Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session X35: Kinetics and Aggregation of Polymers in Complex Fluids and Geometries |
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Sponsoring Units: DPOLY DSOFT Chair: Jeffrey Ethier, Illinois Institute of Technology Room: 507 |
Friday, March 6, 2020 11:15AM - 11:27AM |
X35.00001: Network Centrality of Heterogeneous Elastomers for Describing Mechanical Property Yoshifumi Amamoto, Ken Kojio, Atsushi Takahara, Yuichi Masubuchi, Takaaki Ohnishi There have been a lot of attempts to describe structure-property relationships of heterogeneous elastomers. However, it is hard to evaluate the heterogeneity quantitatively. In this presentation, we report the network structure of the elastomers in terms of connectivity was evaluated based on centrality, one of indicators utilized in complex network science, and its effect for the mechanical property was investigated. A construction and a uniaxial elongation of elastomers were performed with coarse-grained molecular dynamics simulation. End-to-end distance of partial chains, which strongly affect stress in entropy elasticity was evaluated. We found that the end-to-end distance increased with increasing the network centrality. Furthermore, network centrality incorporating initial end-to-end distance could be a unified indicator for the mechanical property of the heterogeneous elastomers. We think the complex network could be one of the suitable approaches to reveal structure-property relationships of materials. |
Friday, March 6, 2020 11:27AM - 11:39AM |
X35.00002: Understanding aggregation and growth in a cross-linked polymer film Tine Curk, Erik Luijten Oil paints, used by celebrated artists such as Rembrandt, Picasso, Dalí and others, are composite materials consisting of pigment nanoparticles and polymerized drying oil. Dissocation of the pigment results in metal ions that react with the oil, yielding an insoluble metal soap. Over time scales of decades to centuries, these metal soaps aggregate, forming visible clusters and thus tainting the original work of art. |
Friday, March 6, 2020 11:39AM - 11:51AM |
X35.00003: Influence of particle softness on the flow properties of colloidal dispersions: A comparison of regularly and ultra-low-crosslinked microgels Carlos Lopez, Andrea Scotti, Monia Brugnoni, Steffen Bochenek, Jerome Crassous, Walter Richtering Soft, adaptive microgels are potential building blocks for smart materials with precisely controlled viscoelastic properties that are highly responsive to environmental conditions. We compare the flow properties of different PNIPAM microgels: regularly crosslinked and ultra-low crosslinked (ULC) microgels. We show that the flow properties of ULC microgels reveal a colloid-to-polymer transition with increasing solution concentration. At low concentrations, the viscoelastic properties and phase behaviour of ULC microgels are identical to those of regularly crosslinked microgels. With increasing concentration, the viscosity and plateau modulus display a much weaker increase for ULC relative to regularly cross-linked systems. Oscillatory rheology in the linear viscoelastic region reveals that for regularly crosslinked microgels in concentrated solution, the flow properties are determined by the highly cross-linked core, while for ULC microgels the brush-like interaction is dominant. |
Friday, March 6, 2020 11:51AM - 12:03PM |
X35.00004: Electrostatics and Rheology of Unentangled Semidilute Polyelectrolyte Solutions Guang Chen, Antonio Perazzo, Howard A Stone Polyelectrolytes (PE) are charged polymers in polar solvents. Classical scaling theory suggests that the viscosity η for salt-free semidilute unentangled PE solutions in Θ solvents obeys the empirical Fuoss law η∼c1/2 in the higher polymer concentration (c) regime, and η∼c5/4 in the lower c regime. However, recent experiments have also reported η∼c0.68 and η∼c0.91, which are at odds with the classical scaling theory. To rationalize the four distinct scaling laws, we probe the electrostatic energy per monomer under the influence of salt and their contributions to the viscosity of PE solutions. We identify four consecutive regimes dependent on the magnitude of the ratio of the polymer concentration over the salt concentration, which capture the unexplained observations and classical PE solution theories, and provide physical insights for the effects of salt contamination and added salt on the properties of both weakly and strongly charged semidilute unentangled PE solutions. |
Friday, March 6, 2020 12:03PM - 12:15PM |
X35.00005: Patterned fluorescence photobleaching recovery on multicomponent sodium polystyrene sulfonate solutions to investigate temporal aggregrate formation. Paul Balding, Paul Russo, Rachel Borrelli Patterned fluorescence photobleaching recovery was used to investigate multicomponent mixtures of sodium polystyrene sulfonate (NaPSS) to further understand translational diffusion and formation of temporal aggregates observed in dynamic light scattering (DLS) of charged macromolecules. Mixtures consisted of fluorescein isothiocyanate labeled NaPSS probe and an unlabeled NaPSS matrix in salt concentrations that exceeded Cp/Cs=5.7. In an effort to entrain single polymers into temporal aggregates, the matrix concentration was increased for several molecular weight probe polymers. If dilute probes enter matrix polymer aggregates then probe diffusion would be dictated by the aggregate, independent of probe molecular weight. But measured self-diffusion depended on probe molecular weight, evidence against probe aggregate inclusion. Further, probe diffusion depended on matrix molecular weight, at least above the entanglement concentration, suggesting that probes do not become entrained in the temporal aggregates, but respond to the presence of matrix polymer. Diffusion in unimodal NaPSS systems obeyed theoretical scaling laws of D~C-0.5 but did not exhibit bi-exponential decay behavior as would be expected for diffusers in and outside temporary aggregates. |
