Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session X08: Surfaces, Interfaces, Thin Films, and CoatingsLive
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Sponsoring Units: DPOLY Chair: Hee Jeung Oh, Pennsylvania State University |
Friday, March 19, 2021 8:00AM - 8:12AM Live |
X08.00001: Geometry-Dictated Wrinkle Patterns in Vapor-Deposited Thin Films Robert Enright, Laura Bradley Surface patterns and wrinkles in thin films are of fundamental and technological interest for their utility in tuning morphological, mechanical, and surface properties. Here, we present a method to produce fluoropolymer films which spontaneously wrinkle when deposited onto soft substrates via the solvent-free initiated chemical vapor deposition (iCVD) process. The iCVD technique is a surface polymerization process that affords a wide monomer library and the ability to deposit polymers onto substrates of arbitrary shape. We demonstrate control over wrinkle pattern selection on silicone oil substrates as a function of surface topography, boundary shape, and deposition conditions. Here, we present relationships between substrate shape and wrinkle pattern selection, and we examine the underlying mechanism of wrinkling during film growth. |
Friday, March 19, 2021 8:12AM - 8:24AM Live |
X08.00002: Polymer Colloidal Crystals reinforced by Supercritical Fluids Visnja Babacic, Jeena Varghese, Emerson Coy, Eunsoo Kang, Mikolaj Pochylski, Jacek Gapinski, George Fytas, Bartlomiej Graczykowski Colloidal crystals realized by self-assembled polymer nanoparticles are highly attractive for visible light photonics, GHz phononics and superhydrophobic coatings. However, their fragility remains one of the main concerns when it comes to applications. Here, uniform mechanical reinforcement and tunability of 3D polystyrene colloidal crystals, by means of supercritical nitrogen and argon, is presented. This method is a synergistic combination of nanoscale plasticization of particles surface and compressive hydrostatic pressure that leads to strengthening at temperatures well below the glass transition. It results in the formation of permanent physical bonds between the particles while maintaining their shape and periodic arrangement, which we term "soldering". We employed Brillouin light scattering to monitor in-situ the mechanical vibrations of the crystal and thereby determine preferential pressure, temperature and time ranges for soldering. This method offers a chemical-free and efficient solution for fabrication and tuning of durable devices. Moreover, plasticization of polymeric nanostructures by means of supercritical fluids offers new effects and opportunities. |
Friday, March 19, 2021 8:24AM - 8:36AM Live |
X08.00003: Fabrication of uniform thick films through dip-coating with vibration Jeongrak Lee, Hyunsu Kwak, Byungho Lee, Anna Lee We study the fabrication of uniform thick polymeric films based on the dip-coating with vibration. In conventional dip coatings established by the Landau-Levich-Derjaguin theory, the fast process generates a coating thickness gradient while the slow process limits the film thickness and is time-consuming. Recently, fabrication method of thick films was proposed based on the dipping of a solid substrate in a neutral buoyancy bi-layer liquid bath and applying vibration. The film thickness is tailorable by varying the vibration frequency and amplitude. We conduct systematic experiments to analyze the physical ingredients that affect coating thickness. We find the inverse proportional relationship between the applied mechanical energy during an oscillation and the final coating thickness that is independent of an initial coating shape determined by the dipping rate. We also find that the viscosity has a little influence on the coating thickness while the density increase of the supporting liquid for neutral buoyancy formation reduces the coating thickness. Our results can be used to efficiently fabricate Functionally Graded Material. |
Friday, March 19, 2021 8:36AM - 8:48AM Live |
X08.00004: Random, Amphiphilic, Charged Copolymers for Protein Encapsulation in Solution and at Interfaces Curt Waltmann, Jeremy Wang, Monica Olvera De La Cruz Random copolymers with hydrophobic, hydrophilic, and charged groups are investigated using simulation and experiments for their ability to encapsulate a proteins in aqueous solution and at interfaces. Experiments are performed on a protein known as PETase, which depolymerizes polyethylene terephthalate (PET). In aqueous solution, we show the formation of complexes slightly larger than the protein itself. In the presence of PET film substrate, an increase in activity is observed in response to thermal challenge. MARTINI simulations show the formation of protein-polymer complexes and are used to optimize these complexes by changing the relative amounts of the 3 different types of monomers. These simulations also show the formation of complexes at elevated temperature and that the polymer can stabilize the conformation of the protein at high temperature. Simulations using cytochrome P450 show that the ability of our random copolymers to form complexes is general. Finally, we show the behavior of these protein-polymer complexes in the presence of interfaces (PETase in the presence of a PET film, P450 in the presence of an oil water interface). |
