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1.
We present a mesoscopic model for simulating the dynamics of a non-volatile liquid on a solid substrate. The wetting properties
of the solid can be tuned from complete wetting to total non-wetting. This model opens the way to study the dynamics of drops
and liquid thin films at mesoscopic length scales of the order of the nanometer. As particular applications, we analyze the
kinetics of spreading of a liquid drop wetting a solid substrate and the dewetting of a liquid film on a hydrophobic substrate.
In all these cases, very good agreement is found between simulations and theoretical predictions. 相似文献
2.
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. 相似文献
3.
Carvalho AJ Pereira-da-Silva MA Faria RM 《The European physical journal. E, Soft matter》2006,20(3):309-315
Self-organized block copolymer structures derived from dewetting of thin films are becoming important in nanotechnology because
of the various spontaneous and regular sub-micrometric surface patterns that may be obtained. Here, we report on the self-organization
of a poly(styrene)-b-poly(ethene-co-butene-1)-b-poly(styrene) triblock copolymer during drying of its solution over a mica
substrate. Regular submicrometric arrangements with long-range order were formed at critical polymer concentrations, consisting
of parallel ribbons and hexagonal arrays of dots (droplets). This variety of highly ordered structures is explained by the
interplay between forming mechanisms, mainly due to “fingering instabilities” at the three-phase line of the copolymer solution
during drying. The thickness of the structures was “quantized” due to the microphase separation of the block copolymer. The
formation of hexagonal patterns may be attributed to Marangoni instability at the liquid film surface prior to dewetting. 相似文献
4.
N. Rehse C. Wang M. Hund M. Geoghegan R. Magerle G. Krausch 《The European physical journal. E, Soft matter》2001,4(1):69-76
We study the wetting behaviour of thin polystyrene (PS) films on regularly corrugated silicon substrates. Below a critical
film thickness the PS films are unstable and dewet the substrates. The dewetting process leads to the formation of nanoscopic
PS channels filling the grooves of the corrugated substrates. Films thicker than the critical thickness appear stable and
follow the underlying corrugation pattern. The critical thickness is found to scale with the radius of gyration of the unperturbed
polymer chains.
Received 6 April 2000 and Received in final form 24 August 2000 相似文献
5.
Blossey R Münch A Rauscher M Wagner B 《The European physical journal. E, Soft matter》2006,20(3):267-271
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. 相似文献
6.
Xia Han Chunyan Luo Yanying Dai Honglai Liu 《Journal of Macromolecular Science: Physics》2013,52(6):1050-1061
Surface structures and compositions of poly(Styrene-block-Ethylene/Butylene-block-Styrene) (SEBS)/Poly(Methyl Methacrylate) (PMMA) blend films have been studied by Atomic Force Microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS). Substrates with different hydrophobicity and SEBS with and without Maleic Anhydride (MA) grafting were used to study the effect of polymer-substrate interactions. It is indicated that the surface energy of the substrate (substrate/air) plays a crucial role on the surface composition of the polymer component. For a fixed surface, the adsorption of polymer on the substrate is also important. The hydrophilic sites of SEBS-g-MA can prevent the dewetting of the SEBS-g-MA from the substrate. The dewetting of PMMA from the SEBS-g-MA will make the PMMA protrusions more pronounced, and the SEBS-g-MA phase domains are enlarged after annealing treatment. An adsorption scheme is suggested to explain the phase inversion and height difference observed in the various polymers used. In addition, SEBS triblock copolymers form wormlike and meshlike microphase separation morphologies on the hydrophilic and hydrophobic substrates, respectively. 相似文献
7.
《Journal of Macromolecular Science: Physics》2013,52(3-4):611-620
Crystallization of poly(ethylene oxide) (PEO) in thin films was studied using hot-stage polarized optical microscopy. Isothermal linear crystal growth rates were measured for various film thicknesses at various degrees of undercooling. At a given crystallization temperature, the linear crystal growth rate decreased exponentially with decreasing film thickness below a film thickness of 80 nm. Films showed similar spherulitic morphology down to a film thickness of 30 nm. Control experiments on hydrophilic and hydrophobic surfaces showed that surface chemistry affects stability of the polymer films and causes a competition between crystallization and dewetting. 相似文献
8.
The spatial confinement of a fluctuation spectrum leads to forces at the confining boundaries. While electromagnetic (EM)
fluctuations lead to the well-known dispersion forces, the acoustic analogy has widely been neglected. We show that the strength
of the forces resulting from confined acoustic modes may be of the same order of magnitude as van der Waals forces. Additionally,
the predicted scaling behavior is identical to the non-retarded case of the EM fluctuations. Our results suggest that dewetting
experiments using polymer films are strongly influenced by the acoustic dispersion forces.
Received 5 March 2002 and Received in final form 21 May 2002 相似文献
9.