Friday, March 6, 2020 12:15PM - 12:27PM |
X35.00006: Simulating Surface-Grafted Polymers in Solvent Mixtures: Effects of Cononsolvency Jing Zong, Dong Meng One puzzling phenomenon about polymer conformations in a mixture of solvents is the cononsolvency effect -- polymers in a good solvent undergo reentrant coil-to-globule-to-coil transition upon addition of a good cosolvent. Recent studies have suggested the generic nature of the cononsolvency effect independent of chemically specific details of the polymer and solvents. In this study, we first reinforce such claim by showing that a coarse-grained soft model frequently used in studying polymers is able to reproduce the reentrant transition at the single-chain level, provided that solvents are treated explicitly. In our Monte Carlo simulations, the coil-to-globule-to-coil transition occurs as the chemical potential of polymers in solution decreases upon increasing the cosolvent fraction, ruling out increasingly worse solvent quality as the cause of collapse. To further our microscopic understanding, we apply the soft model to studying conformational responses of surface-grafted polymers under the cononsolvency effect. By analyzing the inter-polymer density correlations, we illustrate the highly correlated nature of polymer clustering mediated by the cosolvents. Conformational responses of high grafting density brushes will also be discussed in the context of smart sensor surfaces. |
Friday, March 6, 2020 12:27PM - 12:39PM |
X35.00007: Humidity- and surfactant-accelerated aging in poly(vinyl alcohol)-based thin films Katarzyna Majerczak, Zhenyu Jason Zhang This work aims to understand how relative humidity (RH) and chemical composition influence the diffusion of guest molecules in formulated polymer films replicating packaging materials for detergent products. Surface morphology of thin poly(vinyl alcohol) films containing glycerol and surfactants of various headgroup chemistry was examined using Atomic Force Microscopy under controlled RH conditions (15% – 55% RH). Diffusion was found to be controlled by both surfactant “blooming” from the polymer matrix and RH, leading to changes in film morphology. Anionic surfactants bloomed in the films at low concentration (1 wt%) above a threshold of 35% RH. Higher concentrations (above 3 wt%) were required for blooming of cationic surfactant, while nonionic surfactants showed no changes in film morphology regardless of concentration or RH. It is likely that chemical compatibility and charge-pairing effects are the main driving forces for these changes. Increased RH and presence of glycerol could enhance the free volume within the polymer matrix, accelerating diffusion and therefore achieving equilibrium (surfactant blooming), as confirmed by Dynamic Vapour Sorption measurements. |
Friday, March 6, 2020 12:39PM - 12:51PM |
X35.00008: Polydispersity Correction to the Order-Disorder Transition of Symmetric Diblock Copolymers Melts James Willis, Mark W Matsen
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Friday, March 6, 2020 12:51PM - 1:03PM |
X35.00009: Thermodynamics of Binding of Charged Dendrimers to Graphene: Simulation and Theory Mounika Gosika, Swati Sen, Arindam Kundagrami, Prabal K Maiti The thermodynamics of the binding of a charged dendrimer [poly(amidoamine)] to an uncharged graphene sheet is investigated through simulations and a mean-field theory. A non-monotonicity that is observed in the degree of binding of the dendrimer as a function of pH is explained through potential of mean force (PMF) calculations and the Flory-Huggins-Debye-Huckle type mean field theory, by analyzing the electrostatic and non-electrostatic interactions between the pairs of dendrimer, graphene, and water molecules and ions. The simulation trends are satisfactorily reproduced by the theoretical results. In addition to the van der Waals interactions between the dendrimer and the graphene sheet, it is found that the presence of the solvent ions and counterions too has a major influence on these trends. |
Friday, March 6, 2020 1:03PM - 1:15PM |
X35.00010: Complex Viscosity of Helical and Doubly Helical Polymeric Liquids from General Rigid Bead-Rod Theory Jourdain Piette, A. Jeffrey Giacomin, Mona Kanso With general rigid bead-rod modelling, we recreate shapes of complex macromolecular structures with beads, by rigidly fixing bead positions relative to one another. General rigid-bead rod theory attributes the elasticity of polymeric liquids to the orientation that their macromolecules develop during flow. For oscillatory shear flow, the frequency dependencies of both parts of the complex viscosity are predicted correctly. In this paper, we use general rigid-bead rod theory for the most complex macromolecular architectures to date. We thus explore the role of helix geometry on the complex viscosity of a helical polymeric liquid. Specifically, we investigate the effects of helix radius, flight length, helix length and the number of beads per flight on the complex viscosity function, the fluid relaxation time, the zero-shear values of the steady shear viscosity and of the first normal stress coefficient. As a worked example, we examine specifically deoxyribonucleic acid (DNA). Using general rigid bead-rod theory, we dissect the DNA to see how the first helix, second helix, and then the base pairs, each contribute to the complex viscosity. We next explore the rheological implications of gene replication to find that the unzipping of DNA into a pair of single strands is viscostatic. |