Friday, March 19, 2021 8:48AM - 9:00AM Live |
X08.00005: Diffusion Kinetics and Capacitive Dye Removal by Block Copolymer Based Porous Carbon Fibers Joel Serrano, Assad Ullah Khan, Tianyu Liu, Alan Roger Esker, Guoliang Liu Block copolymer based porous carbon fibers (PCFs) have hierarchical pores, high surface areas, and excellent electrical/ion conductivities. The PCF contains hierarchical macro-, meso-, and micropores with a surface area of 780 m2 g−1 . The electrosorptive behavior of PCF is well described by the Langmuir isotherm and the Weber–Morris model. Based on the model, the interconnected hierarchical pores contribute to easy accessibility of dye ions to the inner surface sites within PCF, resulting in a high electrosorption capacity of 1360 mg g−1 , reaching ≈87% of the theoretical maximum. Thanks to the hierarchical pores that allow for rapid ion desorption, the PCF can easily be regenerated. Lastly, depending on the electrode configuration, the PCF can selectively remove anionic dye, cationic dye, or both. The findings herein provide a fundamental understanding of electrosorptive behavior of block copolymer based porous carbon fibers, enabling future development in filtration materail. |
Friday, March 19, 2021 9:00AM - 9:12AM Live |
X08.00006: Topological waves in passive and active fluids on curved surfaces Richard Green, Jacome Armas, Jan de Boer, Luca Giomi Topological methods are well-established in hard condensed matter, and recently similar approaches have been shown to explain phenomena in soft condensed matter. In this talk I will examine two soft matter systems, one passive and one active, and consider how the models and topological modes are connected. I solve for these modes directly without recourse to the bulk-edge correspondence and provide an index theorem linking the number of modes determined by the topology of momentum-space to the real-space topology of the surface on which they are hosted. Our work suggests some simple rules to engineer topological modes on surfaces in passive and active soft matter systems. |
Friday, March 19, 2021 9:12AM - 9:24AM Live |
X08.00007: Non-Hermitian delocalization of interacting directed polymers on periodic substrates Alexander Patapoff, Abhijeet Melkani, Jayson Paulose Non-Hermitian Hamiltonians describe the dynamics of systems experiencing energy flow, gain, and loss in a variety of physical settings. When combined with periodic potentials, non-Hermiticity brings new twists to band-based phenomena such as topological modes and metal-insulator transitions. We explore the interplay of band theory and non-Hermitian mechanics in a classical system of interacting directed polymers on a substrate with periodic grooves. At thermal equilibrium, the density profiles of the polymers map onto the quantum statistics of fermions experiencing a constant imaginary vector potential in addition to the (real) periodic substrate potential. The strength of the vector potential, which renders the problem non-Hermitian, is controlled by a transverse shear force applied to the polymer ends. By ramping up the shear, we drive a transition from a localized band-insulator state with each polymer aligned to a unique groove, to a tilted configuration in which polymers are delocalized across many grooves. Besides advancing known mechanisms of delocalization in directed polymers, our results provide a purely classical manifestation of non-Hermitian band physics enabled by thermal fluctuations and interactions. |
Friday, March 19, 2021 9:24AM - 9:36AM Live |
X08.00008: Structural changes during drying of nano-aggregated inks jianqi wang, Kabir Rishi, Greg Beaucage, Ivan Kuzmenko With increasing concentration above the overlap concentration, nanoaggregates become entwined and structural information at scales larger than an emergent mesh size are obscured. When observed in small-angle scattering, this is termed structural screening and is observed in the low-q regime. While observed as a function of concentration in solutions, structural screening is also apparent on relatively thick dried nano-aggregate layers such as in a dried ink plaque or a paint chip. In addition to this screening effect, emergent micron-scale network structures are often observed. These micron-scale structures may be responsible for optical properties in pigments and mechanical properties in reinforced elastomers. In investigating thin printed layers of nanoparticles, it was found that the impact of structural screening on the measurement of aggregate structures can be minimized in thin samples such as inkjet-printed layers of nano-aggregates with thicknesses on the order of less than 100 times the nano-aggregate size. |
