Influence of outer-layer finite-size effects on the dewetting dynamics of a thin polymer film embedded in an immiscible matrix

Abstract

In capillary-driven fluid dynamics, simple departures from equilibrium offer the chance to quantitatively model the resulting relaxations. These dynamics in turn provide insight on both practical and fundamental aspects of thin-film hydrodynamics. In this work, we describe a model trilayer dewetting experiment elucidating the effect of solid, no-slip confining boundaries on the bursting of a liquid film in a viscous environment. This experiment was inspired by an industrial polymer processing technique, multilayer coextrusion, in which thousands of alternating layers are stacked atop one another. When pushed to the nanoscale limit, the individual layers are found to break up on time scales shorter than the processing time. To gain insight on this dynamic problem, we here directly observe the growth rate of holes in the middle layer of the trilayer films described above, wherein the distance between the inner film and solid boundary can be orders of magnitude larger than its thickness. Under otherwise identical experimental conditions, thinner films break up faster than thicker ones. This observation is found to agree with a scaling model that balances capillary driving power and viscous dissipation with a no-slip boundary condition at the solid substrate/viscous environment boundary. In particular, even for the thinnest middle-layers, no finite-size effect related to the middle film is needed to explain the data. The dynamics of hole growth is captured by a single master curve over four orders of magnitude in the dimensionless hole radius and time, and is found to agree well with predictions including analytical expressions for the dissipation.

Air sheet contraction

“…This capillary-viscous scaling is similar to what was observed by Eggers et al (1999) and Reyssat & Quéré (2006) for the contraction of an air film in a viscous liquid, or by Reyssat & Quéré (2006) and Chebil et al (2018) for the contraction of a liquid film in a viscous environment. A similar trend to our figure 3(a) was also observed in Song & Tryggvason (1999) for the contraction of a liquid film.…”

“…The rupture velocity of the air films produced in the Mesler regime follows this capillary-inertial velocity scaling for lower viscosity liquids (Thoroddsen et al 2012;Beilharz et al 2015). For higher viscosity fluids, a viscous-capillary scaling U µ would be expected (Eggers, Lister & Stone 1999;Thoroddsen et al 2005;Reyssat & Quéré 2006;Chebil et al 2018). However, much higher contraction velocities have been observed experimentally (Thoroddsen et al 2012;Langley & Thoroddsen 2019), suggesting that three-dimensional effects significantly affect the contraction dynamics in the viscous regime.…”

“…Reyssat & Quéré (2006) found that the contraction of a fluid film in a viscous liquid is limited by the friction from the surrounding liquid, leading to the velocity scaling as the capillary-viscous velocity U µ = σ /µ l with a logarithmic correction decreasing the velocity during the contraction. Chebil et al (2018) then investigated the finite-size effects on the retraction dynamics of a thin polymer film embedded in another viscous liquid between solid surfaces.…”

Capillary levelling of immiscible bilayer films

“…The stability and dewetting of thin multilayer polymer films is also a subject of interest for physicists (Lambooy et al 1996;Segalman & Green 1999;Lal et al 2017;Peschka et al 2018), and finds applications in industry e.g. materials manufactured from coextrusion processes (Zhao & Macosko 2002;Ponting, Hiltner & Baer 2010;Bironeau et al 2017;Chebil et al 2018).…”

Capillary Levelling of Immiscible Bilayer Films

“…The stability and dewetting of thin multilayer polymer films is also a subject of interest for physicists [20][21][22][23], and finds applications in industry e.g. materials manufactured from coextrusion processes [24][25][26][27].…”