Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session X32: Dynamics and Thermodynamics of Polymer Blends and Solutions in the Bulk and near Hard Surfaces |
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Sponsoring Units: DPOLY Chair: Qiang Wang, Colorado State University Room: 504 |
Friday, March 6, 2020 11:15AM - 11:27AM |
X32.00001: Influence of polymer structure on adsorption onto metal surfaces Christopher O'Bryan, Olekandra Zavgorodnya, Russell Composto, Daeyeon Lee In mineral processing, the separation of a desired mineral ore from the gangue minerals is often achieved through froth flotation. Hydrophobic particles are collected by air bubbles passing through a slurry of the raw minerals to form a froth on the surface for harvesting. Often, modifications of the material’s hydrophobicity are necessary to avoid flotation of an unwanted mineral and to prevent harmful particle interactions; water-soluble molecules are commonly added to the mineral slurry to alter the wettability of mineral surfaces and change particle-bubble interactions. The effectiveness of these additives depends on the surface coverage, layer thickness, and rigidity of the adsorbed polymer layer. Particularly in the case of polymeric additives, how their structure relates to their adsorption behavior is far from understood. Here, we investigate the role of polymer structure on their adsorption behavior onto metal surfaces and present our preliminary findings. |
Friday, March 6, 2020 11:27AM - 11:39AM |
X32.00002: Nitroxide Radical Polymer-Solvent Interactions and Solubility Parameter Determination Alexandra Easley, Lillian Vukin, Dylan Howard, Jose L Pena, Jodie Lutkenhaus Nitroxide radical polymers such as poly(2,2,6,6-tetramethylpiperidinyloxy-4-ylmethacrylate) (PTMA) are electrode materials of interest for organic batteries. They exhibit a reversible capacity (111 mAh/g theoretical), high redox potential (3.6 V vs Li/Li+), and rapid charging. One major consideration for the design and processing of organic batteries is the interaction between the polymer and solvent, such as the electrolyte. For example, linear PTMA may dissolve in the electrolyte solution, which leads to capacity fade during long-term cycling. To predict these polymer-solvent interactions, the Flory-Huggins interaction parameter, the Hildebrand and Hansen solubility parameters of PTMA are determined using group contribution calculations and experimental methods. Using calculated and measured solubility parameters, the Flory-Huggins interaction parameter for PTMA is estimated for common battery electrolyte systems. Membrane osmometry is used to confirm the PTMA Flory-Huggins interaction parameter. Once confirmed, the PTMA Flory-Huggins interaction equation is used to recommend new electrolyte solvents to improve battery performance. |
Friday, March 6, 2020 11:39AM - 11:51AM |
X32.00003: Shape Engineering of Monodispersed Cone-Shaped Particles by Tuning Blend Structure of AB Diblock Copolymer and C-Type Copolymer within Emulsion Eun Ji Kim, Jae Man Shin, Kang Hee Ku, YongJoo Kim, Hongseok Yun, Bumjoon Kim Precise control of the shape and nanostructure of block copolymer (BCP) particles are of great interest for their shape-dependent physical properties. Here, we exploit the blend of poly(styrene-block-1,4-butadiene) (PS-b-PB) BCP and poly(methylmethacrylate-statistical-(4-acryloylbenzophenone)) (P(MMA-stat-4ABP)) sCP within the colloidal confinements to develop a series of particles with different symmetry. The key strategy for tuning the particle shape is to systematically control the incompatibility between the BCP and sCP by varying the mole fraction of 4ABP in sCPs (Φ4ABP) and the volumetric ratio of sCPs in total blend (fsCP). The particles were produced by membrane emulsification method to have monodisperse particle size and shape, and the particle shape can be tuned sequentially from striped ellipsoid to Janus-sphere, to cone-shaped with the increase of Φ4ABP and fsCP. In particular, the shape-anisotropy of cone-shaped particles was systematically controlled by varying the size and Janusity, which is supported by quantitative calculation from the modified theoretical model. Furthermore, the importance of the shape control of monodispersed cone-shaped particles was demonstrated by investigating the colloidal coating property of these particles. |
Friday, March 6, 2020 11:51AM - 12:03PM |
