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Stetten AZ, Treece BW, Corcoran TE, Garoff S, Przybycien TM, Tilton RD. Evolution and Disappearance of Solvent Drops on Miscible Polymer Subphases. Colloids Surf A Physicochem Eng Asp 2018; 546:266-275. [PMID: 30416264 DOI: 10.1016/j.colsurfa.2018.03.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Traditionally, an interface is defined as a boundary between immiscible phases. However, previous work has shown that even when two fluids are completely miscible, they maintain a detectable "effective interface" for long times. Miscible interfaces have been studied in various systems of two fluids with a single boundary between them. However, this work has not extended to the three-phase system of a fluid droplet placed on top of a miscible pool. We show that these three-phase systems obey the same wetting conditions as immiscible systems, and that their drop shapes obey the Augmented Young-Laplace Equation. Over time, the miscible interface diffuses and the shape of the drop evolves. We place 2-microliter drops of water atop miscible poly(acrylamide) solutions. The drop is completely wetted by the subphase, and then remains detectable beneath the surface for many minutes. An initial effective interfacial tension can be approximated to be on the order of 0.5 mN/m using the capillary number. Water and poly(acrylamide) are completely miscible in all concentrations, and yet, when viewed from the side, the drop maintains a capillary shape. Study of this behavior is important to the understanding of effective interfaces between miscible polymer phases, which are pervasive in nature.
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Affiliation(s)
- Amy Z Stetten
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Bradley W Treece
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Timothy E Corcoran
- Department of Medicine, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Stephen Garoff
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Todd M Przybycien
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA.,Department of Medicine, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Robert D Tilton
- Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA.,Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA
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Perazzo CA, Mac Intyre JR, Gomba JM. Analytical solutions for the profile of two-dimensional droplets with finite-length precursor films. Phys Rev E 2017; 96:063109. [PMID: 29347321 DOI: 10.1103/physreve.96.063109] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Indexed: 06/07/2023]
Abstract
By means of the lubrication approximation we obtain the full family of static bidimensional profiles of a liquid resting on a substrate under partial-wetting conditions imposed by a disjoining-conjoining pressure. We show that for a set of quite general disjoining-conjoining pressure potentials, the free surface can adopt only five nontrivial static patterns; in particular, we find solutions when the height goes to zero which describe satisfactorily the complete free surface for a finite amount of fluid deposited on a substrate. To test the extension of the applicability of our solutions, we compare them with those obtained when the lubrication approximations are not employed and under conditions where the lubrication hypothesis are not strictly valid, and also with axisymmetric solutions. For a given disjoining-conjoining potential, we report a new analytical solution that accounts for all the five possible solutions.
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Affiliation(s)
- Carlos Alberto Perazzo
- IMeTTyB, Universidad Favaloro-CONICET, Solís 453, C1078AAI Buenos Aires, Argentina
- Departamento de Física y Química, FICEN, Universidad Favaloro, Sarmiento 1853, C1044AAA Buenos Aires, Argentina
| | - J R Mac Intyre
- Instituto de Física Arroyo Seco IFAS (UNCPBA) and CIFICEN (UNCPBA-CICPBA-CONICET), Pinto 399, 7000, Tandil, Argentina
| | - J M Gomba
- Instituto de Física Arroyo Seco IFAS (UNCPBA) and CIFICEN (UNCPBA-CICPBA-CONICET), Pinto 399, 7000, Tandil, Argentina
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Radke CJ. Film and membrane-model thermodynamics of free thin liquid films. J Colloid Interface Sci 2014; 449:462-79. [PMID: 25648681 DOI: 10.1016/j.jcis.2014.12.079] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Revised: 12/19/2014] [Accepted: 12/23/2014] [Indexed: 11/30/2022]
Abstract
In spite of over 7 decades of effort, the thermodynamics of thin free liquid films (as in emulsions and foams) lacks clarity. Following a brief review of the meaning and measurement of thin-film forces (i.e., conjoining/disjoining pressures), we offer a consistent analysis of thin-film thermodynamics. By carefully defining film reversible work, two distinct thermodynamic formalisms emerge: a film model with two zero-volume membranes each of film tension γ(f) and a membrane model with a single zero-volume membrane of membrane tension 2γ(m). In both models, detailed thermodynamic analysis gives rise to thin-film Gibbs adsorption equations that allow calculation of film and membrane tensions from measurements of disjoining-pressure isotherms. A modified Young-Laplace equation arises in the film model to calculate film-thickness profiles from the film center to the surrounding bulk meniscus. No corresponding relation exists in the membrane model. Illustrative calculations of disjoining-pressure isotherms for water are presented using square-gradient theory. We report considerable deviations from Hamaker theory for films less than about 3 nm in thickness. Such thin films are considerably more attractive than in classical Hamaker theory. Available molecular simulations reinforce this finding.
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Affiliation(s)
- C J Radke
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA 94720-1462, United States.
