Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session W18: Physics of FoamsFocus Recordings Available
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Sponsoring Units: DPOLY Chair: Valeriy Ginzburg, Michigan State University Room: McCormick Place W-184D |
Thursday, March 17, 2022 3:00PM - 3:36PM |
W18.00001: The coarsening of very wet foams in two and three dimensions Invited Speaker: Douglas J Durian Two dimensional foams that are dry, consisting of space-filling bubbles separated by thin films of negligible thickness, are far from equilibrium and evolve with time by the diffusion of gas across the films from small low-pressure bubbles into large low-pressure bubbles. This is described by the von Neumann law, dA/dt=K(n-6) where A is the area of an n-sided bubble, the collective effect of which brings the foam to a self-similar scaling state where the average area grows as the square root of time. In this talk, I will point out the important of the area-weighted side number distribution and I will review our efforts to generalize the von Neumann law to wet foams. We find that gas transport is not just across films but also happens to a surprisingly large degree across liquid-inflated Plateau borders shared by three neighboring bubbles. This gives rise to behavior that depends on bubble size and shape, which we confirm by experiment. Translating this effect to three dimensional wet foams gives insight into a puzzling observation that foams at the jamming transition coarsen with the same power-law time dependence as a froth of dilute bubbles. In particular, we predict a logarithmic correction that was not evident in early observations. |
Thursday, March 17, 2022 3:36PM - 3:48PM |
W18.00002: Dynamic interplay between flow and bubbles in polymer foaming drives surprising consequences for nucleation and ripening Andrew S Ylitalo, Huikuan Chao, Thomas C Fitzgibbons, Valeriy Ginzburg, Weijun Zhou, Richard C Flagan, Zhen-Gang Wang, Julia Kornfield Polymer foams are often born through high supersaturations of dissolved gas and high shear stresses from the nozzle. Just as high supersaturation nucleates bubbles that reduce local viscosity and drive flow, so can high shear stresses mix dissolved gas back into depleted regions and drive bubble nucleation. This dynamic interplay between bubbles and flow has a significant impact on foam structure but lacks experimental study due to the stochasticity of homogeneous nucleation and challenge of observing such short time and length scales. |
Thursday, March 17, 2022 3:48PM - 4:00PM |
W18.00003: 3D Printing of Thermally Activated Polymer Foams with Controlled Porosity and Tunable Mechanical Properties via Digital Light Processing Younghoon Kwon, Megan T Valentine, Craig J Hawker, Soyoung E Seo, Neil D Dolinski, Jeffrey L Self, Caitlin S Sample, Christopher Bates Many natural lightweight materials display a distinctive combination of low density, high strength and high toughness. These unique features are achieved through complex hierarchical architectures that introduce porosity and have characteristic dimensions spanning from the nano- to macroscale. This level of control, however, has been proven difficult to mimic synthetically in polymeric materials, limiting the use of soft porous composites in load-bearing applications. To address this challenge, we developed a two-step process involving 3D photopolymerization followed by a thermal processing step to fabricate thermally-activated polymer foams with tunable porosity and material properties. The material is processed by incorporating stimuli-responsive microspheres that act as a foaming agent into a photocurable resin leading to microporosity throughout the resulting polymer network. During thermal treatment, 3D printed objects undergo irreversible volume expansion while maintaining their geometry. Structural analysis and mechanical characterization on the polymer foams showed that a broad range of porosities up to 75% and tunable specific moduli can be achieved. Implementing this approach allows the development of lightweight materials with superior bulk properties for applications in aerospace and biomedicine. |
Thursday, March 17, 2022 4:00PM - 4:12PM |
W18.00004: Bubble nucleation in the surfactant stabilized polyol-CO2 mixtures: Insights from a classical density function theory study Sriteja Mantha, Huikuan Chao, Andrew S Ylitalo, Benjamin Laccetti, Thomas C Fitzgibbons, Weijun Zhou, Valeriy Ginzburg, Richard C Flagan, Julia Kornfield, Zhen-Gang Wang Silicone-polyether (SPE) surfactants, made of poly dimethyl-siloxane backbone and polyether branches, are commonly used to stabilize the polyol-CO2 foam formulation. The SPE surfactants reduce interfacial tension between polyol-CO2 interface, promote bubble generation and impacts the foam cell size. However, the mechanism through which SPE surfactants affect the nucleation and stability of the bubbles is not well understood. We find that increase in the CO2 concentration in the polyol+CO2+SPE system leads to significant decrease in the SPE CMC. This underscores the importance of CO2 bubble nucleation from a pre-formed micelle. In this work using classical density functional theory we will compare and contrast our observations on the CO2 bubble nucleation from a homogeneous polyol+CO2+SPE mixture and from a preformed SPE micelle in the system. |