X32.00004: Aqueous Solution Behavior of Poly(ethylene oxide) in Presence of Complex Ions David Hoagland, Satyam Srivastava, Zachary Fink, Elizabeth Burns Poly(ethylene oxide) (PEO) in aqueous solutions has often been studied by experiment and modeling, but despite widespread use, questions about solution properties remain. Motivated by PEO’s potential to reduce CO2 emissions as a strength-building concrete additive, chain conformation was examined in solutions containing complex ions present during concrete curing. Ion-induced changes for linear 100,000 g/mol PEO were mostly unremarkable and consistent with past reports, the hydrodynamic radius by dynamic light scattering or intrinsic viscosity depressed slightly as ion concentration grows. Trends for aluminum-containing ions [at neutral and basic pH monovalent anion Al(OH)4 predominates] were different, with radius by dynamic light scattering approximately 50% larger than by intrinsic viscosity. We hypothesize weak ion-mediated coupling between hydroxyl end groups disruptable by shearing. In support, hydrodynamic radius by dynamic light scattering fell to the value by intrinsic viscosity when hydroxyl end groups were converted to methoxy end groups. The chemistry of the ion-induced chain association remains unclear. |
Friday, March 6, 2020 12:03PM - 12:15PM |
X32.00005: Quantitatively Determining of Population Ratios in Bimodal Polymeric Solutions by Neutron Scattering GUAN-RONG HUANG, Kunlun Hong, Chi-Huan Tung, Dongsook Chang, Christopher N Lam, Changwoo Do, Yuya Shinohara, Shou-Yi Chang, Yangyang Wang, Wei-Ren Chen Association of amphiphilic polymers in aqueous solutions is of fundamental importance. The coexistence of unimers and aggregates over a broad range of phase regions has been widely reported. Although scattering technique has been employed to identify the structure of micellar aggregates and free unimers as well as its time-evolution processes, the determination of their relative population of unimer and aggregate itself is still challenging. Here, using small angle neutron scattering, we present a comprehensive SANS study of n-dodecyl-PNIPAm. By adjusting the deuterium/hydrogen ratio of water, the intra-micellar polymer and water distributions are obtained. The micellar aggregation number and number density are further determined. Most importantly, the distributions of unimers and micellar aggregations at different temperatures are obtained quantitatively for the first time. |
Friday, March 6, 2020 12:15PM - 12:27PM |
X32.00006: Role of Miscibility in the Shape Memory Properties of Polymer Blends Surbhi Khewle, Pratyush Dayal Shape Memory Polymers(SMPs) are smart materials capable of transforming back to their intended shape and therefore, are used to replicate biomimetic functionalities in artificial materials. Here, we demonstrate that unlike chemical synthesis, polymer blending can be used as an effective technique to design SMPs. In our work, we consider partially miscible crystalline and amorphous polymer blends, to represent the hard and soft segments of SMPs, respectively. To determine the miscibility of blend we construct equilibrium phase diagram by combining Flory-Huggins and phase-field theories that account for both, amorphous-amorphous and crystal-amorphous interactions. We incorporate the effect of these interactions into standard viscoelastic model and determine thermo-mechanical behaviour of SMP blend, using composition dependent viscoelastic properties calculated from Equivalent Box Model. Finally, via simulations, we determine shape fixity and recovery ratios and demonstrate that our calculations are in excellent agreement with the experimental results for PCL-SBS blends. We believe that our findings can not only be utilized to design SMP blends with tailored properties but also be used to establish their structure-property relationships. |
Friday, March 6, 2020 12:27PM - 12:39PM |
X32.00007: Dynamic interfacial trapping of Janus nanorod aggregates in polymer blends Felipe Leis Paiva, Michael Hore, Argimiro Secchi, Veronica Calado, Joao M Maia, Shaghayegh Khani Taking advantage of both shape and chemical anisotropy on the same nanoparticle offers rich plasmonic and self-assembly possibilities for nanotechnology. Combining Dissipative Particle Dynamics and Discrete Dipole Approximation calculations, the directed assembly of Janus nanorod aggregates in polymer blends has been assessed, along with the optical properties resulting thereof. Janus rods become kinetically-trapped and exhibit either parallel or antiparallel alignment with respect to their long axis. This depends on several factors that can be precisely tuned. Ultimately, two different aggregate structures result from rod tumbling that are not observed under quiescent conditions: monolayer-like aggregates exhibiting trapped rods with antiparallel configuration; and stacked nanorod arrays similar to superlattice sheets. Hence, the present study offers fundamental insight into relevant parameters governing the directed assembly of Janus nanoparticles at an interfacial level as well as an assessment of the potentially novel optical applications deriving from the resulting aggregate structures, such as peculiar displays and sensors. |
Friday, March 6, 2020 12:39PM - 12:51PM |
