1
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Kim BQ, Kim JQ, Yoon H, Lee E, Choi SQ, Kim K. Active Stratification of Colloidal Mixtures for Asymmetric Multilayers. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024:e2404348. [PMID: 39150055 DOI: 10.1002/smll.202404348] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2024] [Revised: 08/05/2024] [Indexed: 08/17/2024]
Abstract
Stratified films offer high performance and multifunctionality, yet achieving fully stratified films remains a challenge. The layer-by-layer method, involving the sequential deposition of each layer, has been commonly utilized for stratified film fabrication. However, this approach is time-consuming, labor-intensive, and prone to leaving defects within the film. Alternatively, the self-stratification process exploiting a drying binary colloidal mixture is intensively developed recently, but it relies on strict operating conditions, typically yielding a heterogeneous interlayer. In this study, an active interfacial stratification process for creating completely stratified nanoparticle (NP) films is introduced. The technique leverages NPs with varying interfacial activity at the air-water interface. With the help of depletion pressure, the lateral compression of NP mixtures at the interface induces individual desorption of less interfacial active NPs into the subphase, while more interfacial active NPs remain at the interface. This simple compression leads to nearly perfect stratified NP films with controllability, universality, and scalability. Combined with a solvent annealing process, the active stratification process enables the fabrication of stratified films comprising a polymeric layer atop a NP layer. This work provides insightful implications for designing drug encapsulation and controlled release, as well as manufacturing transparent and flexible electrodes.
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Affiliation(s)
- Baekmin Q Kim
- Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea
| | - Jongmin Q Kim
- Interface Materials and Chemical Engineering Research Center, Korea Research Institute of Chemical Technology (KRICT), Daejeon, 34114, Republic of Korea
| | - Hojoon Yoon
- Department of Chemical and Biomolecular Engineering, Seoul National University of Science and Technology (SeoulTech), Seoul, 01811, Republic of Korea
| | - EunSuk Lee
- Department of Chemical and Biomolecular Engineering, Seoul National University of Science and Technology (SeoulTech), Seoul, 01811, Republic of Korea
| | - Siyoung Q Choi
- Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, 34141, Republic of Korea
- KAIST Institute for the Nanocentury, KAIST, Daejeon, 34141, Republic of Korea
| | - KyuHan Kim
- Department of Chemical and Biomolecular Engineering, Seoul National University of Science and Technology (SeoulTech), Seoul, 01811, Republic of Korea
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2
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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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3
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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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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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Singh PK, Pacholski ML, Gu J, Go YK, Singhal G, Leal C, Braun PV, Patankar KA, Drumright R, Rogers SA, Schroeder CM. Designing Multicomponent Polymer Colloids for Self-Stratifying Films. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:11160-11170. [PMID: 36053575 DOI: 10.1021/acs.langmuir.2c00855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Aqueous polymer colloids known as latexes are widely used in coating applications. Multicomponent latexes comprised of two incompatible polymeric species organized into a core-shell particle morphology are a promising system for self-stratifying coatings that spontaneously partition into multiple layers, thereby yielding complex structured coatings requiring only a single application step. Developing new materials for self-stratifying coatings requires a clear understanding of the thermodynamic and kinetic properties governing phase separation and polymeric species transport. In this work, we study phase separation and self-stratification in polymer films based on multicomponent acrylic (shell) and acrylic-silicone (core) latex particles. Our results show that the molecular weight of the shell polymer and heat aging conditions of the film critically determine the underlying transport phenomena, which ultimately controls phase separation in the film. Unentangled shell polymers result in efficient phase separation within hours with heat aging at reasonable temperatures, whereas entangled shell polymers effectively inhibit phase separation even under extensive heat aging conditions over a period of months due to kinetic limitations. Transmission electron microscopy is used to track morphological changes as a function of thermal aging. Interestingly, our results show that the rheological properties of the latex films are highly sensitive to morphology, and linear shear rheology is used to understand morphological changes. Overall, these results highlight the importance of bulk rheology as a simple and effective tool for understanding changes in morphology in multicomponent latex films.