Thursday, March 17, 2022 4:12PM - 4:24PM |
W18.00005: Fabrication of hybrid inorganic-organic foams by atomic layer deposition and sequential infiltration synthesis Kirti Sankhala, Tamar Segal-Peretz Open-cell polymer foams are widely used in various applications, such as supporting material, heat insulator, chemical or oil absorbent, acoustic or energy damper etc. However, the mechanical strength, abrasion resistance, prone to flaming and degradation remain a challenge in these foams due to the softness associated with the polymers. Herein, we modify the conventional polymeric foams to hybrid polymer-ceramic foams using atomic layer deposition (ALD) and sequential infiltration synthesis (SIS) for metal oxide growth (e.g., ZnO, Al2O3 and TiO2) onto and within the polymer strands of the foam, respectively. ALD offers sub-nm precision in coating thickness while SIS offers unique process for growth of nanoclusters within the polymer. This highly versatile system enables application-based design of nano- to macro-scale structures and hybrid composition in foams. Detailed analysis of ceramic growth on and within the foams and correlation between the physical, chemical, mechanical and flame-retardance properties varied by structural and composition parameters enables the optimization of the hybrid composite, achieving the desired performance. |
Thursday, March 17, 2022 4:24PM - 4:36PM |
W18.00006: A Generalized Size-Topology Identity for 2-dimensional Dry Foams Anthony T Chieco, James P Sethna, Douglas J Durian Two-dimensional dry foams coarsen according to the von Neumann law as dA/dt ∝ (n-6) where n is the number of sides of a bubble with area A. Such foams reach a self-similar scaling state where area and side-number distributions are stationary. Combining self-similarity with the von Neumann law, we derive a new identity connecting moments of the area distribution with averages of the side-number distribution that are weighted by powers of bubble area. To test this prediction, we collect and analyze high precision image data for a large number of bubbles squashed between parallel acrylic plates and allowed to coarsen into the self-similar scaling state. We find good agreement for moments ranging from two to nineteen. This enables derivation of another identity, which we are now testing, connecting the rate of change of the moments of the area distribution with area-weighted averages of the side-number distribution. |
Thursday, March 17, 2022 4:36PM - 4:48PM |
W18.00007: Foam Film Drainage and Nanoscopic Topography of Micellar Sodium Caseinate Solutions Lena Hassan, Vivek Sharma, Chenxian Xu, Michael Boehm, Stefan Baier Proteins in food, cosmetic and pharmaceutical foams influence the interfacial and bulk properties of formulations. In this study, we characterize the drainage of protein-based foams as well as single foam films, and contrast their behavior with micellar foams formed with small molecular surfactants above the critical micelle concentration. Micellar foam films undergo drainage via stratification manifested as step-wise thinning in the plots of average film thickness over time. Stratification in micellar foam films is accompanied by formation of coexisting thick-thin regions visualized in reflected light microscopy as exhibiting distinct grey regions as intensity is correlated with thin film interference. We critically examine the drainage of protein foam films to determine how and when stratification can be observed, and evaluate the connection between drainage of single foam films and bulk foams.We find that unlike flat domains in micellar SDS solutions with a sharp and circular moving front, and non-flat features we identify as nanoridges and mesas, the micellar NaCas solutions display non-flat domains, that grow by creating non-circular domains. |
Thursday, March 17, 2022 4:48PM - 5:00PM |
W18.00008: foam coarsening under steady shear : interplay between bubble rearrangements and film thinning dynamics Arnaud Saint-Jalmes, corentin tregouet Aqueous foams are unstable and age by drainage and coarsening.Today, these effects are well described, as well as their impact on foam properties. For instance, the foam viscoelasticity evolve in time due to coarsening which increases the bubble size. Here, we investigate the reverse coupling, and study if and how a continuous flow of a foam can impact its dynamics of coarsening. We introduce a new protocol where brief oscillatory measurements are inserted within a steady shear, allowing us to monitor the relative variation of the bubble size with time, and as a function of an applied shear. It turns out that the coarsening rate is strongly impacted by the applied shear: it is continuously reduced above a critical shear rate, which decreases itself with the bubble size. This coarsening reduction is interpreted as the result of out-of-equilibrium and shear-dependant film thicknesses, being higher than at rest. The critical shear rate, above which films are dynamically sustained at high thickness, emerges from the competition between the rate of rearrangements and the time to drain thick films created during a rearrangement. We thus report here a first experimental proof of out-of-equilibrium film thicknesses within a sheared foam, and of the impact this has on coarsening. |
