemistry (DiFC) Emilio Segrè, University of Palermo, Building 17, V.le delle Scienze, Palermo 90128, Italy
| | - Valeria Vetri
- Department
of Physics and Chemistry (DiFC) Emilio Segrè, University of Palermo, Building 17, V.le delle Scienze, Palermo 90128, Italy
| | - Delia Francesca Chillura Martino
- National
Interuniversity Consortium of Materials Science and Technology (INSTM),
UdR of Palermo, Florence 50121, Italy
- Department
of Biological, Chemical and Pharmaceutical Sciences and Technologies
(STEBICEF), University of Palermo, Building 16, V.le delle Scienze, Palermo 90128, Italy
| | - Bruno Pignataro
- Department
of Physics and Chemistry (DiFC) Emilio Segrè, University of Palermo, Building 17, V.le delle Scienze, Palermo 90128, Italy
- National
Interuniversity Consortium of Materials Science and Technology (INSTM),
UdR of Palermo, Florence 50121, Italy
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12
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Neal T, Parnell AJ, King SM, Beattie DL, Murray MW, Williams NSJ, Emmett SN, Armes SP, Spain SG, Mykhaylyk OO. Control of Particle Size in the Self-Assembly of Amphiphilic Statistical Copolymers. Macromolecules 2021; 54:1425-1440. [PMID: 33583958 PMCID: PMC7879426 DOI: 10.1021/acs.macromol.0c02341] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Revised: 01/05/2021] [Indexed: 11/29/2022]
Abstract
A range of amphiphilic statistical copolymers is synthesized where the hydrophilic component is either methacrylic acid (MAA) or 2-(dimethylamino)ethyl methacrylate (DMAEMA) and the hydrophobic component comprises methyl, ethyl, butyl, hexyl, or 2-ethylhexyl methacrylate, which provide a broad range of partition coefficients (log P). Small-angle X-ray scattering studies confirm that these amphiphilic copolymers self-assemble to form well-defined spherical nanoparticles in an aqueous solution, with more hydrophobic copolymers forming larger nanoparticles. Varying the nature of the alkyl substituent also influenced self-assembly with more hydrophobic comonomers producing larger nanoparticles at a given copolymer composition. A model based on particle surface charge density (PSC model) is used to describe the relationship between copolymer composition and nanoparticle size. This model assumes that the hydrophilic monomer is preferentially located at the particle surface and provides a good fit to all of the experimental data. More specifically, a linear relationship is observed between the surface area fraction covered by the hydrophilic comonomer required to achieve stabilization and the log P value for the hydrophobic comonomer. Contrast variation small-angle neutron scattering is used to study the internal structure of these nanoparticles. This technique indicates partial phase separation within the nanoparticles, with about half of the available hydrophilic comonomer repeat units being located at the surface and hydrophobic comonomer-rich cores. This information enables a refined PSC model to be developed, which indicates the same relationship between the surface area fraction of the hydrophilic comonomer and the log P of the hydrophobic comonomer repeat units for the anionic (MAA) and cationic (DMAEMA) comonomer systems. This study demonstrates how nanoparticle size can be readily controlled and predicted using relatively ill-defined statistical copolymers, making such systems a viable attractive alternative to diblock copolymer nanoparticles for a range of industrial applications.
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Affiliation(s)
- Thomas
J. Neal
- Department
of Chemistry, The University of Sheffield, Dainton Building, Sheffield S3 7HF, U.K.
| | - Andrew J. Parnell
- Department
of Physics and Astronomy, The University
of Sheffield, Hicks Building, Sheffield S3 7RH, U.K.
| | - Stephen M. King
- ISIS
Pulsed Neutron and Muon Source, STFC Rutherford Appleton Laboratory, Harwell Campus, Didcot, Oxon OX11 0QX, U.K.
| | - Deborah L. Beattie
- Department
of Chemistry, The University of Sheffield, Dainton Building, Sheffield S3 7HF, U.K.
| | - Martin W. Murray
- AkzoNobel
Decorative Paints, Wexham
Road, Slough, Berkshire SL2 5DS, U.K.
| | | | - Simon N. Emmett
- AkzoNobel
Decorative Paints, Wexham
Road, Slough, Berkshire SL2 5DS, U.K.
| | - Steven P. Armes
- Department
of Chemistry, The University of Sheffield, Dainton Building, Sheffield S3 7HF, U.K.
| | - Sebastian G. Spain
- Department
of Chemistry, The University of Sheffield, Dainton Building, Sheffield S3 7HF, U.K.
| | - Oleksandr O. Mykhaylyk
- Department
of Chemistry, The University of Sheffield, Dainton Building, Sheffield S3 7HF, U.K.