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Affiliation(s)
| | | | - Junsi Gu
- The Dow Chemical Company, Collegeville, Pennsylvania 19426-2914, United States
| | | | | | | | | | | | - Ray Drumright
- The Dow Chemical Company, Midland, Michigan 48667, United States
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9
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Tinkler JD, Scacchi A, Argaiz M, Tomovska R, Archer AJ, Willcock H, Martín-Fabiani I. Effect of Particle Interactions on the Assembly of Drying Colloidal Mixtures. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:5361-5371. [PMID: 35439018 PMCID: PMC9097527 DOI: 10.1021/acs.langmuir.1c03144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Revised: 03/17/2022] [Indexed: 06/14/2023]
Abstract
The effects of particle interactions on the size segregation and assembly of colloidal mixtures during drying were investigated. A cationic surfactant was added to a binary latex/silica colloidal dispersion that has been shown to self-stratify upon drying at room temperature. Atomic force microscopy was used to show that the change in particle interactions due to the presence of surfactants reduced the degree of stratification and, in some cases, suppressed the effect altogether. Colloidal dispersions containing higher surfactant concentrations can undergo a complete morphology change, resulting instead in the formation of armored particles consisting of latex particles coated with smaller silica nanoparticles. To further prove that armored particles are produced and that stratification is suppressed, cross-sectional images were produced with energy-dispersive X-ray spectroscopy and confocal fluorescence microscopy. The growth of armored particles was also measured using dynamic light scattering. To complement this research, Brownian dynamics simulations were used to model the drying. By tuning the particle interactions to make them more attractive, the simulations showed the presence of armored particles, and the size segregation process was hindered. The prevention of segregation also results in enhanced transparency of the colloidal films. Overall, this research proves that there is a link between particle interactions and size segregation in drying colloidal blends and provides a valuable tool to control the assembly of different film architectures using an extremely simple method.
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Affiliation(s)
- James D. Tinkler
- Department
of Materials, Loughborough University, Loughborough LE11 3TU, U.K.
| | - Alberto Scacchi
- Department
of Chemistry and Materials Science, Aalto
University, P.O. Box 16100, FI-00076 Aalto, Finland
- Department
of Applied Physics, Aalto University, P.O. Box 11000, FI-00076 Aalto, Finland
| | - Maialen Argaiz
- POLYMAT
and Departmento de Química Aplicada, Facultad de Ciencias Químicas, University of the Basque Country, UPV/EHU, Joxe Mari
Korta Zentroa, Tolosa Hiribidea 72, Donostia-San Sebastian 20018, Spain
| | - Radmila Tomovska
- POLYMAT
and Departmento de Química Aplicada, Facultad de Ciencias Químicas, University of the Basque Country, UPV/EHU, Joxe Mari
Korta Zentroa, Tolosa Hiribidea 72, Donostia-San Sebastian 20018, Spain
- Ikerbasque,
Basque Foundation for Science, Maria Diaz de Haro 3, 48013 Bilbao, Spain
| | - Andrew J. Archer
- Department
of Mathematical Sciences and Interdisciplinary Centre for Mathematical
Modelling, Loughborough University, Loughborough LE11 3TU, U.K.
| | - Helen Willcock
- Department
of Materials, Loughborough University, Loughborough LE11 3TU, U.K.
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10
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Schulz M, Brinkhuis R, Crean C, Sear RP, Keddie JL. Suppression of self-stratification in colloidal mixtures with high Péclet numbers. SOFT MATTER 2022; 18:2512-2516. [PMID: 35297936 DOI: 10.1039/d2sm00194b] [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
The non-equilibrium assembly of bimodal colloids during evaporative processes is an attractive means to achieve gradient or stratified layers in thick films. Here, we show that the stratification of small colloids on top of large is prevented when the viscosity of the continuous aqueous phase is too high. We propose a model where a too narrow width of the gradient in concentration of small colloids suppresses the stratification.
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Affiliation(s)
- M Schulz
- Department of Physics, University of Surrey, Guildford, Surrey, GU2 7XH, UK.
| | - R Brinkhuis
- Allnex, Nieuwe Kanaal 7N, 6709 PA Wageningen, The Netherlands
| | - C Crean
- Department of Chemistry, University of Surrey, Guildford, Surrey, GU2 7XH, UK
| | - R P Sear
- Department of Physics, University of Surrey, Guildford, Surrey, GU2 7XH, UK.
| | - J L Keddie
- Department of Physics, University of Surrey, Guildford, Surrey, GU2 7XH, UK.