X32.00008: Title: Tuning Diblock Copolymer Micelles by Cosolvent Effects: A Simulation Study Dong Meng, Jing Zong A powerful method to manipulate the micellar structures formed by amphiphilic diblock copolymers (DBC) in a selective solvent is by addition of a cosolvent. Unlike the single-solvent case, few simulation studies on DBC micellization in solvent mixtures has been reported due to high computational cost associated with the necessity of treating solvents explicitly. Here, the Field-Accelerated Monte Carlo simulation is employed for the task under the expanded grand canonical ensemble. We investigate the effects of introducing a cosolvent on the critical micelle concentration, micellar morphology, and aggregation number. Specifically, we consider two types of solvent pair: interacting-solvent and cononsolvent pairs. It is found that the interacting-solvent pair promotes morphology transition from micelles to vesicles. In the case of cononsolvent pair with respect to the corona block, aggregation number of micelles increases significantly as the result of maximizing contact between polymers and the minor amount of cosolvent. Our study reveals the competing and cooperative interplays of solvent pairs in determining the DBC micellar structures, pointing out the necessity of considering solvent explicitly in simulations as oppose to the conventional "effective-single-solvent" approach. |
Friday, March 6, 2020 12:51PM - 1:03PM |
X32.00009: Efficient sampling of polymer conformations using Brownian Bridges Vivek Narsimhan, Shiyan WANG, Doraiswami Ramkrishna In this talk, we introduce a mathematical concept known as a stochastic bridge, and describe how it can be utilized in many areas of polymer physics. A stochastic bridge is a random process whose start and end regions in phase space are specified. Such processes naturally find utility in situations when one wants to sample polymer conformations with a given topology and/or energy. In the first part of the talk, we expand upon our previous work and discuss how one can systematically generate bridge processes for continuous polymer chains described by a stochastic differential equation. We will then discuss how to use such ideas to generate polymer conformations of a given topology (e.g., rings, polymers with fixed winding or twist, etc.). We will then study a canonical problem – a polymer under an external field – and show how a bridge formulation allows one to exactly sample polymer conformations in a given range of total energy. This methodology thus allows one to sample rare events (i.e., high energy) efficiently, or conversely most probable configurations (i.e., low energy). We will conclude on how to scale these ideas to larger dimensional systems, and discuss some advantages and disadvantages of using bridge processes compared to other biased sampling strategies |
Friday, March 6, 2020 1:03PM - 1:15PM |
X32.00010: Investigation of polymer diffusion in confined geometries using differential dynamic microscopy techniques Emmanuel Hitimana, Sveta Morozova The fundamental understanding of polymer diffusion in confined geometries is important for industrial as well as broader applications such as transport in cell-like environments, improved drug delivery, and filtration. However, the study of polymer diffusion in such environments is often challenging due to the nanometer size scales of polymers and to the inhomogeneous geometry of the landscape. We have developed differential dynamic microscopy (DDM) techniques to investigate the dynamics of fluorescein tagged poly-l-lysine chains in confined environments in any arbitrary direction along textured surfaces. Using a curved surface, we can control the local confinement. The role of polymer molecular weight, concentration, confinement, and local geometry on polymers dynamics will be discussed. |
Friday, March 6, 2020 1:15PM - 1:27PM |
X32.00011: Direct visualization of branched polymer dynamics using single molecule studies Shivani Patel, Charles M Schroeder We study the dynamics of single branched polymers in dilute and non-dilute solutions using single-molecule fluorescence microscopy. In particular, we use a hybrid enzymatic-synthetic approach to synthesize DNA-based branched polymers such as comb polymers that contain a long backbone with multiple side branches grafted at various positions. Following synthesis, we directly study the dynamics of single branched polymers, particularly in non-dilute solutions in extensional flow, and compare them to the dynamics of linear polymers. We further study the effects of background concentration and polymer topology on branched polymer dynamics in order to elucidate the non-equilibrium behavior of topologically complex polymers. For instance, our work on comb polymer dynamics has shown that contrary to dilute solutions and melts, the addition of branches on to a linear backbone speeds up the relaxation of comb polymers compared to their linear analogs in semi-dilute solutions. Overall, our work shows that single polymer dynamics can be used to provide a direct link between polymer microstructure and bulk rheological properties. |
