Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session R34: Processing-Dependent Nanoscale Structures in Polymers and Predictive MethodsFocus
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Sponsoring Units: DPOLY DSOFT Chair: Michael Hore, Case Western Reserve University Room: 506 |
Thursday, March 5, 2020 8:00AM - 8:12AM |
R34.00001: Solvent-Non-Solvent Rapid Injection for the Preparation of Hierarchically Ordered Hydrogels Robert Hickey Non-solvent-induced phase separation is a non-equilibrium method used heavily in industry for fabricating separation membranes. The resulting microstructure forms when a homopolymer initially in a good solvent is immersed into a poor solvent, inducing polymer phase separation and forming a microporous membrane consisting of polymer-rich and non-solvent-rich regions. We recently showed that non-solvent-induced phase separation methods will produce hierarchically ordered physically crosslinked hydrogels when amphiphilic triblock copolymers are used instead of homopolymers. In our system, when triblock copolymers comprising of a hydrophobic-hydrophilic-hydrophobic chain sequence initially in a common solvent will rapidly self-assemble at the nano and microscale when injected into water. We have developed a universal and quantitative method for producing physically crosslinked hydrogels exhibiting tunable mechanical properties superior to typical physically crosslinked triblock copolymer hydrogels, and interesting structural color properties. At a fundamental level, the rapid injection process described here encompasses two self-assembly processes (microphase and macrophase separation), further increasing the tunable parameters for controlling material structure and property. |
Thursday, March 5, 2020 8:12AM - 8:24AM |
R34.00002: WITHDRAWN ABSTRACT
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Thursday, March 5, 2020 8:24AM - 8:36AM |
R34.00003: Understanding and controlling metal oxide growth within block copolymers Neta Shomrat, Inbal Weisbord, Rotem Azoulay, Barun Barick, Assaf Simon, Tamar Segal-Peretz In recent years, sequential infiltration synthesis (SIS) has emerged as a novel technique for growth of inorganic materials within block copolymers (BCP) and templating inorganic nanostructures from BCP due to SIS high growth rate and selectivity within polar BCP domains. However, to utilize SIS in a variety of BCP and in multiple length scales, there is high need for a full description of SIS mechanism. |
Thursday, March 5, 2020 8:36AM - 8:48AM |
R34.00004: Process-directed self-assembly: Do we understand the collective short-time dynamics in multicomponent polymer melts? Marcus Mueller Process-directed self-assembly refers to processes that reproducibly trap the kinetics of structure formation that ensues after a sudden change (“quench”) of the thermodynamic state into a desired, (meta)stable target state. This strategy benefits from specific advantages of copolymer systems, such as the rather comprehensive knowledge of equilibrium properties and the timescale separation between the quench of thermodynamic state variables, the spontaneous relaxation of the system towards the “nearest” metastable state, and the thermally activated escape from the metastable target state. Typically the relaxation from the unstable state occurs on a time scale that is comparable to the single-chain relaxation time. This short-time kinetics of structure evolution templates the morphology at later stages but poses challenges for a theoretical description. Examining simple, prototypical examples, we highlight the role of internal modes and indicate how dynamic SCFT can be generalized to include the consequences of the subdiffusive single-chain dynamics for the collective kinetics on times comparable to the Rouse-relaxation time. |
Thursday, March 5, 2020 8:48AM - 9:00AM |
R34.00005: Nonsolvent Induced Phase Separation in Polymer Droplets Douglas Tree, Rami Alhasan, Dakota Banks, Tanner Wilcoxson Nonsolvent induced phase separation (NIPS) occurs when a polymer solution is brought into contact with a miscible nonsolvent, leading to the precipitation of a polymer-rich phase. Because of its simplicity, NIPS processes are widely used to generate a variety of microstructures in polymer materials such as membranes and micro/nanoparticles. Despite its prevalence, predicting and controlling the microstructure generated by NIPS remains a difficult challenge, owing to the complex interactions between the diffusive transport, hydrodynamics and phase-separation kinetics in the process. In our approach, we use simulations of a phase-field model of a polymer solution to examine the effect of mass transfer, hydrodynamics and geometry on the formation of microstrucure. In particular, we study the NIPS process in polymer droplets, where we examine the effect of droplet size, shape, and composition on the resulting microstucture. We also examine the impact of finite solvent/nonsolvent miscibility on the kinetics and microstructure of the phase separation. |
