Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session P4: Physics of Polymer Surfaces and Interfaces IIFocus
|
Hide Abstracts |
Sponsoring Units: DPOLY GSOFT Chair: Rob Hickey, Penn State University Room: 263 |
Wednesday, March 15, 2017 2:30PM - 2:42PM |
P4.00001: Adhesion of Photoactive Microalgae to Surfaces is Switchable by Light Oliver B\"aumchen, Christian Kreis, Marine Le Blay, Christine Linne, Marcin Makowski The natural habitats of many microorganisms are confined geometries, such as the interstitial space of rocks and soil, where interactions with interfaces and surfaces are of paramount importance. We performed \textit{in vivo} force spectroscopy experiments on the unicellular biflagellated microalga \textit{Chlamydomonas}, a prime model organism in cell- and microbiology, and discovered that the flagella-mediated adhesion to surfaces can be switched on and off by light [1]. Time-resolved micropipette experiments show that the light-switchable adhesiveness of the flagella is a completely reversible process that is based on a redistribution of adhesion-promoting flagella-membrane proteins within seconds. Light-switchable adhesion enables the cell to regulate the transition between planktonic and surface-associated state, which possibly represents a significant biological advantage for photoactive microorganisms. In terms of the colonization of surfaces and the formation of biofilms, the findings might have immediate economic and environmental relevance in biotechnological settings, such as photo-bioreactors for the sustainable production of biofuels. [1] C. Kreis, M. Le Blay, C. Linne, M. Makowski, and O. B\"aumchen, in review (2016). [Preview Abstract] |
Wednesday, March 15, 2017 2:42PM - 2:54PM |
P4.00002: Molecular mechanism for adhesion in humid conditions - lessons from spider glue Gaurav Amarpuri, Saranshu Singla, Nishad Dhopatkar, Todd Blackledge, Ali Dhinojwal Adhesion in humid conditions is a fundamental challenge for both natural and synthetic adhesives. Water lubricates the interface between the adhesive and the substrate resulting in an interfacial failure at high humidity. Yet, glue from most spider species fail cohesively at high humidity, and the spider species from wet habitat show an increase in adhesion with humidity. We use tensile testing, microscopy and surface sensitive spectroscopy techniques to probe the mechanism of spider glue adhesion under high humidity. Humidity responsive structural changes in the glue structure are observed both at the interface and in bulk. However, the humidity responsiveness is lost after washing the water soluble low molecular weight molecules (LMM) from the glue. Many natural systems display a functional response to their environment, but spider glue's humidity responsiveness is a novel adaptation that makes the glue stickiest in each species' preferred habitat. This tuning is achieved by a combination of proteins and hygroscopic LMM that respond to humidity in a unique way. We therefore anticipate that manipulation of polymer-LMM interaction can provide a simple mechanism to design humidity responsive smart adhesives. [Preview Abstract] |
Wednesday, March 15, 2017 2:54PM - 3:06PM |
P4.00003: Facile assembly of oil-water drop structures on tunable surface energy FOSM-DMA-FOSM (FDF) physical network hydrogel films Namrata Salunke, R. A Weiss, Alamgir Karim We report the confinement effects of an amphiphilic block copolymer - FDF (F: 2-(N-ethylperfluorooctane sulfonamido) ethyl methyl acrylate D: dimethyl acrylamide). A thickness dependent (40-400 nm) surface wettability gradient ranging from hydrophobic (120$^{\circ}$ ) to hydrophilic (9$^{\circ}$ ) is observed as a consequence of variation in scale of phase separation at the film-air interface. The research further reports the role played by these physico-chemically structured substrates on the unique liquidus shape of compounded droplets of oil-water mixtures. Thus examining the fundamental correlations of substrate's heterogeneous ``patchy'' properties, where two phases of contrasting surface energies are present with accompanying domain topography, to oil-water compound droplet wetting and shape molding feature aspects. We find that the unique geometries observed can be related to an effect of average substrate surface energy as observed in the case of homogeneous topographically patterned or unpatterned substrates. [Preview Abstract] |
Wednesday, March 15, 2017 3:06PM - 3:18PM |
