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 X63: Self-Assembly in Diblock and Triblock CopolymersLive
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Sponsoring Units: DPOLY Chair: Robert Hoy, Univ of South Florida |
Friday, March 19, 2021 8:00AM - 8:12AM Live |
X63.00001: Dynamic Simulations of the "Bricks-and-Mortar" Mesophase in Miktoarm Block Copolymer/Homopolymer Blends Cody Bezik, Abelardo Ramirez-Hernandez, Juan De Pablo A new mesophase in binary blends of A-b-(B-b-A')n miktoarm star block copolymers and A homopolymers has recently been discovered experimentally and explored with field theoretic simulations. This mesophase consists of aperiodic discrete domains of A embedded in a continuous matrix of B up to extremely high concentrations of homopolymers. We investigate the structural and dynamic properties of the phase, including its linear rheological behavior, response to shear, and response to uniaxial tension using three-dimensional particle-based simulations. We highlight the role of molecular bridging on dominating the mechanical properties of the phase, as well as the unique response of the mesophase to shear, including the evident destruction of the bricks-and-mortar phase upon the application of shear. |
Friday, March 19, 2021 8:12AM - 8:24AM Live |
X63.00002: Atomistic and Systematic Coarse-Grained Models of Polybutadiene Copolymers with Various Microstructure Anastassia Rissanou, Antonis Chazirakis, Manolis Doxastakis, Patrycja Polinska, Craig Burkhart, Vagelis Harmandaris The current study focuses on the development of rigorous coarse-grained (CG) models for specific microstructures of polybutadiene (PB) systems. Atomistic Molecular Dynamics simulations for different stereo-chemistries of PB (1,4cis PB; 1,4tarns PB; 1,2vinyl PB) were executed. A complete validation of the atomistic model was performed by comparing its predictions on the structural and dynamical properties of bulk PB with available experimental data. Then, a database (library) of CG interaction potentials was developed using the atomistic data via the Iterative Boltzmann Procedure. The CG potentials database involves several interaction terms: (a) two-body (CG bonds), (b) three-body (CG angles), four-body (CG dihedrals), and (d) pair CG non-bonded contributions. The library includes terms for all PB stereo-chemistries. The transferability of the CG model in terms of both molecular weight and stereo-chemistry (from stereo-regular PB melts to copolymers of various cis:trans:vinyl compositions) is thoroughly examined. Using the new CG PB potential, simulations of high molecular weight PB copolymers with various microstructures are performed and their properties are predicted as a function of the microstructure composition. |
Friday, March 19, 2021 8:24AM - 8:36AM Live |
X63.00003: Hybrid particle-field simulations of polymer-grafted nanoparticles in block copolymer melts Daniil Bochkov, Frederic Gibou Modelling of the co-assembly of block copolymers and polymer-grafted nanoparticles within Self-Consistent Field Theory (SCFT) is challenging due to several aspects: the complex geometry of interparticle space, singularities in the pressure field on grafting surfaces, and the difficulty of finding the system's minimum energy. In this talk we present a hybrid particle-field approach for simulating grafted particles of arbitrary shapes in which the particles' boundaries are treated sharply without invoking any simplifying diffuse-interface approximations. We, first, show that the standard system of SCFT equations for grafted polymer chains is formally inconsistent and derive an equivalent one that does not lead to singularities in the pressure field. Second, we analytically derive the full derivatives of the system's energy with respect to positions and orientations of particles. Finally, the necessary PDEs are accurately and efficiently solved using a combination of an implicit geometry description, adaptive mesh refinement, and a specialized finite volume approach for imposing boundary conditions in complex geometries. To demonstrate the capabilities of the proposed approach we present simulations of the co-assembly of grafted Janus nanorods and diblock copolymers. |
Friday, March 19, 2021 8:36AM - 8:48AM Live |
X63.00004: Simple and Accurate Calibration of the Flory-Huggins Interaction Parameter James Willis, Tom Beardsley, Mark W Matsen
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Friday, March 19, 2021 8:48AM - 9:00AM Live |
X63.00005: Order-disorder transition for diblock copolymer melts using 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 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 order-disorder transition for diblock copolymer melts is evaluated for a high invariant polymerization index of N = 104. Consistent with experiment, we find direct transitions between disorder and gyroid and between disorder and Fddd. |
Friday, March 19, 2021 9:00AM - 9:12AM Live |
