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Martínez-Calvo A, Moreno-Boza D, Sevilla A. Non-linear dynamics and self-similarity in the rupture of ultra-thin viscoelastic liquid coatings. SOFT MATTER 2021; 17:4363-4374. [PMID: 33908465 DOI: 10.1039/d0sm02204g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The influence of viscoelasticity on the dewetting of ultrathin polymer films is unraveled by means of theory and numerical simulations in the inertialess limit. Three viscoelastic models are employed to analyse the dynamics of the film, namely the Oldroyd-B, Giesekus, and FENE-P models. We revisit the linear stability analysis first derived by [Tomar et al., Eur. Phys. J. E., 2006, 20, 185-200] for a Jeffrey's film to conclude that all three models formally share the same dispersion relation. For times close to the rupture singularity, the self-similar regime recently discovered [Moreno-Boza et al., Phys. Rev. Fluids, 2020, 5, 014002], where the dimensionless minimum film thickness scales with the dimensionless time until rupture as hmin = 0.665τ1/3, is asymptotically established independently of the rheological model. The spatial structure of the flow is characterised by a Newtonian core and a thin viscoelastic boundary layer at the free surface, where polymeric stresses become singular as τ → 0. The Deborah number and the solvent-to-total viscosity ratio affect the rupture time but not the length scale of the resulting dewetting pattern and asymptotic flow structure close to rupture, which is thus shown to be universal. Our three-dimensional simulations lead us to conclude that bulk viscoelasticity alone does not explain the experimental observations of dewetting of polymeric films near the glass transition.
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Affiliation(s)
- A Martínez-Calvo
- Grupo de Mecánica de Fluidos, Universidad Carlos III de Madrid, Av. Universidad 30, 28911 Leganés (Madrid), Spain.
| | - D Moreno-Boza
- Grupo de Mecánica de Fluidos, Universidad Carlos III de Madrid, Av. Universidad 30, 28911 Leganés (Madrid), Spain.
| | - A Sevilla
- Grupo de Mecánica de Fluidos, Universidad Carlos III de Madrid, Av. Universidad 30, 28911 Leganés (Madrid), Spain.
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2
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Russell TP, Chai Y. 50th Anniversary Perspective: Putting the Squeeze on Polymers: A Perspective on Polymer Thin Films and Interfaces. Macromolecules 2017. [DOI: 10.1021/acs.macromol.7b00418] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Affiliation(s)
- Thomas P. Russell
- Polymer
Science and Engineering Department, University of Massachusetts Amherst, Amherst, Massachusetts 01003, United States
- Materials
Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, United States
- Beijing
Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China
| | - Yu Chai
- Materials
Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, United States
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3
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Mukherjee R, Sharma A. Instability, self-organization and pattern formation in thin soft films. SOFT MATTER 2015; 11:8717-8740. [PMID: 26412507 DOI: 10.1039/c5sm01724f] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The free surface of a thin soft polymer film is often found to become unstable and self-organizes into various meso-scale structures. In this article we classify the instability of a thin polymer film into three broad categories, which are: category 1: instability of an ultra-thin (<100 nm) viscous film engendered by amplification of thermally excited surface capillary waves due to interfacial dispersive van der Waals forces; category 2: instability arising from the attractive inter-surface interactions between the free surface of a soft film exhibiting room temperature elasticity and another rigid surface in its contact proximity; and category 3: instability caused by an externally applied field such as an electric field or a thermal gradient, observed in both viscous and elastic films. We review the salient features of each instability class and highlight how characteristic length scales, feature morphologies, evolution pathways, etc. depend on initial properties such as film thickness, visco-elasticity (rheology), residual stress, and film preparation conditions. We emphasize various possible strategies for aligning and ordering of the otherwise isotropic structures by combining the essential concepts of bottom-up and top-down approaches. A perspective, including a possible future direction of research, novelty and limitations of the methods, particularly in comparison to the existing patterning techniques, is also presented for each setting.
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Affiliation(s)
- Rabibrata Mukherjee
- Instability and Soft Patterning Laboratory, Department of Chemical Engineering, Indian Institute of Technology, Kharagpur, 721 302, India.
| | - Ashutosh Sharma
- Department of Chemical Engineering and Nano-science Center, Indian Institute of Technology, Kanpur, 208016, India.
