Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session X52: Physics of Copolymers and Blends |
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Sponsoring Units: DPOLY Chair: Tirtha Chatterjee, Dow Chemical Co Room: LACC 512 |
Friday, March 9, 2018 8:00AM - 8:12AM |
X52.00001: Field-theoretic Monte Carlo simulation of the suppression of the order-disorder temperature in a fluctuating asymmetric diblock copolymer melt Jeffrey Roberts, Robert Wickham We use Monte Carlo simulation to sample density field configurations weighted by a Landau-Brazovskii effective Hamiltonian and systematically investigate the fluctuation-induced suppression of the order-disorder temperature (ODT) in an asymmetric diblock copolymer melt as we decrease the invariant degree of polymerization from 106 to 103. Derivatives of the thermodynamic free energy correspond to Monte Carlo averages, and we use thermodynamic integration to compute the free energy itself. We compare the ordered BCC sphere phase free energy to that of the disordered phase to locate the ODT. Turning on a BCC-ordering field enables us to bypass the discontinuity at the ODT and to integrate continuously from order to disorder. We find that the BCC free energy is relatively insensitive to fluctuations. However, in the low-temperature regime of disorder, fluctuations stabilize a disordered liquid of micelles, which we characterize. To accurately locate the ODT, we take care to ensure that the disordered micelles are equilibrated. |
Friday, March 9, 2018 8:12AM - 8:24AM |
X52.00002: Effect of polydispersity on the dynamics, structure, and topology of entangled lamellae forming block copolymers Brandon Peters, Gary Grest While essentially all previous simulations of diblock copolymers have studied uniform chain lengths, experimentally, the polymer synthesis always result in a distribution of molecular weights. Here we present molecular dynamics simulations comparing the structure and dynamics of uniform diblock copolymers with those with dispersity in the chain length of one or both blocks. We vary the dispersity in molecular weight near that available experimentally, Mw/Mn = 1.02-1.08. As the dispersity increases, the interfacial width broadens and the average diffusion of the chains parallel to the increases as the increased mobility of the short chains outweighs the decrease in the long chains. A primitive path analysis is used to identify the spatial distribution of entanglements. As the chemical incompatibility between the blocks decreases towards the order disorder transition, the interfacial width is further increased and the spatial distribution of the entanglements changes. |
Friday, March 9, 2018 8:24AM - 8:36AM |
X52.00003: Triply Periodic Bicontinuous Network Structures of Various Symmetries for Molten Block Copolymers Junhan Cho The evolution of new triply periodic bicontinuous morphologies of molten diblock and triblock copolymers is theoretically studied in a mean-field level. The evolved mesophases are probed through characteristic peaks in the scattering functions and the real-space visualization. The ABC or AB copolymers at selected compositions and segregation levels exhibit holey network structures, where the channels are wholly connected with tetrapod units. There also evolves a network resembling one type of zeolites. The curvatures, surface areas, and genera g of their dividing surfaces are estimated by matching them to proper model surfaces. The obtained surface properties of the newly developed networks are discussed in comparison with those of the known bicontinuous networks such as double gyroids and double diamonds. In addition, we discuss how to analyze the effects of charges at the terminal groups on mesophase evolution. |
Friday, March 9, 2018 8:36AM - 8:48AM |
X52.00004: The Influence of One Block vs. Two Block Polydispersity on Phase Separation of Diblock Copolymers Inho Kim, Yeonji Choe, Sheng Li Polymer composition (f) and segregation strength (χN) are two key parameters that determine the microphase separation behavior of block copolymer. However, recent findings show that block polydispersity can also influence block copolymer phase separation. The published studies thus far have been mainly focused on the phase behavior of asymmetric systems where at least one of the blocks is monodisperse. With the recent advances in polymer synthesis, living free radical polymerization condition can be modified to achieve block copolymer with controlled polydispersity. We prepared a series of poly(styrene)-b-poly(methyl methacrylate) diblock copolymers where either one block is polydisperse or both blocks are polydisperse. The phase separation and microdomain morphology of these diblocks were then examined and compared to illustrate the importance of controlling polydispersity on block copolymer phase behavior. |
Friday, March 9, 2018 8:48AM - 9:00AM |