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13
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Dong Y, Busatto N, Roth PJ, Martin-Fabiani I. Colloidal assembly of polydisperse particle blends during drying. SOFT MATTER 2020; 16:8453-8461. [PMID: 32812973 DOI: 10.1039/d0sm00785d] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
In this work, we synthesize a polydisperse aqueous colloidal system composed of small and large zwitterionic particles, as well as medium sized standard acrylic particles. By assembling these dispersions into films by drying, we show using atomic force microscopy (AFM) how their top surfaces can be mostly covered by zwitterionic groups for a wide range of evaporation rates. We probe underneath the top film surface using Fourier-transform infrared (FTIR) spectroscopy - attenuated total reflection (ATR), observing that the content in zwitterionic particles of the film upper layer increases for faster evaporation rates. We show how polydisperse systems hold great potential to overcome the evaporation rate dependence of size segregation processes in drying colloidal blends, and we provide further insights into the assembly mechanisms involved. Polydisperse blends enhance the robustness of such processes for application in coatings and other soft products where evaporation rate can not be tuned.
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Affiliation(s)
- Yichen Dong
- Department of Materials, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK.
| | - Nicolas Busatto
- Department of Chemistry, University of Surrey, Guildford, Surrey, GU2 7XH, UK
| | - Peter J Roth
- Department of Chemistry, University of Surrey, Guildford, Surrey, GU2 7XH, UK
| | - Ignacio Martin-Fabiani
- Department of Materials, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK.
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14
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Schulz M, Smith RW, Sear RP, Brinkhuis R, Keddie JL. Diffusiophoresis-Driven Stratification of Polymers in Colloidal Films. ACS Macro Lett 2020; 9:1286-1291. [PMID: 35638630 DOI: 10.1021/acsmacrolett.0c00363] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The molecular composition of polymer blend surfaces defines properties such as adhesion, wetting, gloss, and biocompatibility. The surface composition often differs from the bulk because of thermodynamic effects or modification. Mixtures of colloids and linear polymers in a common solvent are often used to deposit films for use in encapsulants, inks, coatings, and adhesives. However, means to control the nonequilibrium surface composition are lacking for these systems. Here we show how the surface composition and hydrophilicity of a film deposited from a bimodal mixture of linear polymers and colloids in water can be adjusted simply by varying the evaporation rate. Ion beam analysis was used to quantify the extent of stratification of the linear polymers near the surface, and the results are in agreement with a recent diffusiophoretic model. Because our approach to stratification relies solely on diffusiophoresis, it is widely applicable to any system deposited from colloids and nonadsorbing polymers in solution as a means to tailor surface properties.
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Affiliation(s)
- Malin Schulz
- Department of Physics, University of Surrey, Guildford, Surrey GU2 7XH, United Kingdom
| | - Richard W Smith
- Surrey Ion Beam Centre, University of Surrey, Guildford, Surrey GU2 7XH, United Kingdom
| | - Richard P Sear
- Department of Physics, University of Surrey, Guildford, Surrey GU2 7XH, United Kingdom
| | | | - Joseph L Keddie
- Department of Physics, University of Surrey, Guildford, Surrey GU2 7XH, United Kingdom
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15
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Howard MP, Nikoubashman A. Stratification of polymer mixtures in drying droplets: Hydrodynamics and diffusion. J Chem Phys 2020; 153:054901. [PMID: 32770900 DOI: 10.1063/5.0014429] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
We study the evaporation-induced stratification of a mixture of short and long polymer chains in a drying droplet using molecular simulations. We systematically investigate the effects of hydrodynamic interactions (HI) on this process by comparing hybrid simulations accounting for HI between polymers through the multiparticle collision dynamics technique with free-draining Langevin dynamics simulations neglecting the same. We find that the dried supraparticle morphologies are homogeneous when HI are included but are stratified in core-shell structures (with the short polymers forming the shell) when HI are neglected. The simulation methodology unambiguously attributes this difference to the treatment of the solvent in the two models. We rationalize the presence (or absence) of stratification by measuring phenomenological multicomponent diffusion coefficients for the polymer mixtures. The diffusion coefficients show the importance of not only solvent backflow but also HI between polymers in controlling the dried supraparticle morphology.