Thursday, March 17, 2022 5:00PM - 5:12PM |
W18.00009: Instability of the 1D thickness profile at the edge of a horizontal foam film and its Plateau border Corentin Tregouet, Isabelle Cantat The stability of soap bubbles and hence of liquid foams is a set by the film thinning, which is known to occur locally: rounds patches of thin films appear at the edges of the film before moving to the top of the film by buoyancy. This phenomenon, called the marginal regeneration, has been observed for decades, but its origin hasn't yet been established. It involves the appearance of a localized pinched region between the film and the meniscus, which dynamics has been entirely characterized by assuming its invariance in the direction of the meniscus. We identify a limit in which the bulk drainage and the surface rearrangements are decoupled, the film thus evolving in a sliding-puzzle-like dynamic. In this frame, we study theoretically and numerically the stability of this straight pinched region, and show that it is unstable to long wavelengths. We predict a critical wavelength of fastest destabilization and a thickness ratio between the thin and thick parts of the film, both in good agreement with experimental observations. |
Thursday, March 17, 2022 5:12PM - 5:24PM Withdrawn |
W18.00010: The stability of saline foams Anand Yethiraj, Tatsuo Izawa, Lesley A James If one drills for oil, the extraction process should be as efficient as possible. Yet, the technology for extracting crude oil from reservoirs beneath the ground involves an inherently unstable step: that is, the pumping of the less viscous water into a more viscous medium. This results in the “viscous fingering instability” which leaves islands of unrecoverable oil behind. |
Thursday, March 17, 2022 5:24PM - 5:36PM |
W18.00011: Ultra-high thermally and electrically conductive polymer-expanded graphite composites Fatema Tarannum, Swapneel S. Danayat, Avinash Nayal, Rajmohan Muthaiah, Jivtesh Garg
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Thursday, March 17, 2022 5:36PM - 5:48PM |
W18.00012: Robust Co-continuous Nanostructures by Microphase Separation of Randomly Cross-linked Polystyrene and Poly(2-vinylpyridine) Networks Jaechul Ju, Ryan C Hayward Co-continuous polymeric nanostructures have drawn considerable attention due to their synergistic effect, for example, each constituting polymer maintains its properties without significant loss in all three dimensions due to percolation, in contrast to non-percolated morphologies where the characteristics of the dispersed morphologies may be largely lost. Randomly end-linked copolymer networks (RECNs) have been shown to facilitate the formation of co-continuous nanostructures in a robust way. However, the requirement of using telechelic polymers often necessitates complicated synthetic routes. Alternatively, randomly cross-linked copolymer networks (RCCNs) are composed of polymers with crosslinkable pendants that are easily synthesized by copolymerization, promoting more general copolymer network paths for percolating structures. RCCNs provide a high degree of tunability of polymer chain- and crosslinker functionalities, both of which have been investigated in this study. Wide co-continuous windows have been defined by a selective extraction of one polymer coupled with a variety of characterization methods (gravimetry analysis, small-angle X-ray scattering, and electron microscopic images). Potential applications of the resulting porous monolith and re-collection of the washed polymer will be further studied. This RCCN platform is expected to facilitate processing of co-continuous polymer nanostructures. |
Thursday, March 17, 2022 5:48PM - 6:00PM |
W18.00013: High Performance, Tunable Sensory Platform Based on Porous Ionogels for Electrical and Optical Dual-Output Jin Han Kwon, Yong Min Kim Here, we propose porous ion gels for high-performance, functional ionic sensory platforms. The porous ion gels can be effectively deformed by closing pores even with small pressure, and a large change in the contact area of the gel and the electrode is induced, leading to a significant difference in electrical double layer capacitance. The porous ion gels are applied to ionoskins after optimizing mechanical characteristics by adjusting gel parameters. The device indicates a high sensitivity of ∼152.8 kPa−1, a broad sensory pressure range (up to 400 kPa), and excellent durability (>6000 cycles). Successful monitoring of various human motions that induce different magnitudes of pressure is demonstrated with high precision. More interestingly, the functionality of the porous ion gel is extended to include electrochemiluminescence (ECL), resulting in the production of emissive ECL ionoskins. The ECL intensity from the emissive ionoskin is linearly correlated with the applied pressure, which can even be inferred even by the naked eye. |
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