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11
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Liu W, Shen J, Bhatia SR. An in-situ SAXS approach to probe stratification during drying of inorganic nanoparticle films. Inorganica Chim Acta 2021. [DOI: 10.1016/j.ica.2020.120213] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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12
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Tinkler JD, Scacchi A, Kothari HR, Tulliver H, Argaiz M, Archer AJ, Martín-Fabiani I. Evaporation-driven self-assembly of binary and ternary colloidal polymer nanocomposites for abrasion resistant applications. J Colloid Interface Sci 2021; 581:729-740. [PMID: 32818678 DOI: 10.1016/j.jcis.2020.08.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Revised: 07/10/2020] [Accepted: 08/01/2020] [Indexed: 10/23/2022]
Abstract
We harness the self-assembly of aqueous binary latex/silica particle blends during drying to fabricate films segregated by size in the vertical direction. We report for the first time the experimental drying of ternary colloidal dispersions and demonstrate how a ternary film containing additional small latex particles results in improved surface stability and abrasion resistance compared with a binary film. Through atomic force microscopy (AFM) and energy-dispersive X-ray spectroscopy (EDX), we show that the vertical distribution of filler particles and the surface morphologies of the films can be controlled by altering the evaporation rate and silica volume fraction. We report the formation of various silica superstructures at the film surface, which we attribute to a combination of diffusiophoresis and electrostatic interactions between particles. Brownian dynamics simulations of the final stages of solvent evaporation provide further evidence for this formation mechanism. We show how an additional small latex particle population results in an increased abrasion resistance of the film without altering its morphology or hardness. Our work provides a method to produce water-based coatings with enhanced abrasion resistance as well as valuable insights into the mechanisms behind the formation of colloidal superstructures.
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Affiliation(s)
- James D Tinkler
- Department of Materials, Loughborough University, Loughborough, UK.
| | - Alberto Scacchi
- Department of Mathematical Sciences, Loughborough University, Loughborough, UK
| | - Harsh R Kothari
- Department of Materials, Loughborough University, Loughborough, UK
| | - Hanna Tulliver
- Department of Materials, Loughborough University, Loughborough, UK
| | - Maialen Argaiz
- POLYMAT and Departmento de Química Aplicada, Facultad de Ciencias Químicas, University of the Basque Country, UPV/EHU, Donostia-San Sebastian, Spain
| | - Andrew J Archer
- Department of Mathematical Sciences, Loughborough University, Loughborough, UK
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13
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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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14
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Inoue K, Inasawa S. Drying-induced back flow of colloidal suspensions confined in thin unidirectional drying cells. RSC Adv 2020; 10:15763-15768. [PMID: 35493636 PMCID: PMC9052441 DOI: 10.1039/d0ra02837a] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2020] [Accepted: 04/14/2020] [Indexed: 12/31/2022] Open
Abstract
A clear back flow was observed in the thin unidirectional drying cell of a colloidal suspension. Flow around the colloidal-particle packing front was more complex than expected, even though a colloidal suspension was confined in a narrow space with a submillimeter-scale or shorter gap height. We propose that an increase in particle concentration around the packing front induces downward flow, which is the origin for back flow inside the cell. A mathematical model, which considered both a drying induced horizontal flow and a circulation flow caused by a concentration gradient of particles, showed a reasonable agreement with experimental data for the width of the back-flow region. The concentration gradient of particles was not negligible and it generated a rather complicated flow even in a thin drying liquid film.
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Affiliation(s)
- Kai Inoue
- Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology 2-24-16 Nakacho, Koganei Tokyo 184-8588 Japan +81-42-388-7798 +81-42-388-7105
| | - Susumu Inasawa
- Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology 2-24-16 Nakacho, Koganei Tokyo 184-8588 Japan +81-42-388-7798 +81-42-388-7105
- Department of Chemical Engineering, Tokyo University of Agriculture and Technology 2-24-16 Nakacho, Koganei Tokyo 184-8588 Japan
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15
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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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16
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Liu W, Midya J, Kappl M, Butt HJ, Nikoubashman A. Segregation in Drying Binary Colloidal Droplets. ACS NANO 2019; 13:4972-4979. [PMID: 30897326 PMCID: PMC6727607 DOI: 10.1021/acsnano.9b00459] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Accepted: 03/21/2019] [Indexed: 05/14/2023]
Abstract
When a colloidal suspension droplet evaporates from a solid surface, it leaves a characteristic deposit in the contact region. These deposits are common and important for many applications in printing, coating, or washing. By the use of superamphiphobic surfaces as a substrate, the contact area can be reduced so that evaporation is almost radially symmetric. While drying, the droplets maintain a nearly perfect spherical shape. Here, we exploit this phenomenon to fabricate supraparticles from bidisperse colloidal aqueous suspensions. The supraparticles have a core-shell morphology. The outer region is predominantly occupied by small colloids, forming a close-packed crystalline structure. Toward the center, the number of large colloids increases and they are packed amorphously. The extent of this stratification decreases with decreasing the evaporation rate. Complementary simulations indicate that evaporation leads to a local increase in density, which, in turn, exerts stronger inward forces on the larger colloids. A comparison between experiments and simulations suggest that hydrodynamic interactions between the suspended colloids reduce the extent of stratification. Our findings are relevant for the fabrication of supraparticles for applications in the fields of chromatography, catalysis, drug delivery, photonics, and a better understanding of spray-drying.