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Affiliation(s)
- Michael P Howard
- McKetta Department of Chemical Engineering, University of Texas at Austin, Austin, Texas 78712, USA
| | - Arash Nikoubashman
- Institute of Physics, Johannes Gutenberg University Mainz, Staudingerweg 7, 55128 Mainz, Germany
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16
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Zika A, Bernhardt S, Gröhn F. Photoresponsive Photoacid-Macroion Nano-Assemblies. Polymers (Basel) 2020; 12:E1746. [PMID: 32764323 PMCID: PMC7464814 DOI: 10.3390/polym12081746] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2020] [Revised: 07/27/2020] [Accepted: 07/31/2020] [Indexed: 01/01/2023] Open
Abstract
In this study, light-responsive nano-assemblies with light-switchable size based on photoacids are presented. Anionic disulfonated napthol derivates and cationic dendrimer macroions are used as building blocks for electrostatic self-assembly. Nanoparticles are already formed under the exclusion of light as a result of electrostatic interactions. Upon photoexcitation, an excited-state dissociation of the photoacidic hydroxyl group takes place, which leads to a more highly charged linker molecule and, subsequently, to a change in size and structure of the nano-assemblies. The effects of the charge ratio and the concentration on the stability have been examined with absorption spectroscopy and ζ-potential measurements. The influence of the chemical structure of three isomeric photoacids on the size and shape of the nanoscale aggregates has been studied by dynamic light scattering and atomic force microscopy, revealing a direct correlation of the strength of the photoacid with the changes of the assemblies upon irradiation.
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Affiliation(s)
| | | | - Franziska Gröhn
- Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular Materials, Friedrich-Alexander Universität Erlangen-Nürnberg, Egerlandstr. 3, D-91058 Erlangen, Germany; (A.Z.); (S.B.)
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17
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Grest GS. Stratification of drying particle suspensions: Comparison of implicit and explicit solvent simulations. J Chem Phys 2019; 150:224901. [DOI: 10.1063/1.5066035] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Affiliation(s)
- Gary S. Grest
- Sandia National Laboratories, Albuquerque, New Mexico 87185, USA
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18
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Tang Y, Grest GS, Cheng S. Control of Stratification in Drying Particle Suspensions via Temperature Gradients. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:4296-4304. [PMID: 30807180 DOI: 10.1021/acs.langmuir.8b03659] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
A potential strategy for controlling stratification in a drying suspension of bidisperse particles is studied using molecular dynamics simulations. When the suspension is maintained at a constant temperature during fast drying, it can exhibit "small-on-top" stratification with an accumulation (depletion) of smaller (larger) particles in the top region of the drying film, consistent with the prediction of current theories based on diffusiophoresis. However, when only the region near the substrate is thermalized at a constant temperature, a negative temperature gradient develops in the suspension because of evaporative cooling at the liquid-vapor interface. Since the associated thermophoresis is stronger for larger nanoparticles, a higher fraction of larger nanoparticles migrate to the top of the drying film at fast evaporation rates. As a result, stratification is converted to "large-on-top". Very strong small-on-top stratification can be produced with a positive thermal gradient in the drying suspension. Here, we explore a way to produce a positive thermal gradient by thermalizing the vapor at a temperature higher than that of the solvent. Possible experimental approaches to realize various thermal gradients in a suspension undergoing solvent evaporation and thus to produce different stratification states in the drying film are suggested.