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Yi T, Wang Q, Lichter S. Conformations of a dipolar solute in a Stockmayer solvent channel. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:15286-15293. [PMID: 23050989 DOI: 10.1021/la303252c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
A wide range of molecules, from inorganic to biological, self-assemble on surfaces. Previous studies have elucidated many features of solute reorganization on surfaces using coarse-grained modeling, implicit solvents, and constraints such as chemically bonding the solute to the surface. Using molecular dynamics simulations under various combinations of interaction parameters, solute fractions, and solute dipole moment, we study the redistribution of freely-rotating dipolar solute molecules solvated by a water-like Stockmayer solvent initially adhered to a face-centered cubic substrate. The balance of attractive and repulsive forces is essential for acquiring a particular stable conformation. Here we show that the adsorbed molecules redistribute into different conformations--wetting film, nonwetting, partial wetting, and pseudopartial wetting drops--depending on the parameter values. We observe that the pseudopartial wetting drop is transient and its rate of spreading fluctuates, slowing to nearly zero as it passes through particular conformations before reaching an equilibrium thin film. Strong attraction between solute molecules yields a droplet with a net dipole moment. A high solute fraction leads to a pancake-like conformation arising from a balance of surface tension and van der Waals forces. This study augments our understanding of the evolution of aggregates in biological systems and also the design of polymers for self-assembled monolayers for industrial applications.
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Affiliation(s)
- Taeil Yi
- Department of Mechanical Engineering, Northwestern University, Evanston, Illinois 60208, United States.
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Yuan Q, Zhao YP. Topology-dominated dynamic wetting of the precursor chain in a hydrophilic interior corner. Proc Math Phys Eng Sci 2011. [DOI: 10.1098/rspa.2011.0305] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The topology-dominated dynamic wetting of a droplet in a hydrophilic interior corner was explored using molecular dynamics simulations and molecular kinetic theory. A wetting transition in the interior corner of a single-file water-molecule precursor chain (PC), which eliminated the stress singularity and advanced much faster than the precursor film, was controlled by the interior angle. Owing to the confinement in the interior corner, the potential surface is lower and smoother. The one-dimensional hydrogen-bond chain transferred the disjoining pressure to drive the PC to slip-like ice. As an example, a stable and long metallic monatomic chain was formed using the unique transport properties of the PC for the first time. Our results may help in understanding the topology-dominated dynamic wetting in a hydrophilic interior corner, expand ‘Taylor conjecture’ to nanoscale and develop new applications at nanoscale.
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Affiliation(s)
- Quanzi Yuan
- State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Ya-Pu Zhao
- State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
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Goicochea AG, Nahmad-Achar E, Pérez E. Colloidal stability dependence on polymer adsorption through disjoining pressure isotherms. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:3529-3537. [PMID: 19228014 DOI: 10.1021/la802585h] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The disjoining pressure of polymers confined by colloidal walls was computed using dissipative particle dynamics simulations at constant chemical potential, volume, and temperature. The polymers are able to adsorb on the surfaces according to two models. In the so-called surface-modifying polymers, all monomers composing the chains have the same affinity for the substrate, whereas for the end-grafted polymer only the monomer at one of the ends of the polymer molecule adsorbs on the colloidal surface, resembling the behavior of dispersing agents. We find that these adsorption models yield markedly different disjoining pressure isotherms, which in turn predict different stability conditions for the colloidal dispersion. Our results show that for end-grafted polymers, a larger degree of polymerization at the same monomer concentration leads to better stability than for the surface-modifying ones. But also the unbound monomers of the surface-modifying type dominate over both kinds of polymers at large surface distances. The origin of these differences when the chemical nature of monomers is the same, and molecular weight and polymer concentration are used to characterize colloidal stability, is found to be mainly entropic.
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Affiliation(s)
- A Gama Goicochea
- Centro de Investigación en Polímeros (Grupo COMEX), Marcos Achar Lobatón No. 2, Tepexpan, 55885 Acolman, Estado de México, Mexico.
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Shklyaev S, Khenner M, Alabuzhev AA. Enhanced stability of a dewetting thin liquid film in a single-frequency vibration field. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2008; 77:036320. [PMID: 18517524 DOI: 10.1103/physreve.77.036320] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2007] [Revised: 02/13/2008] [Indexed: 05/26/2023]
Abstract
Dynamics of a thin dewetting liquid film on a vertically oscillating substrate is considered. We assume moderate vibration frequency and large (compared to the mean film thickness) vibration amplitude. Using the lubrication approximation and the averaging method, we formulate the coupled sets of equations governing the pulsatile and the averaged fluid flows in the film, and then derive the nonlinear amplitude equation for the averaged film thickness. We show that there exists a window in the frequency-amplitude domain where the parametric and shear-flow instabilities of the pulsatile flow do not emerge. As a consequence, in this window the averaged description is reasonable and the amplitude equation holds. The linear and nonlinear analyses of the amplitude equation and the numerical computations show that such vibration stabilizes the film against dewetting and rupture.
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Affiliation(s)
- S Shklyaev
- Department of Theoretical Physics, Perm State University, Perm, Russia
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