Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session G16: Polymers and Block Copolymers at Interfaces IIFocus Recordings Available
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Sponsoring Units: DPOLY DSOFT Chair: Zhe Qiang, University of Southern Mississippi Room: McCormick Place W-184A |
Tuesday, March 15, 2022 11:30AM - 12:06PM |
G16.00001: Biopolymer self-assembly and aggregation at interfaces Invited Speaker: Zahra Fakhraai Amyloid fibrils, typically form through a nucleation and growth mechanism, in a process analogous to polymer crystallization. The nucleation step typically requires a minimum concentration of peptides in the solution, thus preventing this one-dimensional crystallization process from moving forward in dilute solutions. However, under the right conditions, surfaces can promote rapid self-assembly of mono-layer thick amyloid fibrils within minutes. We demonstrate that this surface-enabled self-assembly process can proceed through diffusion-limited aggregation, without a nucleation barrier. On a rigid hydrophobic surface, the adsorbed peptides minimally disrupt the water structure and can as such rapidly diffuse, while roughness and softness can disrupt this process. The deposition rate of the peptides, as well as their orientation and diffusion on the surface, are also important factors in aggregation, which strongly depend on the effective surface energy. The self-assembly can be suppressed either by reducing the interaction such that the deposition rate is reduced or by increasing the interaction energy to a point where the peptide diffusion is substantially reduced. However, the absorption of amphiphilic peptides themselves can disrupt this process, by changing the effective surface energy. Depending on the nature of the side chains, the surface can become more hydrophobic or hydrophilic and promote or prevent the further deposition of the peptides. We develop a new method to measure the dynamic change in the surface energy and its effect on the kinetics of adsorption/desorption and surface-mediated aggregation. We demonstrate how under the right conditions, the peptide absorption can be self-limiting, allowing control over two-dimensional self-assembly and the final effective surface energy. This process can be envisioned as a method for the directed assembly of amphiphilic polymers and biopolymers. |
Tuesday, March 15, 2022 12:06PM - 12:18PM |
G16.00002: Lipid Layer Formation on Particle Surfaces by Using DNA-Containing Recruiter Molecules Sheng Li, Jeehae Shin Biofunctional interfaces containing DNA-conjugated molecules have been explored for various bioengineering applications. In this study, we prepare DNA-containing recruiter molecules and incorporate them onto DNA immobilized gold nanoparticles through DNA hybridization. Liposomes composed of different phospholipids are then applied to investigate supported lipid layer formation on these recruiter-containing surfaces. We find that the morphology and the amount of lipid layers formed are determined by both the liposome concentration and the type of recruiter molecule. When liposomes are applied in excess above a critical concentration, surface chemistry determines the lipid layers formed, leading to lipid multilayers on hydrophilic DNA recruiter containing surface and lipid monolayers on hydrophobic DNA-lipid recruiter containing surfaces. When the liposome concentration is below the critical value, then surface chemistry is overtaken by recruiter-lipid interactions, leading to the active lipid recruitment on particle surfaces. The total amount of the lipid layers formed is further modulated by the overall charge and the fluidity of the liposomes applied. |
Tuesday, March 15, 2022 12:18PM - 12:30PM |
G16.00003: Mechanical properties of glassy polymer nanocomposites via atomistic and continuum models: The role of Interphases Vagelis Harmandaris, Hilal Reda, Nikos Savva, Alireza Foorazani Behbahani, Anthony Chazirakis We propose a novel hierarchical computational approach to predict the distribution of mechanical properties of polymer nanocomposites (PNCs), based on homogenization approaches and atomistic molecular dynamics (MD) simulations. The homogenization methodology follows a systematic nano/micro/macro coupling between detailed atomistic non-equilibrium MD simulations and a variational approach based on the Hill–Mandel lemma. We apply the proposed scheme in model glassy polybutadiene/silica PNCs for different nanoparticle (NP) volume fractions. Using MD simulations, we directly probe the polymer/NP interphases under non-equilibrium conditions (tensile deformation), and compute the density, stress and strain distributions. A detailed analysis reveal the role of different chain conformations (train, loops, bridges) to the mechanical properties at the interphase. The effective Young modulus and Poisson ratio of the organic/inorganic interphases are directly calculated from the local stress and strain data. Interphases are shown to exhibit higher rigidity compared to the bulk material. The distribution of mechanical properties across the atomistic model PNCs is used together with the homogenization approach to develop a continuum model for predicting the mechanical properties of the PNCs. |
Tuesday, March 15, 2022 12:30PM - 12:42PM |