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5
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Backholm M, Benzaquen M, Salez T, Raphaël E, Dalnoki-Veress K. Capillary levelling of a cylindrical hole in a viscous film. SOFT MATTER 2014; 10:2550-2558. [PMID: 24647857 DOI: 10.1039/c3sm52940a] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The capillary levelling of cylindrical holes in viscous polystyrene films was studied using atomic force microscopy as well as quantitative analytical scaling arguments based on thin film theory and self-similarity. The relaxation of the holes was shown to consist of two different time regimes: an early regime where opposing sides of the hole do not interact, and a late regime where the hole is filling up. For the latter, the self-similar asymptotic profile was derived analytically and shown to be in excellent agreement with experimental data. Finally, a binary system of two holes in close proximity was investigated where the individual holes fill up at early times and coalesce at longer times.
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Affiliation(s)
- Matilda Backholm
- Department of Physics & Astronomy and the Brockhouse Institute for Materials Research, McMaster University, Hamilton, Canada.
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6
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de Silva JP, Cousin F, Wildes AR, Geoghegan M, Sferrazza M. Symmetric and asymmetric instability of buried polymer interfaces. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2012; 86:032801. [PMID: 23030968 DOI: 10.1103/physreve.86.032801] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2012] [Indexed: 06/01/2023]
Abstract
We demonstrate using neutron reflectometry that the internal interfaces in a trilayer system of two identical thick polystyrene layers sandwiching a much thinner (deuterated) poly(methyl methacrylate) layer 15 nm thick (viscosity matched with the polystyrene layers) increase in roughness at the same rate. When the lower polystyrene layer is replaced with a layer of the same polymer of much greater molecular mass, two different growths of the interfaces are observed. From the growth of the interface for this asymmetric case in the solid regime using the theoretical prediction of the spinodal instability including slippage at the interface, a value of the Hamaker constant of the system has been extracted in agreement with the calculated value. For the symmetric case the rise time of the instability is much faster.
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Affiliation(s)
- J P de Silva
- Departement de Physique, Faculté des Sciences, Université Libre de Bruxelles, CP223 Boulevard du Triomphe, 1050 Brussels, Belgium
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7
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Snoeijer JH, Eggers J. Asymptotic analysis of the dewetting rim. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2010; 82:056314. [PMID: 21230583 DOI: 10.1103/physreve.82.056314] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2010] [Revised: 09/21/2010] [Indexed: 05/30/2023]
Abstract
Consider a film of viscous liquid covering a solid surface, which it does not wet. If there is an initial hole in the film, the film will retract further, forming a rim of fluid at the receding front. We calculate the shape of the rim as well as the speed of the front using lubrication theory. We employ asymptotic matching between the contact line region, the rim, and the film. Our results are consistent with simple ideas involving dynamic contact angles and permit us to calculate all free parameters of this description, previously unknown.
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Affiliation(s)
- Jacco H Snoeijer
- Physics of Fluids Group and J. M. Burgers Centre for Fluid Dynamics, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
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8
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Ziebert F, Raphaël E. Dewetting dynamics of stressed viscoelastic thin polymer films. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2009; 79:031605. [PMID: 19391952 DOI: 10.1103/physreve.79.031605] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2008] [Indexed: 05/27/2023]
Abstract
Ultrathin polymer films that are produced, e.g., by spin coating are believed to be stressed since polymers are "frozen in" into out-of-equilibrium configurations during this process. In the framework of a viscoelastic thin-film model, we study the effects of lateral residual stresses on the dewetting dynamics of the film. The temporal evolution of the height profiles and the velocity profiles inside the film as well as the dissipation mechanisms are investigated in detail. Both the shape of the profiles and the importance of frictional dissipation vs viscous dissipation inside the film are found to change in the course of dewetting. The interplay of the nonstationary profiles, the relaxing initial stress, and the changes in the dominance of the two dissipation mechanisms caused by nonlinear friction with the substrate is responsible for the rich behavior of the system. In particular, our analysis sheds a different light on the occurrence of the unexpected maximum in the rim width obtained recently in experiments on polystyrene-polydimethylsiloxane systems.