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Affiliation(s)
- Yanfei Tang
- Department of Physics, Center for Soft Matter and Biological Physics, and Macromolecules Innovation Institute , Virginia Polytechnic Institute and State University , Blacksburg , Virginia 24061 , United States
| | - Gary S Grest
- Sandia National Laboratories , Albuquerque , New Mexico 87185 , United States
| | - Shengfeng Cheng
- Department of Physics, Center for Soft Matter and Biological Physics, and Macromolecules Innovation Institute , Virginia Polytechnic Institute and State University , Blacksburg , Virginia 24061 , United States
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19
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Schulz M, Keddie JL. A critical and quantitative review of the stratification of particles during the drying of colloidal films. SOFT MATTER 2018; 14:6181-6197. [PMID: 30024010 DOI: 10.1039/c8sm01025k] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
For a wide range of applications, films are deposited from colloidal particles suspended in a volatile liquid. There is burgeoning interest in stratifying colloidal particles into separate layers within the final dry film to impart properties at the surface different to the interior. Here, we outline the mechanisms by which colloidal mixtures can stratify during the drying process. The problem is considered here as a three-way competition between evaporation of the continuous liquid, sedimentation of particles, and their Brownian diffusion. In particle mixtures, the sedimentation of larger or denser particles offers one means of stratification. When the rate of evaporation is fast relative to diffusion, binary mixtures of large and small particles can stratify with small particles on the top, according to physical models and computer simulations. We compare experimental results found in the scientific literature to the predictions of several recent models in a quantitative way. Although there is not perfect agreement between them, some general trends emerge in the experiments, simulations and models. The stratification of small particles on the top of a film is favoured when the colloidal suspension is dilute but when both the concentration of the small particles and the solvent evaporation rate are sufficiently high. A higher particle size ratio also favours stratification by size. This review points to ways that microstructures can be designed and controlled in colloidal materials to achieve desired properties.
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Affiliation(s)
- M Schulz
- Department of Physics, University of Surrey, Guildford, Surrey GU2 7XH, England, UK.
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20
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Statt A, Howard MP, Panagiotopoulos AZ. Influence of hydrodynamic interactions on stratification in drying mixtures. J Chem Phys 2018; 149:024902. [DOI: 10.1063/1.5031789] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Affiliation(s)
- Antonia Statt
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, USA
| | - Michael P. Howard
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, USA
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21
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Tang Y, Grest GS, Cheng S. Stratification in Drying Films Containing Bidisperse Mixtures of Nanoparticles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:7161-7170. [PMID: 29792029 DOI: 10.1021/acs.langmuir.8b01334] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Large scale molecular dynamics simulations for bidisperse nanoparticle suspensions with an explicit solvent are used to investigate the effects of evaporation rates and volume fractions on the nanoparticle distribution during drying. Our results show that "small-on-top" stratification can occur when Pe sϕ s ≳ c with c ∼ 1, where Pe s is the Péclet number and ϕ s is the volume fraction of the smaller particles. This threshold of Pe sϕ s for "small-on-top" is larger by a factor of ∼α2 than the prediction of the model treating solvent as an implicit viscous background, where α is the size ratio between the large and small particles. Our simulations further show that when the evaporation rate of the solvent is reduced, the "small-on-top" stratification can be enhanced, which is not predicted by existing theories. This unexpected behavior is explained with thermophoresis associated with a positive gradient of solvent density caused by evaporative cooling at the liquid/vapor interface. For ultrafast evaporation the gradient is large and drives the nanoparticles toward the liquid/vapor interface. This phoretic effect is stronger for larger nanoparticles, and consequently the "small-on-top" stratification becomes more distinct when the evaporation rate is slower (but not too slow such that a uniform distribution of nanoparticles in the drying film is produced), as thermophoresis that favors larger particles on the top is mitigated. A similar effect can lead to "large-on-top" stratification for Pe sϕ s above the threshold when Pe s is large but ϕ s is small. Our results reveal the importance of including the solvent explicitly when modeling evaporation-induced particle separation and organization and point to the important role of density gradients brought about by ultrafast evaporation.