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Affiliation(s)
- Wendong Liu
- Department
of Physics at Interfaces, Max Planck Institute
for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany
| | - Jiarul Midya
- Institute
of Physics, Johannes Gutenberg University
Mainz, Staudingerweg 7, D-55128 Mainz, Germany
| | - Michael Kappl
- Department
of Physics at Interfaces, Max Planck Institute
for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany
| | - Hans-Jürgen Butt
- Department
of Physics at Interfaces, Max Planck Institute
for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany
| | - Arash Nikoubashman
- Institute
of Physics, Johannes Gutenberg University
Mainz, Staudingerweg 7, D-55128 Mainz, Germany
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17
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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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18
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Liu W, Carr AJ, Yager KG, Routh AF, Bhatia SR. Sandwich layering in binary nanoparticle films and effect of size ratio on stratification behavior. J Colloid Interface Sci 2019; 538:209-217. [PMID: 30508741 DOI: 10.1016/j.jcis.2018.11.084] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Revised: 11/21/2018] [Accepted: 11/22/2018] [Indexed: 10/27/2022]
Abstract
HYPOTHESIS Stratification or self-segregation of multicomponent particle mixtures during drying is an important phenomenon to understand for the development of single-step deposition processes for complex coatings. We hypothesize that varying the ratio of particle Peclet numbers will lead to different types of stratification behavior. EXPERIMENTS Binary colloidal films of polystyrene and silica were prepared by evaporative film formation, and stratification of nanoparticles of different size ratio (7.7-1.2) was studied using microbeam small-angle X-ray scattering (SAXS). FINDINGS SAXS spectra showed noticeable variations at different film depths, consistent with stratification. These results are quantified to obtain vertical composition profiles. We observe "sandwich"-type layered structures at different nanoparticle size ratios, which to our knowledge have not been previously observed experimentally or predicted by theory. For example, for films of larger particle size ratios (7.7-4.8), large particles are enriched at the film top and bottom, leading to a large-small-large or "LSL" behavior; while within films of smaller particle size ratio (2.2-1.2), small particles are enriched at the top and bottom of the film (small-large-small or "SLS" structures). The enrichment of particles at the top persists over several hundred particle layers and is not just a single monolayer pinned to the upper surface.
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Affiliation(s)
- Weiping Liu
- Department of Chemistry, Stony Brook University, Stony Brook, NY, USA
| | - Amanda J Carr
- Department of Chemistry, Stony Brook University, Stony Brook, NY, USA
| | - Kevin G Yager
- Center for Functionalized Nanomaterials, Brookhaven National Laboratory, Upton, NY, USA
| | - Alexander F Routh
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Pembroke Street, Cambridge CB2 3RA, United Kingdom
| | - Surita R Bhatia
- Department of Chemistry, Stony Brook University, Stony Brook, NY, USA.
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19
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Gregson FKA, Robinson JF, Miles REH, Royall CP, Reid JP. Drying Kinetics of Salt Solution Droplets: Water Evaporation Rates and Crystallization. J Phys Chem B 2018; 123:266-276. [DOI: 10.1021/acs.jpcb.8b09584] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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20
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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: 51] [Impact Index Per Article: 8.5] [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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21
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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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22
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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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Sol-gel synthesis of Bi2WO6/graphene thin films with enhanced photocatalytic performance for nitric monoxide oxidation under visible light irradiation. Chem Phys Lett 2018. [DOI: 10.1016/j.cplett.2018.04.052] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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24
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Advanced Heterogeneous Fenton Treatment of Coalbed Methane-Produced Water Containing Fracturing Fluid. Processes (Basel) 2018. [DOI: 10.3390/pr6050040] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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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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