G16.00004: Stractural and Dynamical Properties of Hybrid Polymer/Gold and Core-Shell Nanoparticle Systems through Molecular Dynamics Simulations Albert J Power, Ioannis N Remediakis, Vagelis Harmandaris We present a detailed investigation of polymer nanocomposites (PNCs) with a bare and functionalized nanoparticle (NP) via detailed atomistic molecular dynamics (MD) simulations. Our model systems consist of polyethylene (PE) matrix with dispersed bare or functionalized gold (Au) NPs. We probe the structural and dynamical properties of polymer chains in the PNCs focusing on the PE/Au interphase. An oligomeric PE matrix with 22 monomers per chain and a Rouse-like one with 100 monomers per chain are examined. Also different model gold NPs, using the Wulff construction, with a diameter from 2.5 nm up to 5.0 nm, are considered. The grafting density for the core-shell NP systems is 0.67 chains/nm2. We examined properties of the PE chains as a function of the distance from the Au NP. That allow us to examine the way spatial and dynamical heterogeneities are related to the molecular structure, in particular at the vicinity of the PE/Au interphase. Results concerning polymer density profiles, bond order parameter, segmental and terminal dynamics show that the size of the interface/interphase, depends on the actual property under study. In addition, the anchored polymeric chains change the behavior/properties of the polymer chains, and especially the chain density profile and the dynamics, at the vicinity of the Au NP. |
Tuesday, March 15, 2022 12:42PM - 12:54PM |
G16.00005: Entropic Surface Segregation from Athermal Polymer Blends due to Conformational Asymmetry Russell K Spencer, Mark W Matsen Surface segregation of polymers based on conformational asymmetry is a subtle effect, and the literature is divided regarding questions as basic as whether the stiffer or more flexible polymer segregates to the surface. This work uses Monte Carlo simulations to investigate the surfaces of athermal blends of stiff and flexible polymers as the bending modulus of the stiff polymers, κ, is increased from zero to the point where the bulk undergoes an isotropic−nematic transition. For hard walls characteristic of polymer/solid surfaces, the flexible polymers segregate to the surface and follow the universal concentration profile predicted by mean-field theory [Wu et al., J. Chem. Phys. 1996, 104, 6387]. This prediction breaks down for higher κ, where packing becomes important and a thin nematic layer rich in stiff polymers forms next to the wall. This appears to be followed by a second surface transition where the degree of order abruptly increases, which, in turn, causes a rapid thickening of the nematic layer that nucleates the bulk nematic phase. |
Tuesday, March 15, 2022 12:54PM - 1:06PM |
G16.00006: Empirical Scaling Relations for Block Copolymer Surface Micelles Dong Hyup Kim, So Youn Kim Block copolymers (BCPs) form surface micelles at the air/water interface and change the structures with varying surface pressures. BCP surface micelles have the structure of core and corona similar to the conventional BCP micelles in solutions but their chain conformations are different because a micellization occurs two-dimensionally at the air/water interface. Thus, the structure of BCP surface micelles cannot be described with conventional scaling relations established for BCP micelles in solutions. Despite three decades of research progress since the first observation of BCP surface micelles, even the most fundamental principle of BCP surface micelles, such as scaling relations, is still in a veil. Here, we report empirical scaling relations of BCP surface micelles based on an extensive set of data collected from both scattering-based analysis and microscope-based analysis. We firstly found the intrinsic scaling relations in a surface pressure-free environment and then investigated the extrinsically changed scaling relations depending on the surface pressure, and finally unified the scaling relations regardless of the types of BCPs by introducing the concepts of excluded volume-dependent scaling exponent. |
Tuesday, March 15, 2022 1:06PM - 1:18PM |
G16.00007: Morphology Transition of Block Copolymer Surface Micelles by Solvent Immersion Seokyoung Bae, Dong Hyup Kim, So Youn Kim While amphiphilic block copolymers (BCPs) form micelles in a selective solvent, they form surface micelles at the air-water interface in a similar manner but different chain conformation. Unlike BCP micelles in solution, the structure of surface micelles can be effectively varied by changing surface pressure. |
Tuesday, March 15, 2022 1:18PM - 1:30PM |
G16.00008: Molecular Weight-Dependent Self-Assembly Behavior of Bottlebrush Block Copolymer in Emulsion Droplet Eun Ji Kim, Jaeman J Shin, Taeyang Do, Gue Seon Lee, Juhae Park, Vikarm Thapar, Jinwoong Choi, Joona Bang, Gi-Ra Yi, Su-Mi Hur, Jeung Gon Kim, Bumjoon J Kim The molecular weights and chain-rigidities of block copolymers can strongly influence their self-assembly behavior, particularly when the block copolymers are under confinement. We investigate the self-assembly of bottlebrush block copolymers (BBCPs) under emulsion driplet, where each block consisted of polystyrene (PS) and polylactide (PLA). The molecular weight of BBCP was found to be critical in the distinct morphological transition of the particles from onions to ellipsoids. This is rationalized by the competition between the particle surface/surroundings interactions and the chain stretching/bending penalty of the BBCPs. The coarse-grained simulations of BBCP emulsion droplets by an implicit solvent model also supported the morphological transition with the analysis of the favored chain alignment at the free surface. Finally, the shape-anisotropy (in terms of aspect ratio (AR)) of the BBCP ellipsoids was performed to investigate the origin of the large value of the AR. |
Tuesday, March 15, 2022 1:30PM - 1:42PM |