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Affiliation(s)
- Yanfei Tang
- Department of Physics, Center for Soft Matter and Biological Physics, and Macromolecules Innovation Institute , Virginia Polytechnic Institute and State University , Blacksburg , Virginia 24061 , United States
| | - Gary S Grest
- Sandia National Laboratories, Albuquerque , New Mexico 87185 , United States
| | - Shengfeng Cheng
- Department of Physics, Center for Soft Matter and Biological Physics, and Macromolecules Innovation Institute , Virginia Polytechnic Institute and State University , Blacksburg , Virginia 24061 , United States
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22
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Cusola O, Kivistö S, Vierros S, Batys P, Ago M, Tardy BL, Greca LG, Roncero MB, Sammalkorpi M, Rojas OJ. Particulate Coatings via Evaporation-Induced Self-Assembly of Polydisperse Colloidal Lignin on Solid Interfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:5759-5771. [PMID: 29718673 PMCID: PMC6150720 DOI: 10.1021/acs.langmuir.8b00650] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Revised: 04/04/2018] [Indexed: 05/19/2023]
Abstract
Polydisperse smooth and spherical biocolloidal particles were suspended in aqueous media and allowed to consolidate via evaporation-induced self-assembly. The stratification of the particles at the solid-air interface was markedly influenced, but not monotonically, by the drying rate. Cross-sectional imaging via electron microscopy indicated a structured coating morphology that was distinctive from that obtained by using particles with a mono- or bimodal distribution. Segregation patterns were found to derive from the interplay of particle diffusion, interparticle forces, and settling dynamics. Supporting our experimental findings, computer simulations showed an optimal drying rate for achieving maximum segregation. Overall, stratified coatings comprising nano- and microparticles derived from lignin are expected to open opportunities for multifunctional structures that can be designed and predicted on the basis of experimental Péclet numbers and computational order.
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Affiliation(s)
- Oriol Cusola
- Department
of Bioproducts and Biosystems, School of Chemical Engineering, Department of Chemistry
and Materials Science, School of Chemical Engineering, and Department of
Applied Physics, School of Science, Aalto
University, FI-00076 Aalto, Finland
- CELBIOTECH
Research Group, Escola Superior d’Enginyeries
Industrial, Aeroespacial i Audiovisual de Terrassa, 08222 Terrassa, Spain
- E-mail: (O.C.)
| | - Samu Kivistö
- Department
of Bioproducts and Biosystems, School of Chemical Engineering, Department of Chemistry
and Materials Science, School of Chemical Engineering, and Department of
Applied Physics, School of Science, Aalto
University, FI-00076 Aalto, Finland
| | - Sampsa Vierros
- Department
of Bioproducts and Biosystems, School of Chemical Engineering, Department of Chemistry
and Materials Science, School of Chemical Engineering, and Department of
Applied Physics, School of Science, Aalto
University, FI-00076 Aalto, Finland
| | - Piotr Batys
- Department
of Bioproducts and Biosystems, School of Chemical Engineering, Department of Chemistry
and Materials Science, School of Chemical Engineering, and Department of
Applied Physics, School of Science, Aalto
University, FI-00076 Aalto, Finland
- Jerzy
Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Niezapominajek 8, PL-30239 Krakow, Poland
| | - Mariko Ago
- Department
of Bioproducts and Biosystems, School of Chemical Engineering, Department of Chemistry
and Materials Science, School of Chemical Engineering, and Department of
Applied Physics, School of Science, Aalto
University, FI-00076 Aalto, Finland
| | - Blaise L. Tardy
- Department
of Bioproducts and Biosystems, School of Chemical Engineering, Department of Chemistry
and Materials Science, School of Chemical Engineering, and Department of
Applied Physics, School of Science, Aalto
University, FI-00076 Aalto, Finland
| | - Luiz G. Greca
- Department
of Bioproducts and Biosystems, School of Chemical Engineering, Department of Chemistry
and Materials Science, School of Chemical Engineering, and Department of
Applied Physics, School of Science, Aalto
University, FI-00076 Aalto, Finland
| | - M. Blanca Roncero
- CELBIOTECH
Research Group, Escola Superior d’Enginyeries
Industrial, Aeroespacial i Audiovisual de Terrassa, 08222 Terrassa, Spain
| | - Maria Sammalkorpi
- Department
of Bioproducts and Biosystems, School of Chemical Engineering, Department of Chemistry
and Materials Science, School of Chemical Engineering, and Department of
Applied Physics, School of Science, Aalto
University, FI-00076 Aalto, Finland
| | - Orlando J. Rojas
- Department
of Bioproducts and Biosystems, School of Chemical Engineering, Department of Chemistry
and Materials Science, School of Chemical Engineering, and Department of
Applied Physics, School of Science, Aalto
University, FI-00076 Aalto, Finland
- E-mail: (O.J.R.)