Friday, March 6, 2020 1:27PM - 1:39PM |
X32.00012: Additive Driven Morphological Transition of Block Copolymer Particles: Elongation, Transformation and Disassembly of Single Domain Seonghan Lee, Jae Man Shin, Kang Hee Ku, Bumjoon Kim Particles with controllable shape and internal morphology received great attention as a promising colloidal material. Here we report co-assembly of polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) diblock copolymer (BCP) and bromoalkyl based small molecule additives confined in evaporative emulsion droplet. The presence of additives with varying volume fraction (φ) resulted in (1) significant increase of aspect ratio of prolate particles from 2.4 to 4.5 (φ<0.40), (2) unique transformation of domain structure from conventional lamellar stacks into spherical shaped, multi-layered lamellar (0.40<φ<0.45), and (3) disassembly of single lamellar domains into micellar spheres (0.45<φ). Investigation on the morphological evolution of particle demonstrated that the favorable interaction with P2VP and bromine-containing additives allows quaternization and significant swelling of P2VP domains, which is further assisted with the presence of external aqueous phase. This additive induced morphological transformation was further systematically controlled by incorporation various types of additives to achieve control over the degree of P2VP domain swelling. |
Friday, March 6, 2020 1:39PM - 1:51PM |
X32.00013: Single molecule visualization of single ring polymers in the flow-gradient plane of shear flow Michael Tu, Rae M Robertson-Anderson, Charles M Schroeder The lack of free ends on ring polymers yields a unique topology that has fascinated polymer physicists and chemists for decades. Despite recent progress, we still lack a clear understanding of the molecular-level dynamics of ring polymers. Here, we use single-molecule imaging to directly visualize individual ring polymers in shear flow. We have built a custom shear flow apparatus to be used in conjunction with single-molecule fluorescence microscopy to study the dynamics of individual ring polymers in the flow-gradient shear flow. Using this device, we are able to characterize the fractional extension and orientation angle of ring polymers under steady shear, and compare the responses to their linear counterparts. We report the steady-shear fractional extension, orientation angle, and temporal-averaged spatial conformations of ring polymers in shear flow as a function of the applied dimensionless flow strength (Wi, Weissenberg number), and compare the results to their linear polymer counterparts. We also report observations of tumbling and tank-treading-like behavior of ring polymers in shear flow. Overall, these results provide new molecular-level insights into the dynamics of ring polymers in flow. |
Friday, March 6, 2020 1:51PM - 2:03PM |
X32.00014: Phase behavior of diblock copolymer-homopolymer ternary blends containing an asymmetric diblock copolymer Bo Zhang, Shuyi Xie, Frank S Bates, Timothy Lodge Lifshitz points (LPs) are predicted to exist in symmetric A/B/A-B ternary blends in the mean-field limit, where A and B are homopolymers and A-B is the corresponding diblock copolymer. At finite molecular weights, the LP is replaced by a channel of bicontinuous microemulsion (BμE) due to fluctuation effects. A recent study of symmetric ternary blends, where A is poly(cyclohexylethylene) (PCHE) and B is poly(ethylene) (PE), demonstrated that the BμE is bracketed by a line of congruent lamellar-disorder transitions and a Scott line of critical points, at homopolymer content near the predicted LP value. In this work, we investigated the phase behavior of a similar PCHE/PE/PCHE-PE ternary blend but with a compositionally asymmetric diblock copolymer. The phase behavior, which was determined using small angle X-ray and neutron scattering and optical transmittance measurements, revealed that the line of congruent transitions is decoupled in composition from the line of critical points. Additionally, a wide range of phase space between the compositions associated with the congruent condition and Scott line was identified as containing the BμE morphology. |
Friday, March 6, 2020 2:03PM - 2:15PM |
X32.00015: 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 (Zhang, P.; Wang, Q. Soft Matter, 2015, 11, 862), 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 (Obukhov, S. P.; Semenov, A. N. Phys. Rev. Lett. 2005, 95, 038305), which is about one order of magnitude stronger than that due solely to the finite chain length given by the SCF theory. |
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