X63.00006: Effect of Block Copolymers on the Printability of Epoxy Inks for Direct Ink Writing Daniel Krogstad, Rishabh Ekbote, Deborah Liu, Gavin Donley, Simon Rogers Direct ink writing (DIW) is a highly versatile additive manufacturing technique that is applicable for a wide range of materials. The primary determination of the printability is based on the materials rheological properties. However, for nanostructured inks, the rheological characterization can be quite complex. Our work has shown that characterization of block copolymer (BCP) containing epoxy inks show no obvious difference in their rheological properties using traditional oscillatory amplitude sweeps as a function of the BCP concentration. However, significant differences are observed during printing. Instead, transient creep testing is used to show that the BCP containing inks had a lower apparent yield stress and a lower time-dependent decrease in the shear rate as compared to the base epoxy ink, which correlate well will with the printing results The creep testing also can be used to identify the time-dependent behavior of these inks, and identify pressures in which the inks will “clog” during printing, even if they initially print well. This work shows that the nanostructure of printable inks can result in complex rheological behavior, but we have identified transient creep testing as an effective way to characterize the printability of these nanostructured inks. |
Friday, March 19, 2021 9:12AM - 9:24AM Live |
X63.00007: Anomalous molecular-weight dependence of aqueous polypropylene glycol in swelling of amphiphilic norbornene copolymers containing hexafluoroisopropanol Siyuan Li, Bryan D Vogt Polymer membranes offer a low-cost path to separate bio-products. Amphiphilic polyol, commonly used as surfactant in fermentation process to suppress foaming, can severely swell membrane to a degraded performance. Here we systematically investigate the role of hydrophobicity and molecular mass (Mn) of the polyol using quartz crystal microbalance with dissipation (QCM-D) to quantify the swelling and rheological properties. We examined Mn-dependent sorption behavior of polyethylene glycol (PEG) and polypropylene glycol (PPG) at 10 ppm in aqueous solution for a series of norbornene copolymers containing approximately 50 mol% hexafluoroisopropanol (HFA) and 50 mol% alkyl (methyl to decyl). The alkyl chain length did not dramatically influence the swelling. We attribute this to the swelling driven by hydrogen bonding between hydroxy groups on the polyol and HFA group. The swelling by PEG in solution is nearly invariant with Mn and is significantly less than the swelling by the higher Mn PPG. A maximum in swelling is observed at Mn=3kg/mol for the PPG with the swelling dramatically decreasing for higher and lower Mn PPG. This strong Mn-dependence of the swelling may provide a potential route to mitigate these effects through selection of the size of polyols. |
Friday, March 19, 2021 9:24AM - 9:36AM Live |
X63.00008: Molecule-microstructure-property relation of reversible soft materials self-assembled by bottlebrush-based triblock copolymers Shifeng Nian, Zihao Gong, Guillaume Freychet, Mikhail Zhernenkov, Liheng Cai Linear-bottlebrush-linear (LBBL) triblock copolymers can self-assemble to reversible, unentangled, and solvent-free networks with elasticity orders of magnitude lower than that of conventional elastomers. The self-assembly depends on molecular architecture but remains poorly explored. We synthesize poly(benzyl methacrylate)-bottlebrush poly(dimethylsiloxane)-poly(benzyl methacrylate) (PBnMA-bbPDMS-PBnMA) with controlled PBnMA weight fraction f and bottlebrush flexibility κ. At f<0.06, LBBL polymers form a disordered sphere phase regardless of the bottlebrush flexibility; this is in stark contrast to classical stiff rod-flexible linear block copolymers that are prone to form highly ordered nanostructures such as lamellae. For a semiflexible bottlebrush with κ~1, the self-assembled microstructure transitions from sphere to cylinder to lamellae as f increases from 0.04 to 0.48, but with the crossover f values much smaller than existing theoretical predictions. Remarkably, the network shear modulus increases exponentially with f for the cylinder phase but becomes saturated around 100 kPa for the lamellae phase. Our results establish the previously unexplored molecule-microstructure-property relation of bottlebrush-based triblock copolymers. |
Friday, March 19, 2021 9:36AM - 9:48AM Live |
X63.00009: Theory of microphase separation and micellization in solutions of intrinsically disordered proteins Siao-Fong Li, Murugappan Muthukumar We have formulated a theory of micellization and microphase separation in aqueous solutions of intrinsically disordered proteins, using self-consistent field theory and scaling arguments. The size and shape of micelles and critical micelle concentration will be presented for dilute solutions. For the case of microphase separation at higher protein concentrations, order-disorder transition, order-order transitions, and the dependence of domain sizes on protein sequence will be presented. |
Friday, March 19, 2021 9:48AM - 10:00AM Live |
X63.00010: Block copolymer-metal oxide nanocomposite via sequential infiltration synthesis Tamar Segal-Peretz Sequential infiltration synthesis (SIS) is an emerging method for growth of inorganic materials within polymers using atomic layer deposition chemistry. In SIS, vapor precursors diffuse into the polymer volume and interact with polymer moieties, forming hybrid organic-inorganic materials at the molecular level. We shed light on the dynamics and thermodynamics of AlOx and ZnO SIS in polymethyl methacrylate (PMMA), poly 2-vinylpiridine (P2VP) and their corresponding polystyrenes block copolymers using quantum mechanical calculations, microgravimetric measurements and high-resolution electron microscopy. We demonstrate block copolymer-metal oxide nanocomposite utilization in patterning, porous particle fabrication and tuned mechanical properties. |
Friday, March 19, 2021 10:00AM - 10:12AM Live |