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23
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Sear RP. Stratification of mixtures in evaporating liquid films occurs only for a range of volume fractions of the smaller component. J Chem Phys 2018; 148:134909. [DOI: 10.1063/1.5022243] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Affiliation(s)
- Richard P. Sear
- Department of Physics, University of Surrey, Guildford GU2 7XH, United Kingdom
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24
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Zhou J, Man X, Jiang Y, Doi M. Structure Formation in Soft-Matter Solutions Induced by Solvent Evaporation. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2017; 29:1703769. [PMID: 29058825 DOI: 10.1002/adma.201703769] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Revised: 08/10/2017] [Indexed: 06/07/2023]
Abstract
Solvent evaporation in soft-matter solutions (solutions of colloidal particles, polymers, and their mixtures) is an important process in material making and in the printing and coating industries. The solvent-evaporation process determines the structure of materials and strongly affects their performance. Solvent evaporation involves many physicochemical processes: flow, diffusion, crystallization, gelation, glass transition, etc. and is quite complex. Here, recent progress in this important process is reported, with a special focus on theoretical and simulation studies.
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Affiliation(s)
- Jiajia Zhou
- Key Laboratory of Bio-inspired Smart Interfacial Science and Technology of Ministry of Education, School of Chemistry, Beihang University, Beijing, 100191, P. R. China
- Center of Soft Matter Physics and Its Applications, Beihang University, Beijing, 100191, P. R. China
| | - Xingkun Man
- Center of Soft Matter Physics and Its Applications, Beihang University, Beijing, 100191, P. R. China
- School of Physics and Nuclear Energy Engineering, Beihang University, Beijing, 100191, P. R. China
| | - Ying Jiang
- Key Laboratory of Bio-inspired Smart Interfacial Science and Technology of Ministry of Education, School of Chemistry, Beihang University, Beijing, 100191, P. R. China
- Center of Soft Matter Physics and Its Applications, Beihang University, Beijing, 100191, P. R. China
| | - Masao Doi
- Center of Soft Matter Physics and Its Applications, Beihang University, Beijing, 100191, P. R. China
- Beijing Advanced Innovation Center for Biomedical Engineering, Beihang University, Beijing, 100191, P. R. China
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25
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Sear RP, Warren PB. Diffusiophoresis in nonadsorbing polymer solutions: The Asakura-Oosawa model and stratification in drying films. Phys Rev E 2017; 96:062602. [PMID: 29347396 DOI: 10.1103/physreve.96.062602] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Indexed: 05/01/2023]
Abstract
A colloidal particle placed in an inhomogeneous solution of smaller nonadsorbing polymers will move towards regions of lower polymer concentration in order to reduce the free energy of the interface between the surface of the particle and the solution. This phenomenon is known as diffusiophoresis. Treating the polymer as penetrable hard spheres, as in the Asakura-Oosawa model, a simple analytic expression for the diffusiophoretic drift velocity can be obtained. In the context of drying films we show that diffusiophoresis by this mechanism can lead to stratification under easily accessible experimental conditions. By stratification we mean spontaneous formation of a layer of polymer on top of a layer of the colloid. Transposed to the case of binary colloidal mixtures, this offers an explanation for the stratification observed recently in these systems [A. Fortini et al., Phys. Rev. Lett. 116, 118301 (2016)PRLTAO0031-900710.1103/PhysRevLett.116.118301]. Our results emphasize the importance of treating solvent dynamics explicitly in these problems and caution against the neglect of hydrodynamic interactions or the use of implicit solvent models in which the absence of solvent backflow results in an unbalanced osmotic force that gives rise to large but unphysical effects.
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Affiliation(s)
- Richard P Sear
- Department of Physics, University of Surrey, Guildford GU2 7XH, United Kingdom
| | - Patrick B Warren
- Unilever R&D Port Sunlight, Quarry Road East, Bebington, Wirral CH63 3JW, United Kingdom
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26
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Howard MP, Nikoubashman A, Panagiotopoulos AZ. Stratification in Drying Polymer-Polymer and Colloid-Polymer Mixtures. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:11390-11398. [PMID: 28793766 DOI: 10.1021/acs.langmuir.7b02074] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Drying polymer-polymer and colloid-polymer mixtures were studied using Langevin dynamics computer simulations. Polymer-polymer mixtures vertically stratified into layers, with the shorter polymers enriched near the drying interface and the longer polymers pushed down toward the substrate. Colloid-polymer mixtures stratified into a polymer-on-top structure when the polymer radius of gyration was comparable to or smaller than the colloid diameter, and a colloid-on-top structure otherwise. We also developed a theoretical model for the drying mixtures based on dynamical density functional theory, which gave excellent quantitative agreement with the simulations for the polymer-polymer mixtures and qualitatively predicted the observed polymer-on-top or colloid-on-top structures for the colloid-polymer mixtures.