Melissa A. Holmes Michael E. Mackay Rachel K. Giunta 《Journal of nanoparticle research》2007,9(5):753-763
Addition of fullerenes (C60 or buckyballs) to a linear polymer has been found to eliminate dewetting when a thin (∼50 nm) film is exposed to solvent
vapor. Based on neutron reflectivity measurements, it is found that the fullerenes form a coherent layer approximately 2 nm
thick at the substrate – polymer film interface during the spin-coating process. The thickness and relative fullerene concentration
(∼29 vol%) is not altered during solvent vapor annealing and it is thought this layer forms a solid-like buffer shielding
the adverse van der Waals forces promoted by the underlying substrate. Several polymer films produced by spin- or spray-coating
were tested on both silicon wafers and live surface acoustic wave sensors demonstrating fullerenes stabilize many different
polymer types, prepared by different procedures and on various surfaces. Further, the fullerenes drastically improve sensor
performance since dewetted films produce a sensor that is effectively inoperable. 相似文献
10.
Al Akhrass S Reiter G Hou SY Yang MH Chang YL Chang FC Wang CF Yang AC 《Physical review letters》2008,100(17):178301
A nonmonotonic, two-stage dewetting behavior was observed for spin coated thin viscoelastic polymer films on soft elastic substrates. At times shorter than the relaxation time of the polymer (ttau_{rep}), dewetting accelerated, accompanied by an unstable rim. However, holes nucleated at t相似文献
11.
Higgins AM Sferrazza M Jones RA Jukes PC Sharp JS Dryden LE Webster J 《The European physical journal. E, Soft matter》2002,8(2):137-143
We investigate the dynamics of spinodal dewetting in liquid-liquid polymer systems. Dewetting of poly(methyl-methacrylate)
(PMMA) thin films on polystyrene (PS) “substrates” is followed in situ using neutron reflectivity. By following the development of roughness at the PS/PMMA interface and the PMMA surface we extract
characteristic growth times for the dewetting process. These characteristic growth times are measured as a function of the
molecular weight of the two polymers. By also carrying out experiments in the regime where the dynamics are independent of
the PS molecular weight, we are able to use dewetting to probe the scaling of the PMMA thin film viscosity with temperature
and molecular weight. We find that this scaling reflects bulk behaviour. However, absolute values are low compared to bulk
viscosities, which we suggest may be due in part to slippage at the polymer/polymer interface.
Received 25 June 2001 and Received in final form 5 December 2001 相似文献
12.
The substrate is shown to induce substantial ordering in diblock copolymer thin films above the bulk order-disorder transition
(ODT) where, thermodynamically, a phase mixed state is favored. Initially, uniform films reorganize to form a hierarchy of
transient surface patterns and stable film thicknesses that depend on the initial film thickness and on the substrate. Self-consistent
field calculations of the free energy of the system for different situations, depending on the relative tendency for the different
block components to be attracted to the substrate and/or free surface, provide an explanation of the formation of the stable
film thicknesses. A continuum picture proposed earlier by Brochard et al.rovides an explanation of the wetting characteristics of this system. In some cases the ordering destabilizes the film so
that dewetting occurs (wetting autophobicity), whereas in other cases the surface ordering results in a kinetic stabilization
of a film that would otherwise dewet.
Received 3 August 2001 and Received in final form 1 November 2001 相似文献
13.
L. Fleischmann J. Bonn B. Bornschein P. Leiderer E.W. Otten M. Przyrembel Ch. Weinheimer 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(3):521-529
The dewetting dynamics of solid films of hydrogen isotopes, quench-condensed on a graphite substrate, was measured at various
temperatures below desorption by observing the stray light from the film. A schematic model describing the dewetting process
by surface diffusion is presented, which agrees qualitatively with our data. The activation energies of different hydrogen
isotopes for surface diffusion were determined. The time constant for dewetting of a quench-condensed film at the working temperature of 1.86 K of the mainz neutrino mass experiment was extrapolated.
Received 30 December 1999 相似文献
14.
《Comptes Rendus Physique》2013,14(7):553-563
We review some models for the dynamics of dewetting of ultra-thin solid films. We discuss the similarities and the differences between faceted and non-faceted systems. The faceting of the dewetting rim leads to corrections in the velocity of dewetting fronts both in flat and axisymmetric geometries. The faceting of the edge of the dewetting rim leads to a strong anisotropy of the dewetting instability. Faceting also induces novel dewetting regimes such as layer-by-layer dewetting, and monolayer dewetting. 相似文献
15.