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Affiliation(s)
- Falko Ziebert
- Laboratoire de Physico-Chimie Théorique-UMR CNRS Gulliver 7083, ESPCI, 10 rue Vauquelin, F-75231 Paris, France
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9
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Affiliation(s)
- S. Joon Kwon
- Nano Science and Technology Division, Korea Institute of Science and Technology, P.O. Box 131, Cheongryang, Seoul, 130-650, Korea
| | - Jae-Gwan Park
- Nano Science and Technology Division, Korea Institute of Science and Technology, P.O. Box 131, Cheongryang, Seoul, 130-650, Korea
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11
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Vilmin T, Raphaël E. Dewetting of thin polymer films. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2006; 21:161-74. [PMID: 17146593 DOI: 10.1140/epje/i2006-10057-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2006] [Accepted: 11/09/2006] [Indexed: 05/12/2023]
Abstract
We study the dewetting of thin polymer films deposited on slippery substrate. Recent experiments on these systems have revealed many unexpected features. We develop here a model that takes into account the rheological properties of polymer melts, focussing on two dewetting geometries (the receding of a straight edge, and the opening of a hole). We show that the friction law associated with the slippage between the film and the substrate has a direct influence on the dewetting dynamic. In addition, we demonstrate that residual stresses, which can be stored in the films due to their viscoelasticity, are a source of destabilization for polymer films, and accelerate the dewetting process.
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Affiliation(s)
- T Vilmin
- Laboratoire de Physico-Chimie Théorique, UMR CNRS 7083, ESPCI, 10 rue Vauquelin, 75231, Paris Cedex 05, France.
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12
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Blossey R, Münch A, Rauscher M, Wagner B. Slip vs. viscoelasticity in dewetting thin films. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2006; 20:267-71. [PMID: 16794776 DOI: 10.1140/epje/i2006-10018-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2006] [Accepted: 06/06/2006] [Indexed: 05/10/2023]
Abstract
Ultrathin polymer films on non-wettable substrates display dynamic features which have been attributed to either viscoelastic or slip effects. Here we show that in the weak- and strong-slip regime, effects of viscoelastic relaxation are either absent or essentially indistinguishable from slip effects. Strong slip modifies the fastest unstable mode in a rupturing thin film, which questions the standard approach to reconstruct the effective interface potential from dewetting experiments.
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Affiliation(s)
- R Blossey
- Biological Nanosystems, Interdisciplinary Research Institute, c/o IEMN Avenue Poincaré, BP 60069, F-59652, Villeneuve d'Ascq, France.
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13
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Yang MH, Hou SY, Chang YL, Yang ACM. Molecular recoiling in polymer thin film dewetting. PHYSICAL REVIEW LETTERS 2006; 96:066105. [PMID: 16606016 DOI: 10.1103/physrevlett.96.066105] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2005] [Indexed: 05/08/2023]
Abstract
The molecular recoiling force stemming from nonequilibrium chain conformation was found to play a very important role in the dewetting stability of polymer thin films. Correct measurements and inclusion of this molecular force into thermodynamic consideration are crucial for analyzing dewetting phenomena and nanoscale polymer chain physics. This force was measured using a simple method based on contour relaxation at the incipient dewetting holes. The recoiling stress was found to increase dramatically with molecular weight and decreasing film thickness. The corresponding forces were calculated to be in the range from 9.0 to 28.2 mN/m, too large to be neglected when compared to the dispersive forces (approximately 10 mN/m) commonly operative in thin polymer films.
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Affiliation(s)
- M H Yang
- Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu, Taiwan
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14
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Bodiguel H, Fretigny C. Viscoelastic dewetting of a polymer film on a liquid substrate. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2006; 19:185-93. [PMID: 16491310 DOI: 10.1140/epje/e2006-00021-8] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2005] [Indexed: 05/06/2023]
Abstract
The Dewetting of thin polymer films (60-300 nm) on a non-wettable liquid substrate has been studied in the vicinity of their glass transition temperature. In our experiment, we observe a global contraction of the film while its thickness remains uniform. We show that, in this case, the strain corresponds to simple extension, and we verify that it is linear with the stress applied by the surface tension. This allows direct measurement of the stress/strain response as a function of time, and thus permits the measurement of an effective compliance of the thin films. It is, however, difficult to obtain a complete viscoelastic characterization, as the short time response is highly dependant on the physical age of the sample. Experimental results underline the effects of residual stress and friction when dewetting is analyzed on rigid substrates.