Friday, March 19, 2021 9:36AM - 9:48AM Live |
X08.00009: Self-assembly of Block Copolymers in Thin Films with Photo-Induced Solid-State Conversion Mingqiu Hu, Xindi Li, Javid Rzayev, Thomas Russell Keeping up with Moore’s law becomes increasingly difficult as top-down photolithography approaches the diffraction limit. Bottom-up self-assembly of block copolymers (BCPs) in thin films serves as a promising solution to achieve patterns with sub-10 nm feature size, high lateral ordering, and good etching contrast. We developed a series of high-X low-N block copolymers using solid-state conversion from phase-mixed poly(solketal methacrylate)-b-polystyrene to strongly microphase-separated poly(glycerol monomethacrylate)-b-polystyrene, where X was massively increased. Before conversion, the BCPs are soluble in toluene, enabling spin-coating of thin films with uniform thickness. The solid-state conversion was achieved with either trifluoroacetic acid vapor or exposing polymer films embedded with photoacid generators to UV light followed by post-exposure baking. Lamellae oriented perpendicular to the substrate was achieved by neutralizing the interfacial interactions between the two blocks by modifying the substrate with poly(solketal methacrylate)-random-polystyrene which undergoes solid-state conversion simultaneously with the BCPs. |
Friday, March 19, 2021 9:48AM - 10:00AM Live |
X08.00010: On the stability of initiators for surface-initiated controlled radical polymerization Christian Pester The covalent attachment of polymers has emerged as a powerful strategy for the preparation of multi-functional surfaces. Patterned, surface-grafted polymer brushes provide spatial control over a variety of physical properties and allow for fabrication of ‘intelligent’ substrates which selectively adapt to their environment. However, the route towards such patterned polymer brush surfaces often remains challenging, creating a demand for more efficient and less complicated fabrication strategies. Here, we describe recent advances in our group in reduction photolithography to produce topographically and chemically pattern polymer brushes by using light-mediated controlled radical polymerization. We highlight recent work on expanding our technique towards photoinduced electron/energy transfer (PET) reversible addition–fragmentation chain transfer (RAFT) polymerization. We present findings regarding the long-term stability of the surface-grafted initiating sites and discuss reproducibility of SI-PET-RAFT and other polymerization techniques. |
Friday, March 19, 2021 10:00AM - 10:12AM Live |
X08.00011: Antimicrobial Surface Modification via Self-Assembled Nanopatterns of Block Copolymer Films Daniel Salatto, Todd Benziger, Yashasvi Bajaj, Zhixing Huang, Benjamin M Yavitt, Mikihito Takenaka, David Thanassi, Maya Endoh, Tad Koga Fouling is the undesirable accumulation of a material on a variety of objects and has become a global problem. Surface topology is of great interest to develop bactericidal surfaces in place of traditional chemical-based approaches that are often toxic to humans and the environment. In this talk, we use nanopatterned surfaces fabricated by polystyrene-block-poly(methyl methacrylate) diblock copolymers as rational models. Oriented, self-assembled PS cylinders or lamellae were cross-linked by UV and the PMMA was removed by acetic acid. Our results with PS nanopillars (25 nm height & 60 nm spacing) showed bactericidal properties against Escherichia coli (E coli), while bacteria remain rod-shaped on “flat” PS or PMMA control surfaces. It was also found that PS nanowalls with height and spacing of about 20 nm show a similar bactericidal property, while the efficiency was much less when compared to the PS nanopillars. We will discuss the roles of geometric parameters of nanopatterned surfaces in bactericidal properties against the model bacterium. |
Friday, March 19, 2021 10:12AM - 10:24AM Live |
X08.00012: Solvated Polymer Translocation Under Confinement Using an Entropic Barrier Model Neha Manohar, Robert Riggleman, Kathleen Joan Stebe, Daeyeon Lee In this study, we probe the effect of polymer-surface interactions on the kinetics of confined polymer translocation through an entropic barrier between two cavities and investigate how this effect varies with solvent quality (excluded volume interactions) and confinement. The free energy landscape within the cavities is obtained by self-consistent field theory (SCFT) calculations, and these free energies are used to determine the mean translocation time of polymer from one cavity to another. It is found that the mean translocation time is strongly dependent on the strength of the polymer-surface interactions and shows a non-monotonic dependence with interaction strength. Two competing factors contribute to the non-monotonicity: the excluded volume effect and the polymer-surface interaction strength. Kinetics initially get faster with increasing polymer-surface interactions, but eventually slow down as interactions become strong enough for adsorption to occur. As excluded volume increases, this transition into slower kinetics shifts toward stronger interactions. Furthermore, when translocation occurs between cavities of different sizes, the behavior is monotonic, with smaller cavities becoming more favorable at higher interaction strengths. |