G16.00009: Order-to-disorder Transition of Block Copolymers with Discrete Chain Model and Finite-range Interaction Jaeup Kim, Daeseong Yong, Wonjun Kang Enormous experimental and theoretical studies have been conducted on the order-to-disorder transition (ODT) of block copolymers (BCPs). Thanks to the earlier random phase approximation (RPA) and self-consistent field theory (SCFT) calculations, it is now well known that the ODT point of symmetric AB BCP melt is (χN)ODT = 10.495 in the mean field limit, when standard Gaussian chain model is adopted. However, the story becomes more complicated for short polymer chains for which Gaussian chain model is not appropriate and finite-range interaction is naturally present in the model, even before considering the compositional fluctuation effect. In this talk, we first present RPA calculation result of discrete chain model with finite-range interaction and show that the ODT change strongly depends on the chain model. In a series of publications on ODT change of thin BCP films, we utilized SCFT calculation with finite-range interaction to confirm the experimentally observed ODT change when the interfaces are preferential and/or neutral. We also performed Langevin field-theoretic simulation boosted by deep learning technique in an effort to identify the effect of compositional fluctuation at experimentally relevant low invariant polymerization index regime. |
Tuesday, March 15, 2022 1:42PM - 1:54PM |
G16.00010: Symmetry-Breaking of Double Gyroid structures in Block Copolymer Films by Non-affine Distortion Seungyun Jo, Haedong Park, Taesuk Jun, Byeongdu Lee, Seungwoo Lee, Du Yeol Ryu In this study, we suggest that a solvent vapor annealing, which forms self-assembled gyroid structures in polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) films, causes unique structural distortion owing to unidirectional deformation upon deswelling processes. The rapid and spontaneous deswelling of the swollen PS-b-PMMA films immediately upon solvent vapor annealing lead to triclinic gyroid structures with different z-directional contraction ratios, maintaining the lateral dimensions. Our grazing-incidence X-ray scattering (GISAXS) analyses reveal several forbidden reflections such as {110} and {200} reflections that indicate a non-affine distortion generated during the deswelling process, where forbidden reflections for more contracted gyroid film are stronger than those for less contracted one. To closely observe the lattice distortion, we compute electron-density difference maps extracted from GISAXS patterns. Furthermore, a level-set approach, which is utilized to quantitate the structural characteristics of the two alternating PMMA channels, elucidate the inversion symmetry-breaking of gyroid structures, which enable us to exploit its possible application to optical Weyl photonic crystals. |
Tuesday, March 15, 2022 1:54PM - 2:06PM |
G16.00011: Diverse Frank-Kasper phases in High-χ and Conformationally Asymmetric PDMS-b-PTFEA Copolymers Seungbae Jeon, Taesuk Jun, Sangwoo Lee, Byeongdu Lee, Du Yeol Ryu The Frank-Kasper (FK) phases which were originally observed in metal alloys have emerged with single-component block copolymers (BCPs) self-assembly providing a new potential in soft matters since the early 2000s. To directly impact these low-symmetry structures, here, we introduce a new-type of BCPs with high-χ and high-ε, where χ and ε are the Flory−Huggins interaction parameter and conformational asymmetry between the two blocks, respectively. The compositional asymmetric Polydimethylsiloxane-b-poly(2,2,2-triflouroethyl acrylate) (PDMS-b-PTFEA) copolymers were precisely synthesized via atom transfer radical polymerization using the same PDMS block. As a result, using small-angle X-ray scattering, we systematically explore the self-assembled packing structures of PDMS-b-PTFEAs in the space of temperature versus the volume fraction of core-forming PTFEA blocks (fPTFEA). As fPTFEA decreases, the sphere-packing phase behavior exhibits the composition dependence of the FK phases (A15, σ, and C14) and classical body-centered cubic (BCC) phase. The experimental sequence of sphere-packing phases agrees with the free-energy density calculation of A15−σ−C14−BCC with decreasing fPTFEA, which are subject to both high-χ and high-ε nature of PDMS-b-PTFEAs. |
Tuesday, March 15, 2022 2:06PM - 2:18PM |
G16.00012: Multidomain Helical Nanostructure by A1BA2C Tetrablock Terpolymer Self-Assembly JinKon Kim, Hyeongkeon Yoon Among many possible nanostructures in block copolymer self-assembly, helical nanostructures are particularly important because of potential applications for heterogeneous catalysts and plasmonic materials. In this work, we investigated, via small-angle X-ray scattering and transmission electron microscopy, the morphology of a polystyrene-block-polyisoprene-block-polystyrene-block-poly(2-vinylpyridine) (S1IS2V) tetrablock terpolymer. Very interestingly, when the volume fraction of each block was 0.685, 0.125, 0.060, and 0.130, respectively, a multidomain double-stranded helical nanostructure (MH2) was formed: P2VP chains became a core helix, and PI chains formed double-stranded helices surrounding the core helix. Core and double-stranded helices are connected by short PS2 chains, and PS1 chains become the matrix. The experimentally observed morphology is in good agreement with the prediction by self-consistent field theory. We believe that this multidomain helical structure will be pave the way to the creation of multifunctional helical structures for various applications such as metamaterials. |
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