X63.00011: Template-free alignment of lamellar block copolymers for large area sub-10 nm patterning Maninderjeet Singh, Chenhui Zhu, Joseph Walter Strzalka, Jack Douglas, Alamgir Karim The ever-increasing demand for powerful computing devices necessitates innovative lithographic solutions for increasing the number density of patternable features for use in integrated circuits. Block Copolymer (BCP) self-assembly in thin films offers a promising alternative for patterning sub-10 nm features in the sub-optical lithographic resolution with reduced complexity. Traditionally, BCP alignment for patterning has been achieved using lithographically defined templates. However, the template-free alignment of BCPs for sub-10 nm patterning has not been achieved to date despite the research efforts for the past 2 decades. In this work, we show the template-free alignment of lamellar BCPs for sub-10 nm patterning over large areas. We use thermal shear stress generated by a conformal elastomer during the thermal gradient-based annealing for the self-assembly and the alignment of the vertically oriented lamellar BCPs confined between neutral substrate and topcoat. Furthermore, we use these aligned BCP templates to generate large area aligned gold nanowires having tunable dimensions by a solution-phase infiltration method and BCP template removal. |
Friday, March 19, 2021 10:12AM - 10:24AM On Demand |
X63.00012: Synthesis and Self-assembly of Saccharide-Containing Triblock Copolymers Minji Seo, Sheng Li Hybrid block copolymers containing both oligosaccharide and synthetic polymer components have attracted much interest as sustainable material alternatives. In particular block copolymers containing small saccharide units such as mono-, di-, and tri-saccharides are capable of microphase separation to form regular domain morphologies despite their small molecular weights. In this contribute, we report the synthesis and morphology characterization of ABA-type triblock copolymers containing polystyrene (PS) as the synthetic mid-block and different saccharide molecules as end blocks. The triblocks were synthesized via copper(I)-catalyzed 1,3-dipolar azide-alkyne cycloaddition of alkyne-functionalized saccharides and difunctional azido-PS. The polymer bulk morphologies were then examined by a combination of small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). For triblocks containing maltotriose, they were found to self-assemble to form well-ordered sphere and cylinder morphologies with sub-10nm domain periodicity. For triblocks containing even smaller maltose units as the end blocks, microphase separation was also confirmed. However, the long-range order of the microdomains was compromised due to the low degradation temperature of the saccharide blocks. |
Friday, March 19, 2021 10:24AM - 10:36AM Live |
X63.00013: Periodicity and Order Parameter of Hexagonally Packed Cylindrical Phase in a Periodic Box Yuan Feng, Jiaping Wu, Baohui Li, Qiang Wang In molecular simulations of self-assembled periodic structures (e.g., those formed by block copolymers), the periodic boundary conditions (PBCs) of the simulation box limit the periodicity (thus the orientation) of the periodic structures to discrete values that are commensurate with the periodicity of the box. For the most commonly used orthorhombic simulation boxes, while the case of cubic phases (e.g., the body-centered cubic spheres or the double gyroid) is straightforward to analyze and one of us proposed a general formula to calculate the lamellar period, the periodicity of hexagonally packed cylindrical phase has only been analyzed by one of us in a few special cases (Macromolecules 34, 3458 (2001); J. Chem. Phys. 138, 194904 (2013)). Here we propose a general method for calculating the periodicity of the cylindrical phase in an orthorhombic box. Based on this, we further propose an order parameter of the cylindrical phase suitable for the study of phase transitions in molecular simulations. |
Friday, March 19, 2021 10:36AM - 10:48AM On Demand |
X63.00014: Apex functionality dependent Frank-Kasper phases on dendron self-assembly Taesuk Jun, Hyunjun Park, Seungyun Jo, Hui Il Jeon, Hyungju ahn, Byeongdu Lee, Woo-Dong Jang, Du Yeol Ryu New complex sphere-packing of Frank-Kasper (FK) phases gradually emerge as the pioneering molecular platform to examine the assembly behaviors. For such purpose, we adopt a simple second-generation dendrons with a variety of apex functionalities to perform rich development of FK phases. Despite all the same dendritic wedges on body part of dendrons, the various sphere-packing phases are shown contributed from the different apex functionalities which attune the cohesive interactions. These sphere packing phases are measured and traced by in-situ small-angle X-ray scattering and FT-IR spectroscopy. The electron density maps of sphere-packing phases are reconstructed from X-ray scattering data to analyze each characteristic phase. The sphere particle sizes as well as isoperimetric quotient and coordination number are evaluated from electron density maps. To rationalize the free energy balance of dendron assemblies, we apply enthalpic/entropic effects which accommodate the cohesive energy of apex functionalities. Our approach to modulating the cohesive interactions in a basic second-generation dendron assembly envisions feasible strategy and primitive platform for manipulating diverse sphere-packing FK assemblies and quasiperiodic arrays. |
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