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Affiliation(s)
- H Bodiguel
- ESPCI, Laboratoire de Physico-Chimie des Polymères et des Milieux Dispersés, CNRS UMR 7615, 10 rue Vauquelin, 75231, Paris Cedex 05, France
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15
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Qin S, Wei D, Liao Q, Jin X. Dewetting Process of Polyelectrolyte Multilayer Films in Hot Water. Macromol Rapid Commun 2006. [DOI: 10.1002/marc.200500620] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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16
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Gabriele S, Damman P, Sclavons S, Desprez S, Coppée S, Reiter G, Hamieh M, Akhrass SA, Vilmin T, Raphaël E. Viscoelastic dewetting of constrained polymer thin films. ACTA ACUST UNITED AC 2006. [DOI: 10.1002/polb.20919] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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17
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18
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Reiter G, Hamieh M, Damman P, Sclavons S, Gabriele S, Vilmin T, Raphaël E. Residual stresses in thin polymer films cause rupture and dominate early stages of dewetting. NATURE MATERIALS 2005; 4:754-8. [PMID: 16184173 DOI: 10.1038/nmat1484] [Citation(s) in RCA: 227] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2005] [Accepted: 08/11/2005] [Indexed: 05/04/2023]
Abstract
In attempting to reduce the size of functional devices, the thickness of polymer films has reached values even smaller than the diameter of the unperturbed molecule. However, despite enormous efforts for more than a decade, our understanding of the origin of some puzzling properties of such thin films is still not satisfactory and several peculiar observations remain mysterious. For example, under certain conditions, such films show negative expansion coefficients or show undesirable rupture although energetically they are expected to be stable. Here, we demonstrate that many of these extraordinary effects can be related to residual stresses within the film, resulting from the preparation of these films from solution by fast evaporation of the solvent. Consequently, depending on thermal history and ageing time, such films show significant changes even in the glassy state, which we quantify by dewetting experiments and corresponding theoretical studies. Identifying the relevance of frozen-in polymer conformations gives us a handle for manipulating and controlling properties of nanometric thin polymer films.
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Affiliation(s)
- Günter Reiter
- Institut de Chimie des Surfaces et Interfaces, CNRS-UHA, 15, rue Jean Starcky, BP 2488, 68057 Mulhouse Cedex, France.
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19
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Ondarçuhu T, Piednoir A. Pinning of a contact line on nanometric steps during the dewetting of a terraced substrate. NANO LETTERS 2005; 5:1744-50. [PMID: 16159217 DOI: 10.1021/nl051093r] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
We study the dewetting of polystyrene films on an alumina surface. We show that the morphology of dewetting holes is drastically modified by the nanometric steps on the surface. Nevertheless, below a critical step height of the order of the polymer chain dimension, the contact line is not anymore sensitive to the defects. This method thus gives an estimation of the limit of validity of macroscopic descriptions of wetting when going down to molecular dimensions.
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Affiliation(s)
- Thierry Ondarçuhu
- Nanosciences Group, CEMES-CNRS, 29 rue Jeanne Marvig, 31055 Toulouse Cedex 4, France.
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20
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Roth CB, Dutcher JR. Hole growth in freely standing polystyrene films probed using a differential pressure experiment. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2005; 72:021803. [PMID: 16196593 DOI: 10.1103/physreve.72.021803] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2004] [Revised: 04/19/2005] [Indexed: 05/04/2023]
Abstract
We have probed the whole chain mobility of polymer molecules confined to freely standing films by measuring the flow of gas through holes growing in the films at elevated temperatures using a differential pressure experiment. Freely standing polystyrene films were measured for the temperature range 92 degrees C<T<105 degrees C for films with two different molecular weights Mw=717 x 10(3) and 2240 x 10(3) , with thicknesses 51 nm<h<97 nm . This range of film thicknesses is of particular interest because large reductions in the glass transition temperature Tg have been measured previously for freely standing PS films in this thickness range. We find that hole formation and growth, and therefore substantial chain mobility, does not occur until temperatures close to the bulk value of the glass transition temperature T(bulk)g. The characteristic growth times tau for the thinnest films, which have reduced values of Tg, are not substantially less than those for thicker films, and we find that these small differences in tau can be understood in terms of the bulk phenomenon of shear thinning. We also show that the viscosity at the edge of the hole inferred from the characteristic growth times obtained in this and previous studies exhibit shear thinning with reduced shear strain rates beta that span twelve orders of magnitude.