Thursday, March 5, 2020 9:00AM - 9:12AM |
R34.00006: Arrested mobility and thermal fluctuation effects on the mass transfer induced phase separation of ternary polymer solutions Jan Ulric Garcia, Douglas Tree, Tatsuhiro Iwama, Kris T Delaney, Glenn H Fredrickson Many polymer membranes are made by immersion of a polymer solution film in a nonsolvent bath: the mass transfer exchange between the nonsolvent from the bath and the solvent in the film induces phase separation of the film into a polymer-rich phase that becomes the membrane matrix and a polymer-poor phase that becomes the membrane pores. Microstructure formation of these membranes is still not fully understood due to the nature of the physical processes involved: the mass transfer induced phase separation, the coarsening of domains, and the vitrification of the polymer-rich phase that arrests membrane microstructure. In this work, we use phase-field models of the ternary polymer-nonsolvent-solvent system to solve the coupled convection-diffusion and momentum equations that describe membrane formation. We model the glass transition using contrasts in the viscosity and mobility of the polymer-rich and polymer-poor phases. We report how glassy dynamics, and the inclusion of thermal fluctuations, contribute to microstructure formation. |
Thursday, March 5, 2020 9:12AM - 9:48AM |
R34.00007: Precision polymer nanoparticles Invited Speaker: Rachel O'Reilly Polymerization-induced self-assembly (PISA) is a versatile method to prepare nanoparticles of various morphology. Traditionally, nanoparticles are prepared via self-assembly of pre-formed polymers in H2O. Rigorous optimization is often required in these systems, involving iterative cycles of polymer synthesis, self-assembly, and evaluation of the self-assembled morphologies. PISA offers an elegant solution to the tedious procedures of conventional self-assembly by forming the particles in situ as the polymerization progresses. PISA involves chain-extension of a hydrophilic macroinitiator (or macro-chain-transfer agent) with monomers that are miscible with water, but form a hydrophobic, immiscible polymer, driving self-assembly. PISA can be conducted at high solids contents under a wide variety of reaction conditions (i.e., low or high temperature, variable solvent mixtures, or in the presence of drugs or biomacromolecules). However, monomers which can be utilized in PISA are often difficult to identify from their chemical structures alone, and experiments are often necessary to determine their usefulness in PISA. We have been developing synthetic methods and developing predictive tools to expand the scope of PISA and also show its application in the design of functional materials. |
Thursday, March 5, 2020 9:48AM - 10:00AM |
R34.00008: Molecular Modeling of Poly(methylmethacrylate-block-acrylonitrile) as Precursors of Porous Carbon Fibers Xi Ryan Hao, Joel M. Serrano, Tianyu Liu, Assad Ullah Khan, Brandon Botset, Benjamin J. Stovall, Zhen Xu, Dong Guo, Ke Cao, Guoliang Liu, Shengfeng Cheng Porous carbon fibers (PCFs) based on block copolymers exhibit well-controlled hierarchical porous structures and high specific interfacial areas, which lead to excellent electrochemical properties. Understanding the conformation and morphology of polymer precursors before conversion is crucial for designing and optimizing PCFs. To expedite materials discovery, we perform molecular dynamic simulations for a series of poly(methylmethacrylate-block-acrylonitrile) (PMMA-b-PAN) with various block molecular weights and develop a model to characterize the morphology and compute the interfacial area of PMMA-b-PAN melts. We build both laminar and disordered phase of PMMA-b-PAN melts with an atomistic model of the polymer. For the disordered melts, our results show that the interfacial area is maximized when the volume fraction of either block is close to 50%, consistent with experimental results. The stability of the laminar phase is probed by performing thermal annealing on the systems and the conversion to a disordered phase is realized by introducing extra attractions between PAN blocks, which mimic the cross-linking reactions of PAN blocks in experiments. Our models pave the way of optimizing PCFs by designing PMMA-b-PAN precursors in silico. |
Thursday, March 5, 2020 10:00AM - 10:12AM |
