Direct stress measurements in thin polymer films

Thomas, Kerrie L.; Steiner, Ullrich

doi:10.1039/c1sm05634d

Cited by 29 publications

(35 citation statements)

References 37 publications

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“…In many cases, the thickness of these films was less than the unperturbed size of the polymer chain (represented by the radius of gyration), which may explain the deviations from the behavior observed in polymer bulk samples . On the other hand, several authors proposed that films prepared by spin‐coating consist of polymer chains in out‐of‐equilibrium conformations, which cause residual stresses within these films . Along with studies on T g , several rheological probes have been developed for the investigation of mechanical properties of thin polymer films, especially, dewetting, wrinkling, electrohydrodynamic instability, nanobubble inflation, and capillary levelling have been used successfully for studying polymer films.…”

Section: Introductionmentioning

confidence: 99%

Relaxing nonequilibrated polymers in thin films at temperatures slightly above the glass transition

Chowdhury

Akhrass

Ziebert

et al. 2017

J Polym Sci B Polym Phys

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We have studied the dewetting process of thin polystyrene films on nonwettable substrates in the viscoelastic regime slightly above the glass transition temperature. The evolution of the shape of the dewetting rim for varying film thickness, molecular weights and dewetting temperatures allowed us to determine the relaxation rates of residual stresses, which originated from nonequilibrated polymer chain conformations formed during film preparation by spin-coating. For long chain polymers, we found rates notably faster than the longest bulk relaxation processes, highly independent of molecular weight and temperature. Our study demonstrates that dewetting is a powerful tool for sensitive characterization of nonequilibrium properties of thin polymer films. FIGURE 3 Variation of (a) the time (s W ) when the width of the rim reached a maximum value and (b) maximum dewetting velocity (V M ) with film thicknesses for films of different molecular weight PS dewetting at various temperatures close to the glass transition, as indicated in the graphs. Black and red lines represent guides to the eyes having the corresponding thickness dependences s W $ h 3 0 and V M $ h 23 0 , respectively. [Color figure can be viewed at wileyonlinelibrary.com]

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Section: Introductionmentioning

confidence: 99%

Relaxing nonequilibrated polymers in thin films at temperatures slightly above the glass transition

Chowdhury

Akhrass

Ziebert

et al. 2017

J Polym Sci B Polym Phys

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“…Previous reported measurements of drying or cracking stresses rely on the deflection of a cantilever beam [9][10][11][12] where a liquid film of a polymer solution or colloidal suspension is coated on a thin flexible plate. In such a geometry, the film dries from the edge toward the center of the film [13], which leads to spatially inhomogeneous states of the material.…”

Section: Pacs Numbersmentioning

confidence: 99%

“…However, deformations of the surface can be induced by the surface tension of a liquid drop [5][6][7] or the consolidation of a colloidal material [8], which could affect the final quality and the function of the printed device. Here, we report measurements of the drying induced stress and highlight the role of polydispersity of the suspension.Previous reported measurements of drying or cracking stresses rely on the deflection of a cantilever beam [9][10][11][12] where a liquid film of a polymer solution or colloidal suspension is coated on a thin flexible plate. In such a geometry, the film dries from the edge toward the center of the film [13], which leads to spatially inhomogeneous states of the material.However, besides the bending, when a stress is applied above a certain limit to a thin sheet, a wrinkling instability can be observed [14][15][16][17].…”

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confidence: 99%

Effect of the Polydispersity of a Colloidal Drop on Drying Induced Stress as Measured by the Buckling of a Floating Sheet

et al. 2016

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We study the stress developed during the drying of a colloidal drop of silica nanoparticles. In particular, we use the wrinkling instability of a thin floating sheet to measure the net stress applied by the deposit on the substrate and we focus on the effect of the particle polydispersity. In the case of a bidisperse suspension, we show that a small number of large particles substantially decreases the expected stress, which we interpret as the formation of lower hydrodynamic resistance paths in the porous material. As colloidal suspensions are usually polydisperse, we show for different average particle sizes that the stress is effectively dominated by the larger particles of the distribution and not by the average particle size. PACS numbers:Drying of colloidal droplets is ubiquitous in processes such as ink-jet printing technologies [1] or spray painting. Recently, new directions for printing techniques have been developed for soft materials to enable applications such as conformable electronics, soft robotics and wearable devices. For instance, electronic circuits can be printed on elastomers [2,3] and human skin [4]. However, deformations of the surface can be induced by the surface tension of a liquid drop [5][6][7] or the consolidation of a colloidal material [8], which could affect the final quality and the function of the printed device. Here, we report measurements of the drying induced stress and highlight the role of polydispersity of the suspension.Previous reported measurements of drying or cracking stresses rely on the deflection of a cantilever beam [9][10][11][12] where a liquid film of a polymer solution or colloidal suspension is coated on a thin flexible plate. In such a geometry, the film dries from the edge toward the center of the film [13], which leads to spatially inhomogeneous states of the material.However, besides the bending, when a stress is applied above a certain limit to a thin sheet, a wrinkling instability can be observed [14][15][16][17]. Recent studies focused on an elastomeric disk floating on a liquid bath with a liquid drop in the center of the disk [1,18,[20][21][22]. In these situations, the stress applied to the membrane is due to the surface tension of the involved liquids. Therefore, these studies of a deformable sheet established models based on Föppl-von Kàrmàn equations to predict the length and the number of wrinkles.In this Letter, we focus on visualizing and measuring the stress induced by the drying of a colloidal drop on a floating membrane (Fig. 1). The mechanical properties of the membrane are chosen carefully to satisfy two conditions. First, the surface tension of the pure liquid drop alone and its weight do not trigger the wrinkling instability ( Fig. 1(a)). Second, the drying-induced consolidation of the colloidal droplet, which induces a larger tensile stress in the membrane, triggers the instability ( Fig. 1(b)). From the length of the wrinkles, we can deduce the tension in the film. Our aim is to examine the effect of particle size and polydispersity ...

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“…Several points are noteworthy. (i) Although residual stress should be present in our films [5,26], it did not influence the measured surface capillary dynamics [27]. (ii) The PSD of the films after the jump from the glass-to-rubbery transition or A 2 q,short-time has two parts.…”

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confidence: 99%

Thermal-induced slippage of soft solid films

Chen

Lam

et al. 2019

Phys. Rev. E

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The dynamics of interfacial slippage of entangled polystyrene (PS) films on an adsorbed layer of polydimethylsiloxane (PDMS) on silicon was studied from the surface capillary dynamics of the films. By using PS with different molecular weights, we observed slippage of the films in the viscoelastic liquid and rubbery solid state respectively. Remarkably, all our data can be explained by the linear equation, J =-M∇P and a single friction coefficient, ξ, where J is the unit-width current, M is mobility and P is Laplace pressure. For viscous films, M is accountable by using conventional formulism. For rubbery films, M takes on different expressions depending on whether the displacements associated with the slip velocity, v s (~∇P/ξ), dominate or elastic deformations induced by ∇P dominate. For viscoelastic liquid films, M is the sum of the mobility of the films in the viscous and rubbery states.

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Direct stress measurements in thin polymer films

Cited by 29 publications

References 37 publications

Relaxing nonequilibrated polymers in thin films at temperatures slightly above the glass transition

Relaxing nonequilibrated polymers in thin films at temperatures slightly above the glass transition

Effect of the Polydispersity of a Colloidal Drop on Drying Induced Stress as Measured by the Buckling of a Floating Sheet

Thermal-induced slippage of soft solid films

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