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Affiliation(s)
- C B Roth
- Department of Physics and the Guelph-Waterloo Physics Institute, University of Guelph, Guelph, Ontario, Canada N1G 2W1
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21
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Rauscher M, Münch A, Wagner B, Blossey R. A thin-film equation for viscoelastic liquids of Jeffreys type. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2005; 17:373-9. [PMID: 15999230 DOI: 10.1140/epje/i2005-10016-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2005] [Accepted: 05/04/2005] [Indexed: 05/03/2023]
Abstract
We derive a novel thin-film equation for linear viscoelastic media describable by generalized Maxwell or Jeffreys models. As a first application of this equation we discuss the shape of a liquid rim near a dewetting front. Although the dynamics of the liquid is equivalent to that of a phenomenological model recently proposed by Herminghaus et al. (S. Herminghaus, R. Seemann, K. Jacobs, Phys. Rev. Lett. 89, 056101 (2002)), the liquid rim profile in our model always shows oscillatory behaviour, contrary to that obtained in the former. This difference in behaviour is attributed to a different treatment of slip in both models.
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Affiliation(s)
- M Rauscher
- Max-Planck-Institut für Metallforschung, Stuttgart, Germany
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22
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Xavier JH, Pu Y, Li C, Rafailovich MH, Sokolov J. Transition of Linear to Exponential Hole Growth Modes in Thin Free-Standing Polymer Films. Macromolecules 2004. [DOI: 10.1021/ma034999x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- J. H. Xavier
- Department of Materials Science and Engineering, State University of New York at Stony Brook, Stony Brook, New York 11794-2275
| | - Y. Pu
- Department of Materials Science and Engineering, State University of New York at Stony Brook, Stony Brook, New York 11794-2275
| | - C. Li
- Department of Materials Science and Engineering, State University of New York at Stony Brook, Stony Brook, New York 11794-2275
| | - M. H. Rafailovich
- Department of Materials Science and Engineering, State University of New York at Stony Brook, Stony Brook, New York 11794-2275
| | - J. Sokolov
- Department of Materials Science and Engineering, State University of New York at Stony Brook, Stony Brook, New York 11794-2275
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23
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Damman P, Baudelet N, Reiter G. Dewetting near the glass transition: transition from a capillary force dominated to a dissipation dominated regime. PHYSICAL REVIEW LETTERS 2003; 91:216101. [PMID: 14683320 DOI: 10.1103/physrevlett.91.216101] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2003] [Indexed: 05/24/2023]
Abstract
Dynamics and corresponding morphology of dewetting of thin polystyrene films at temperatures close to the glass transition were investigated by measuring simultaneously dewetted distance and width of the rim. Comparing the opening of cylindrical holes with the retraction of a straight contact line revealed (i). a drastic influence of the geometry (planar or radial symmetry) on the dynamics at early stages, (ii). a new logarithmic dewetting regime, and (iii). transitions between four dewetting regimes clearly indicated by changes in the shape of the rim. The complete dewetting scenario can be understood as an initial dominance of capillary driving forces, which is progressively overtaken by dissipation related to the increasing size of the rim.
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Affiliation(s)
- Pascal Damman
- Laboratoire de Physicochimie des Polymeres, Université de Mons Hainaut, 20, Place du Parc, B-7000 Mons, Belgium.
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24
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Reiter G, Sferrazza M, Damman P. Dewetting of thin polymer films at temperatures close to the glass transition. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2003; 12:133-138. [PMID: 15007690 DOI: 10.1140/epje/i2003-10031-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We present detailed studies on dewetting of thin polystyrene (PS) films which were deposited onto silicon wafers coated with a polydimethylsiloxane (PDMS) monolayer. Experiments were performed at temperatures close to the glass transition temperature of PS. Several significant deviations from the dewetting behaviour of Newtonian liquids were observed. The length of the PS molecules, and thus the viscosity, turned out to be of minor importance in determining the dewetting velocity, in particular for the later regimes. In stark contrast, the geometry of the drying spot had a striking influence on the dewetting velocity. Initially, dewetting from straight contact lines proceeded faster than the opening of circular holes. At later stages, the process slowed down significantly in both cases. Under the conditions at which our experiments were performed, PS cannot flow like a simple liquid. Thus, the observed dewetting has to be the consequence of plastic deformation induced by capillary forces. Our results indicate that under such conditions the energy dissipation process is strongly affected by geometry, which is not the case for viscous liquids.