Friday, March 6, 2020 1:15PM - 1:27PM |
X35.00011: The tail free discotic liquid crystal 1,2,3,4,7-pentrafluoro triphenylene: a study in structural variations Mitch Powers, Brett Ellman, John Portman, Zhe Li, Kunlun Wang, Parikshit Guragain, Robert J Twieg, Scott Bunge, Lewis L Sharpnack, Dena Mae Agra-Kooijman, Satyendra Kumar Discotic liquid crystals are disc shaped molecules that self assemble into long columns of cofacial molecules while still maintaining some liquid-like properties. They are typically formed by rigid aromatic molecular cores surrounded by a number of flexible tails. The tails play an important role, as they separate the columns and provide a source of entropy which inhibit crystallization. In this contribution, we describe a tail free discotic liquid crystal 1,2,3,4,7-pentafluorotriphenylene (7F-TFT). We will explore the nature of this tail free mesophase by comparing this compound with a number of closely related compounds based on tetrafluorotriphenylene. By varying the position and chemical species of the fifth substituent, we will see the effects that molecular structure have on this unusual mesogen. |
Friday, March 6, 2020 1:27PM - 1:39PM |
X35.00012: Effects of Boundary Conditions and Alignment Methods on Liquid Crystal Performance in Microwave Devices Jason Nobles, Olha Melnyk, Anatoliy Glushchenko, Robert Camley, Zbigniew J Celinski Microwave devices are ubiquitous in our daily lives; cell phones, satellite communications, automobile safety radars all depend on microwaves. We are working on a technology, a merger of microwave science with liquid crystal physics, that has the potential to revolutionize microwave technology by reducing the size and cost of these devices by a factor of 100. As part of this effort, we are investigating a variety of the techniques used to control the initial state of the liquid crystal in a device to determine the optimum method to use with this emerging microwave technology. From our work, we see that a treated thin film of polyimide provides the best results. However, our work also demonstrates that, if a specialized liquid crystal known as dual frequency liquid crystal is used, the initial state of the liquid crystal does not significantly impact the performance of the device. This discovery reduces the number of steps necessary to manufacture microwave devices, saves on chemical and treatment costs, and eliminates several manufacturing challenges unique to liquid crystal based microwave devices. These benefits add up to a significant savings in time and cost during the design and manufacture of microwave components based on liquid crystal technology. |
Friday, March 6, 2020 1:39PM - 1:51PM |
X35.00013: Fast Water Transport in Polyelectrolyte Brush Functionalized Nanochannels VISHAL SANKAR SIVASANKAR, Sai Ankit Etha, Harnoor Singh Sachar, Siddhartha Das The need for enhanced transport and enhanced separation in nanochannels is prevalent across disciplines of fluid mechanics, material science, bio-medicine, nanotechnology, etc. In this study, we show that the functionalization of nanochannel with pH-responsive polyelectrolyte (PE) brushes, which we model using newly formulated augmented Strong Stretching theory, can lead to fast electroosmotic (EOS) transport of water. We observe that the presence of PE brushes results in enhanced flux when compared to brush free nanochannel. This is because of the localization of the EDL charge density away from the flow retarding wall. The enhanced flux obtained in brush functionalized nanochannels tends to be comparable to graphene-based state-of-the-art nanostructures which indicate that such a system could be used for fast transport of water. Moreover, we also witness a large gradient in the flow profiles, for certain conditions of the solvent, which suggests that these brush functionalized nanochannels could also be useful in size-based separation of particles. |
Friday, March 6, 2020 1:51PM - 2:03PM |
X35.00014: Mechanisms of Surfactant Adsorption and Interfacial Tension Lowering for Enhanced Oil Recovery (EOR) Applications Jaeyub Chung, Bryan Boudouris, Elias I Franses The robust evaluation of aqueous surfactant formulations depend on their ability to lower the interfacial tensions (IFTs) of oil/water interfaces for mobilizing oil. For a formulation to be most effective, the IFT of an oil/water interface should be ultralow (<0.01 mN/m). We have discovered that there are two types of relevant equilibrium IFTs (EIFTs). The un-pre-equilibrated EIFT (EIFTup) is established when primarily the surfactants have equilibrated across the interface, and applies to the early stages of the EOR process. The pre-equilibrated EIFT (EIFTp) is established when the oil and aqueous components are also equilibrated, and is applied to the later stages. The two EIFTs can be different due to the preferential partitioning of the various surfactant components usually present in commercial surfactants. Such partitioning can change drastically the chemical potentials and the partition coefficients of these surfactant components, and causes an IFT shift to a more stable value as the oil and aqueous phases components equilibrate also at longer times. The results have significant implications for understanding the effect of the surfactant concentration and composition on the EIFT. |
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