P4.00004: Snakes and labyrinths: contact fingering instability of a soft elastic film between two rigid surfaces. Ben Davis-Purcell, Kari Dalnoki-Veress Intricate patterns are abundant in nature, from the stripes of a zebra, to the formation of snowflakes, to the wavy peaks and valleys on a beach. One such instability occurs when a soft elastomeric film bonded to a rigid substrate deforms to adhere to another rigid surface brought into contact with the film. If there is a gap between the film and the surface, then a contact fingering instability results as the film deforms to adhere to the surface. The reduction in the interfacial surface energy upon adhering is balanced by the elastic strain as the soft film deforms to span the gap and leads to distinct labyrinth patterns. We study the formation of this adhesion-induced instability and observe the fingering labyrinth pattern both statically, to measure wavelength as a function of film thickness, as well as dynamically where we see patterns similar to snakes meandering along the ground. We also investigate this contact fingering instability in the presence of an anisotropic tension in the soft elastic film. [Preview Abstract] |
Wednesday, March 15, 2017 3:18PM - 3:30PM |
P4.00005: How do rigid plates attach to a fluid-fluid interface? Liam O'Brien, Deepak Kumar, Narayanan Menon We study experimentally the dynamics of a rigid plate settling towards a fluid-fluid interface. We sediment rigid plates at low Re in silicone oil, toward an interface with a water subphase. For plates that are wet by the subphase, sedimentation is followed by a two-step attachment to the interface. The plate first slides along the interface until it becomes nearly parallel to it. Thereafter, instead of squeezing out the remaining fluid, a wetting foot from the subphase spreads over the plate. We report the time-dependence of both these stages of attachment, as well as the scaling with the dimensions of the plate. We also show experiments in which the plate is not wetted by the subphase, and a lubrication layer has to be expelled before attachment can occur. [Preview Abstract] |
Wednesday, March 15, 2017 3:30PM - 3:42PM |
P4.00006: Interfacial Properties of Thin Films of Poly(vinyl ether)s with Architectural Design in Water Yukari Oda, Nozomi Itagaki, Sin Sugimoto, Daisuke Kawaguchi, Hisao Matsuno, Keiji Tanaka Precise design of primary structure and architecture of polymers leads to the well-defined structure, unique physical properties, and excellent functions not only in the bulk but also at the interfaces. We here constructed functional polymer interfaces in water based on the architectural design of poly(vinyl ether)s with oxyethylene side-chains (POEVE). A branched polymer with POEVE parts was preferentially segregated at the air interface in the matrix of poly(methyl methacrylate). As an alternative way to prepare the POEVE surface, the cross-linked hydrogel thin films were prepared. The moduli of the hydrogel films near the water interfaces, which were examined by force-distance curve measurements using atomic force microscopy, were greatly sensitive to the cross-linking density of the polymers. Diffuse interfaces of POEVE chains at the water interface make it possible to prevent the platelet adhesion on the films. [Preview Abstract] |
Wednesday, March 15, 2017 3:42PM - 4:18PM |
P4.00007: Bulk & Interfacial Contributions to the Adhesion of Acrylic Emulsion-Based Pressure Sensitive Adhesives Invited Speaker: Qifeng Wang The performance of pressure sensitive adhesives (PSAs) depends strongly on the viscoelastic properties of the adhesive material itself and the surface that it is placed into contact with. In this work we use a multiple- oscillatory test with microindentation apparatus that is able to quantify the mechanical response of adhesive materials in the linear regime, and also in the highly strained regime where the adhesive layer has cavitated to form mechanically isolated brils. The experiments involved the use of hemispherical indenters made of glass or polyethylene, brought into contact with a thin adhesive layer and then retracted, with comprehensive displacement history. A set of model acrylic emulsion-based PSAs were used in the experiments which show a suprising degree of elastic character at high strain. The experiment result suggest that an adhesive failure criterion based on the stored elastic energy is appropriate for these systems. The primary effect of the substrate is to modify the maximum strain where adhesive detachment from the indenter occurs. [Preview Abstract] |