R34.00009: Phase diagram for diblock copolymer melts from Langevin field-theoretic simulations Tom Beardsley, Mark W Matsen Field-theoretic simulations (FTS) provide fluctuation corrections to self-consistent field theory (SCFT) by simulating its field-theoretic Hamiltonian rather than applying the saddle-point approximation. Here, we apply Langevin FTS (L-FTS) to AB diblock copolymer melts, where the composition field fluctuates via Langevin dynamics but the saddle-point approximation is still applied to the pressure field that enforces incompressibility. The method is demonstrated to be one or two orders of magnitude faster than previous Monte Carlo simulations (MC-FTS), permitting the rapid formation of spontaneously ordered configurations and the accurate determination of their order-disorder transitions. The results are used to construct a phase diagram for diblock copolymer melts of high invariant polymerization index, N = 104. |
Thursday, March 5, 2020 10:12AM - 10:24AM |
R34.00010: Entanglements in block copolymers self-assembled into lamellae morphology Nicolas Garcia, Jean-Louis BARRAT Understand the viscoelastic behavior of polymers is of fundamental interest but also is relevant to consider their technological applications. It is well-known that the mechanical properties of polymers depend fundamentally on the molecular chain weight. The main effect of increasing weight is the arise of entanglements. |
Thursday, March 5, 2020 10:24AM - 10:36AM |
R34.00011: Systematic construction of the dynamic density functional theory for inhomogeneous polymer systems Sriteja Mantha, Friederike Schmid Time scales predicted by the dynamic density functional theory (DDFT) for an inhomogeneous polymer system are far from accurate. One of the main reasons for this is, approximate local and non-local schemes employed to compute the mobility coefficient,Λαβ(r,r') . In the DDFT calculations,Λαβ(r,r'), relates the thermodynamic driving force due to the monomer β at r' to the current of the monomer α at r . In this talk, we will put forward a physically motivated approach to compute the Λαβ(r,r') with the objective to improve the DDFT predictions. We compute the Λαβ(r,r') from the relaxation time of the single chain dynamic structure factor. We find that the Λαβ(r,r') obtained from such an approach captures both the global dynamics and the effective local rearrangements of the chain at relevant length scales. Using this scheme, we conduct DDFT calculations to study two related problems. One is the formation of the lamellar morphology in a symmetric diblock copolymer system starting from a homogeneously dispersed state, and the other is the relaxation of the lamellar morphology into a homogeneously dispersed state. We show that the DDFT predictions for the above problems are in reasonably good agreement with the corresponding fine-grained simulations. |
Thursday, March 5, 2020 10:36AM - 10:48AM |
R34.00012: Spectrally-Accurate Linear-Scaling Self Consistent Field Theory and Applications Daniel Vigil, Carlos J Garcia-Cervera, Kris T Delaney, Glenn H Fredrickson We present a new algorithm for numerical polymer self-consistent field theory (SCFT) that has spectral accuracy in the contour dimension while maintaining near-linear computational cost scaling with number of contour sample points, which no other reported algorithm achieves. The new algorithm is enabled by using a coherent states (CS) model of the polymer field theory, which replaces the chain propagator objects from auxiliary field (AF) models with fields that generate chain statistics. We also show that the newly reported algorithm is compatible with a variety of AF algorithms, but can replace their propagator algorithms with our linear-scaling spectrally accurate algorithm. Applications enabled by this new algorithm are presented. |
Thursday, March 5, 2020 10:48AM - 11:00AM |
R34.00013: Open-source SCFT on graphics processing units Guo Kang Cheong, Anshul Chawla, David Clark Morse, Kevin D Dorfman Self-consistent field theory provides an effective framework for materials discovery, allowing one to target particular morphologies by rapid examination of their phase space. We present a GPU-accelerated self-consistent field solver parallel to the open-source Polymer Self-Consistent Field (PSCF) codebase. The codebase is built from the ground up to utilize highly efficient GPU-acceleration yet remains backwards-compatible with PSCF. Our testing shows up to 60x acceleration in computing time for the largest problems. Improvement in open-source tools enables new opportunities by the community to pursue various problems of interest such as the inverse design of the bulk phases. Increasingly, speed becomes vital in such problems especially in an era of data and machine learning where the manipulation of large data sets is key to the understanding of fundamental polymer physics. |
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