Friday, March 19, 2021 10:24AM - 10:36AM On Demand |
X08.00013: Interactions between Colloidal Particles Mediated by Nonadsorbing Polymers: Casimir and Anti-Casimir Effects Pengfei Zhang, Qiang Wang Using a lattice self-consistent field (SCF) theory and the corresponding lattice Monte Carlo (MC) simulations combined with our recently proposed Z method [Soft Matter 11, 862 (2015)], we examined homopolymer solutions confined between two parallel and nonabsorbing surfaces and in equilibrium with a bulk solution, and accurately calculated the effective interaction between the two surfaces. Close to the critical point of the bulk solution, we found for the first time the Casimir effect with long-range attractive intersurface potential W<0 extending to D/Re≈10, where D denotes the intersurface separation and Re the root-mean-square chain end-to-end distance in the bulk solution. On the other hand, by directly comparing our MC results with SCF predictions based on the same model system, we were able to quantitatively and unambiguously distinguish the mean-field and the fluctuation contributions to W, and found for the first time the fluctuation-induced repulsion W>0 between the two surfaces at intermediate D≈Re (i.e., the anti-Casimir effect) predicted by Semenov and Obukhov [S. P. Obukhov and A. N. Semenov, Phys. Rev. Lett. 95, 038305 (2005)], which is about one order of magnitude stronger than that due solely to the finite chain length given by the SCF theory. |
Friday, March 19, 2021 10:36AM - 10:48AM On Demand |
X08.00014: Patterning Polyacrylonitrile Thin Films Using Capillary Force Lithography Chuqing Yuan, Rebecca Barry, Tanguy Terlier, Kathryn Beers, Alamgir Karim Polyacrylonitrile (PAN)-based conductive graphitic microstructures have tremendous potential for a variety of applications such as patterned electrodes, and anisotropic conductive films in the electronics industry because of its high carbonization yield. However, due to the crystallinity and high melting point of pristine PAN, thin films are difficult to get patterned at routine oven temperatures via methods such as capillary force lithography (CFL), a facile and low-cost lithographic technique. Herein, we demonstrate that simply adding a small amount of an ionic liquid (IL) can greatly improve the imprintability of PAN by decelerating the crystallization rate and providing PAN with the required mobility at accessible temperatures for efficient mold filling. The effect of IL additive concentration, annealing temperature and hold time on patterned PDMS mask on imprintability of PAN are well-correlated in a balancing act. The resulting patterned films demonstrate extraordinary IL removal ability at the end of the process, outstanding thermal stability of final patterned structures, and promising results on easy patterning route to fabricate graphitic microstructures after carbonization for a multitude of applications ranging from sensors to membranes. |
Friday, March 19, 2021 10:48AM - 11:00AM On Demand |
X08.00015: Polycaprolactone for Inorganic Materials Infiltration: A Promising Addition to Sequential Infiltration Synthesis Polymer Family Mahua Biswas, Joseph A Libera, Seth B Darling, Jeffrey W Elam Infiltration of inorganic materials inside polymers is receiving a lot of attention for creating hybrid materials and patterned nanostructures. Sequential infiltration synthesis (SIS), derived from atomic layer deposition (ALD), involves gas phase reactions to infiltrate polymers with inorganic materials. The reactions between various polymer functional groups and inorganic precursors are unique, which makes it essential to understand the specific interactions for a range of precursors and polymers to enable predictive process design for applications. In this work, in situ Fourier transform infrared spectroscopy (FTIR) measurements have been performed during Al2O3 and TiO2 SIS in three homopolymers: poly(methyl methacrylate) (PMMA), poly(ε-caprolactone) (PCL), and poly(2-vinylpyridine) (P2VP). From the FTIR intensity, it is shown quantitatively that the interaction dynamics of these polymers with the metal precursors are substantially different. A key finding from this comparative study is that PCL interacts far more strongly with metal precursors compared to PMMA and P2VP. PCL may be an attractive polymeric template for inorganic infiltration processes, which has not been reported previously. |
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