Wednesday, March 15, 2017 4:18PM - 4:30PM |
P4.00008: Dynamics of bound water molecules in fullerenol at different hydration levels Yilin Wang, Steven Robey, Janice Reutt-Robey Fullerenols, polyhydroxylated fullerenes, are of great interest as promising materials in medical application because of their high water solubility and biocompatibility. Fullerenols are highly responsive to their environment, for example, they readily undergo hydration under ambient conditions. Understanding the dynamics of water molecules bound to fullerenols, and the interplay between water molecules and fullerenols is important in realizing biological function. Here, broadband dielectric spectroscopy (BDS), was performed on a fullerenol with 44 hydroxyl groups, C60(OH)44, between 300 K and 340 K. At room temperature and under ambient conditions, C60(OH)44 is hydrated, releasing bound water molecules with increasing temperature, as quantified by thermal gravimetric analysis (TGA) measurements. At room temperature, a dielectric band due to collective bulk-like dynamics of the bound water molecules is observed. The relaxation peak of the water molecules shifts to higher frequency with increasing of temperature, reflecting the dynamics of bound water. Upon loss of water molecules, either thermally induced or vacuum induced, the relaxation peak shifts to lower frequency. The stoichiometric relationship between the dielectric properties of the hydrated fullerenol and the interplay between the bound water molecules and C60(OH)44 will be discussed. [Preview Abstract] |
Wednesday, March 15, 2017 4:30PM - 4:42PM |
P4.00009: block copolymer stabilized emulsion drops Damith Rozairo, Andrew B. Croll Emulsion droplets play an important role in countless industrial systems, polymer synthesis and even advanced schemes for drug delivery. Many researchers have adopted block copolymer surfactants for the added functionality that polymer chemists can create. Currently, much understanding of block copolymer coated emulsion droplets has been inferred from the behaviour of small molecule surfactants, however, this may be misleading. In this work we study the approach of a polystyrene-poly (ethylene oxide) coated oil drop to a smooth flat surface using confocal microscopy. We find a slow drainage dynamic that is unique to the long block copolymer molecules. We use a simple scaling model to highlight the importance of three length scales in the problem: the hydrodynamic slip length, the brush height, and the width of a ‘rim’ formed as the drop buckles during approach to the flat surface. Understanding this approach process is critical to understanding surface wetting, coalescence and other basic emulsion phenomena. [Preview Abstract] |
Wednesday, March 15, 2017 4:42PM - 4:54PM |
P4.00010: Abstract Withdrawn
|
Wednesday, March 15, 2017 4:54PM - 5:06PM |
P4.00011: Elastic properties, reaction kinetics, and structural relaxation of an epoxy resin polymer during cure Manon Heili, Andrew Bielawski, John Kieffer The cure kinetics of a DGEBA/DETA epoxy is investigated using concurrent Raman and Brillouin light scattering. Raman scattering allows us to monitor the \textit{in-situ} reaction and quantitatively assess the degree of cure. Brillouin scattering yields the elastic properties of the system, providing a measure of network connectivity. We show that the adiabatic modulus evolves non-uniquely as a function of cure degree, depending on the cure temperature and the molar ratio of the epoxy. Two mechanisms contribute to the increase in the elastic modulus of the material during curing. First, there is the formation of covalent bonds in the network during the curing process. Second, following bond formation, the epoxy undergoes structural relaxation toward an optimally packed network configuration, enhancing non-bonded interactions. We investigate to what extent the non-bonded interaction contribution to structural rigidity in cross-linked polymers is reversible, and to what extent it corresponds to the difference between adiabatic and isothermal moduli obtained from static tensile, i.e. the so-called relaxational modulus. To this end, we simultaneously measure the adiabatic and isothermal elastic moduli as a function of applied strain and deformation rate. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700