Surface damage produced by single MeV-GeV heavy ions impacting ultrathin polymer films has been shown to be weaker than those observed under bulk (thick film) conditions. The decrease in damage efficiency has been attributed to the suppression of long-range effects arising from excited atoms lying deeply in the solid. This raises the possibility that the substrate of the films itself is relevant to the radiation effects seen at the top surface. Here, the role of the substrate on cratering induced by individual 1.1 GeV Au ions in ultrathin poly(methyl methacrylate) (PMMA) layers is investigated. Materials of different thermal and electrical properties (Si, SiO2, and Au) are used as substrates to deposit PMMA thin films of various thicknesses from ∼1 to ∼300 nm. We show that in films thinner than ∼40 nm craters are modulated by the underlying substrate to a degree that depends on the transport properties of the medium. Crater size in ultrathin films deposited on the insulating SiO2 is larger than in similar films deposited on the conducting Au layer. This is consistent with an inefficient coupling of the electronic excitation energy to the atomic cores in metals. On the other hand, the damage on films deposited on SiO2 is not very different from the Si substrate with a native oxide layer, suggesting, in addition, poor energy transmission across the film/substrate interface. The experimental observations are also compared to calculations from an analytical model based on energy addition and transport from the excited ion track, which describe only partially the results. 相似文献
16.
Nanoimprint texturing of transparent flexible substrates for improved light management in thin‐film solar cells
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Karen Wilken Ulrich W. Paetzold Matthias Meier Nicole Prager Matthias Fahland Friedhelm Finger Vladimir Smirnov 《固体物理学:研究快报》2015,9(4):215-219
We present a nanoimprint based approach to achieve efficient light management for solar cells on low temperature transparent polymer films. These films are particularly low‐priced, though sensitive to temperature, and therefore limiting the range of deposition temperatures of subsequent solar cell layers. By using nanoimprint technology, we successfully replicated optimized light trapping textures of etched high temperature ZnO:Al on a low temperature PET film without deterioration of optical properties of the substrate. The imprint‐textured PET substrates show excellent light scattering properties and lead to significantly improved incoupling and trapping of light in the solar cell, resulting in a current density of 12.9 mA/cm2, similar to that on a glass substrate. An overall efficiency of 6.9% was achieved for a flexible thin‐film silicon solar cell on low cost PET substrate. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
17.
G. Reiter S. Al Akhrass M. Hamieh P. Damman S. Gabriele T. Vilmin E. Rapha?l 《The European physical journal. Special topics》2009,166(1):165-172
Employing mass conservation, time-resolved dewetting experiments of thin polymer films allow to determine in real time the
dynamic contact angle and the slippage length. Moreover, based on a systematic variation of interfacial properties of a polymer
brush, dewetting makes it possible to calculate the force it needs to extract a single polymer chain from its own melt.
In the visco-elastic regime close to the glass transition, the temperature and molecular weight dependence of the relaxation
time of residual stresses resulting from film preparation by spin-coating can be obtained from the evolution of the shape
of the dewetting rim.
The presented examples demonstrate that dewetting represents a powerful approach for a sensitive characterization of rheological,
frictional and interfacial properties of thin polymer films. 相似文献
18.
对存在壁面滑移的含非溶性表面活性剂薄液膜在固体表面的去湿过程,采用PDECOL程序对描述其演化过程的液膜厚度和表面活性剂浓度方程组进行数值求解.基于液膜表面扰动波形的变化,分析各参数对去湿特性及液膜稳定性的影响规律.研究指出:Marangoni数M较小时其效应使液膜失稳区缩短,而M较大时液膜失稳区间无限延伸,稳定性降低;毛细力数减小使液膜失稳区间缩短,减至一定程度后可有效抑制去湿现象的发生;滑移效应对演化过程的影响与M有关,M较小时滑移使液膜失稳区间缩减,使扰动增长率增大,M较大时这一影响并不显著;随平衡液膜厚度增大,液膜表面的扰动程度减小,但扰动区间显著增大.相对于外源性表面活性剂而言,内源性情形的失稳区间更小,液膜稳定性更强. 相似文献
19.
Perovskites thin films with the composition La0.6Ca0.4MnO3 doped with 20% Fe, were prepared by pulsed reactive crossed beam laser ablation, where a synchronized reaction gas pulse interacts with the ablation plume. The films were grown on various substrates and the highest colossal magnetoresistance ratio (CMR) was detected by Hall measurements for films grown on LaAlO3 (1 0 0), which was selected as substrate for further investigations.Several growth parameters, such as substrate temperature and target to substrate distance were varied to analyze their influence on the film properties.The structure of the deposited thin films was characterized by X-ray diffraction and atomic force microscope, while Rutherford backscattering (RBS) was used to determine the film stoichiometry. The electrical properties were determined by Hall effect measurements in a magnetic field of 0.51 T.These measurements reveal that the amplitude of the CMR ratio depends strongly on the substrate and that the oxygen content influences the temperature where the transition from semiconductor to metal is observed. 相似文献
20.
Ultra thin films of glassy polymers such as polystyrene (PS) can show a) anomalously large thickness changes, b) unexpected
dewetting properties, c) large shifts in the glass temperature Tg. The present discussion focusses mainly on point a). A certain cascade of metastable states is presented together with (tentative)
explanations.
Received 1 March 2001 and Received in final form 10 May 2001 相似文献