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Affiliation(s)
- Michael P Howard
- Department of Chemical and Biological Engineering, Princeton University , Princeton, New Jersey 08544, United States of America
| | - Arash Nikoubashman
- Institute of Physics, Johannes Gutenberg University Mainz , Staudingerweg 7, 55128 Mainz, Germany
| | - Athanassios Z Panagiotopoulos
- Department of Chemical and Biological Engineering, Princeton University , Princeton, New Jersey 08544, United States of America
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27
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Makepeace DK, Fortini A, Markov A, Locatelli P, Lindsay C, Moorhouse S, Lind R, Sear RP, Keddie JL. Stratification in binary colloidal polymer films: experiment and simulations. SOFT MATTER 2017; 13:6969-6980. [PMID: 28920986 DOI: 10.1039/c7sm01267e] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
UNLABELLED When films are deposited from mixtures of colloidal particles of two different sizes, a diverse range of functional structures can result. One structure of particular interest is a stratified film in which the top surface layer has a composition different than in the interior. Here, we explore the conditions under which a stratified layer of small particles develops spontaneously in a colloidal film that is cast from a binary mixture of small and large polymer particles that are suspended in water. A recent model, which considers the cross-interaction between the large and small particles (Zhou et al., Phys. Rev. Lett., 2017, 118, 108002), predicts that stratification will develop from dilute binary mixtures when the particle size ratio (α), initial volume fraction of small particles (ϕS), and Péclet number are high. In experiments and Langevin dynamics simulations, we systematically vary α and ϕS in both dilute and concentrated suspensions. We find that stratified films develop when ϕS is increased, which is in agreement with the model. In dilute suspensions, there is reasonable agreement between the experiments and the Zhou et al. MODEL In concentrated suspensions, stratification occurs in experiments only for the higher size ratio α = 7. Simulations using a high Péclet number, additionally find stratification with α = 2, when ϕS is high enough. Our results provide a quantitative understanding of the conditions under which stratified colloidal films assemble. Our research has relevance for the design of coatings with targeted optical and mechanical properties at their surface.
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Affiliation(s)
- D K Makepeace
- Department of Physics, University of Surrey, Guildford, Surrey GU2 7XH, UK.
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28
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Physicochemical properties and esterolytic reactivity of oxime functionalized surfactants in pH-responsive mixed micellar system. Colloids Surf A Physicochem Eng Asp 2017. [DOI: 10.1016/j.colsurfa.2017.04.039] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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29
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Howard MP, Nikoubashman A, Panagiotopoulos AZ. Stratification Dynamics in Drying Colloidal Mixtures. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:3685-3693. [PMID: 28349690 DOI: 10.1021/acs.langmuir.7b00543] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Stratification in binary colloidal mixtures was investigated using implicit-solvent molecular dynamics simulations. For large particle size ratios and film Péclet numbers greater than unity, smaller colloids migrated to the top of the film, while big colloids were pushed to the bottom, creating an "inverted" stratification. This peculiar behavior was observed in recent simulations and experiments conducted by Fortini et al. [ Phys. Rev. Lett. 2016 , 116 , 118301 ]. To rationalize this behavior, particle size ratios and drying rates spanning qualitatively different Péclet number regimes were systematically studied, and the dynamics of the inverted stratification were quantified in detail. The stratified layer of small colloids was found to grow faster and to larger thicknesses for larger size ratios. Interestingly, inverted stratification was observed even at moderate drying rates where the film Péclet numbers were comparable to unity, but the thickness of the stratified layer decreased. A model based on dynamical density functional theory is proposed to explain the observed phenomena.
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Affiliation(s)
- Michael P Howard
- Department of Chemical and Biological Engineering, Princeton University , Princeton, New Jersey 08544, United States
| | - Arash Nikoubashman
- Institute of Physics, Johannes Gutenberg University Mainz , Staudingerweg 7, 55128 Mainz, Germany
| | - Athanassios Z Panagiotopoulos
- Department of Chemical and Biological Engineering, Princeton University , Princeton, New Jersey 08544, United States
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