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Affiliation(s)
- G Reiter
- Institut de Chimie des Surfaces et Interfaces, CNRS-UHA, 15, rue Jean Starcky, B.P. 2488, 68057, Mulhouse Cedex, France.
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25
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Herminghaus S, Jacobs K, Seemann R. Viscoelastic dynamics of polymer thin films and surfaces. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2003; 12:101-110. [PMID: 15007686 DOI: 10.1140/epje/i2003-10044-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The strain relaxation behavior in a viscoelastic material, such as a polymer melt, may be strongly affected by the proximity of a free surface or mobile interface. In this paper, the viscoelastic surface modes of the material are discussed with respect to their possible influence on the freezing temperature and dewetting morphology of thin polymer films. In particular, the mode spectrum is connected with mode coupling theory assuming memory effects in the melt. Based on the idea that the polymer freezes due to these memory effects, surface melting is predicted. As a consequence, the substantial shift of the glass transition temperature of thin polymer films with respect to the bulk is naturally explanied. The experimental findings of several independent groups can be accounted for quantitatively, with the elastic modulus at the glass transition temperature as the only fitting parameter. Finally, a simple model is put forward which accounts for the occurrence of certain generic dewetting morphologies in thin liquid polymer films. It demonstrates that by taking into account the viscoelastic properties of the film, a morphological phase diagram may be derived which describes the observed structures of dewetting fronts. It is demonstrated that dewetting morphologies may also serve to determine nanoscale rheological properties of liquids.
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Affiliation(s)
- S Herminghaus
- Applied Physics Department, University of Ulm, D-89069, Ulm, Germany.
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26
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Saulnier F, Raphaël E, De Gennes PG. Dewetting of thin-film polymers. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2002; 66:061607. [PMID: 12513297 DOI: 10.1103/physreve.66.061607] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2002] [Indexed: 05/24/2023]
Abstract
In this paper we present a theoretical model for the dewetting of ultrathin polymer films. Assuming that the shear-thinning properties of these films can be described by a Cross-type constitutive equation, we analyze the front morphology of the dewetting film, and characterize the time evolution of the dry region radius, and of the rim height. Different regimes of growth are expected, depending on the initial film thickness, and on the power-law index involved in the constitutive equation. In the thin-films regime, the dry radius and the rim height obey power-law time dependences. We then compare our predictions with the experimental results obtained by Debrégeas et al. [Phys. Rev. Lett. 75, 3886 (1995)] and by Reiter [Phys. Rev. Lett. 87, 186101 (2001)].
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Affiliation(s)
- F Saulnier
- Laboratoire de Physique de la Matière Condensée, CNRS UMR 7125, Collège de France, 11 place Marcelin Berthelot, 75231 Paris Cedex 05, France.
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Herminghaus S, Seemann R, Jacobs K. Generic morphologies of viscoelastic dewetting fronts. PHYSICAL REVIEW LETTERS 2002; 89:056101. [PMID: 12144452 DOI: 10.1103/physrevlett.89.056101] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2002] [Indexed: 05/23/2023]
Abstract
A simple model is put forward which accounts for the occurrence of certain generic dewetting morphologies in thin liquid coatings. It demonstrates that, by taking into account the elastic properties of the coating, a morphological phase diagram may be derived which describes the observed structures of dewetting fronts. It is demonstrated that dewetting morphologies may also serve to determine nanoscale rheological properties of liquids.
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Shenoy V, Sharma A. Dewetting of glassy polymer films. PHYSICAL REVIEW LETTERS 2002; 88:236101. [PMID: 12059380 DOI: 10.1103/physrevlett.88.236101] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2002] [Indexed: 05/23/2023]
Abstract
Dynamics and morphology of hole growth in a film of power hardening viscoplastic solid [ yield stress approximately (strain-rate)(n)] is investigated. At short times the growth is exponential and depends on the initial hole size. At long times, for n>1 / 3, the growth is again exponential but with a different exponent. However, for n<1 / 3 the hole growth slows and the hole radius approaches an asymptotic value at long times. The rim shape is highly asymmetric, the height of which has a power law dependence on the hole radius (exponent close to unity for 0.25<n<0.4). The above results explain recent intriguing experiments of Reiter [Phys. Rev. Lett., 87, 186 101 (2001)] on dewetting.
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Affiliation(s)
- Vijay Shenoy
- Materials Research Centre, Indian Institute of Science, Bangalore 560 012, India.
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