X52.00005: Intradomain Phase Transitions in Block Copolymers with Intradomain Ordering Christopher Burke, Gregory Grason Block copolymers (BCPs) form a variety of microphase separated structures depending on e.g. monomer fractions, monomer immiscibilities, and chain topology. Here we turn our attention to the effect of orientational interactions among chain segments in the limit of flexible chains. Even in the absence of orientational interactions, flexible BCPs exhibit orientational order of chain segments which is coupled to their mesophase domain structure. Due to the intrinsic alignment generated by micro-domain formation alone, even a weak enthalpic preference for local segment alignment has strong non-linear effects on the pattern of segment alignment at the sub-domain scale. We show here that by increasing the enthalpy of alignment, lamellar BCP phases undergo a new type of SmA-SmC transition in which lamellar sub-domains exhibit a spontaneous tilt relative to the lamellar layers. This transition from normal to in-plane tilt patterns takes place within a single lamellar domain due to the intrinsic spatial variations of segment alignment favored by chain connectivity. We also explore the influence of Frank elastic penalties for sub-domain orientational gradients and their tendency to suppress in-plane ordering associated with the SmC phase. |
Friday, March 9, 2018 9:00AM - 9:12AM |
X52.00006: Magnetic Field Alignment of Coil-Coil Block Copolymers and Blends via Intrinsic Chain Anisotropy Yekaterina Rokhlenko, Apostolos Avgeropoulos, Edwin Chan, Chinedum Osuji Magnetic field alignment of block copolymers has typically relied on the presence of liquid crystalline (LC) or crystalline assemblies to provide sufficient magnetic anisotropy to drive alignment. Here we describe the field response of a wide variety of non-LC systems under magnetic fields, including coil-coil block copolymers like PS-b-P4VP, PS-b-PDMS, and PS-b-PMMA, blends of block copolymers of disparate morphologies and molecular weights, blends of block copolymers with homopolymers, and bottlebrush copolymers. Blends of PS-b-P4VP with poly(ethylene glycol) (PEG) provide a route to form size-selective nanoporous materials with aligned channels by preferential dissolution of PEG. PS-b-PMMA demonstrates an unusual field response which appears to be governed by anisotropic growth of grains coupled with confinement effects. We survey these various systems using in-situ X-ray scattering and transmission electron microscopy to study the phase behavior and temperature-, time- and field-dependent dynamics of alignment, highlighting fundamental insights and opportunities for novel applications. |
Friday, March 9, 2018 9:12AM - 9:24AM |
X52.00007: Effects of Polydispersity on the Stability of Complex Spherical Packing Phases in Diblock Copolymers Chi To Lai, Weihua Li, Anchang Shi The effects of polydispersity on the relative stability of complex spherical packing phases, i.e., the Frank-Kasper phases, self-assembled from conformationally asymmetric AB diblock copolymers are studied using the self-consistent field theory (SCFT). Previous experimental and theoretical studies have revealed that the Frank-Kasper σ-phase could be stabilized by the conformational asymmetry between the A- and B-blocks. The current SCFT results reveal that polydispersity in the minority A-blocks could enhance the stability of the complex spherical packing phases, resulting in a wider stable region of the Frank-Kasper σ-phase in the phase diagram. Furthermore, the effects of polydispersity on the formation of the Frank-Kasper σ-phase depend on the chain length distribution of the polymers. Different chain length distributions with a given polydispersity index could have very different effects on the stability region of the Frank-Kasper σ-phase. The mechanisms of stabilizing the complex spherical packing phases are analyzed by examining the chain-length driven local segregation of the block copolymers. |
Friday, March 9, 2018 9:24AM - 9:36AM |
X52.00008: A Direct Approach to Giant Gyroid Structures from Block Copolymer Self-Assembly Sungmin Park, Pil Yoo, Su-Mi Hur, Du Yeol Ryu A gyroid structure obtained from block copolymer (BCP) self-assembly is regarded as a unique complex structure, and its structural character promises a prospective route to produce uniform arrays adjustable in periodicity depending on its molecular weight. In this study, we investigate a feasible approach to the direct development of gyroid nanostructure in high-molecular-weight, composition-controlled polystyrene-b-poly (methyl methacrylate) (PS-b-PMMA) films. The use of a neutral solvent vapor to elaborately control the swelling of BCP films is essential to generate a direct pathway to gyroid structure through a hexagonal cylindrical morphology in the same material. Moreover, the influence of interfacial interactions from substrate to final morphology was explored. In the final formation of film structures, we identified the two different gyroid planes on the surface throughout the interior of the films. |
Friday, March 9, 2018 9:36AM - 9:48AM |
X52.00009: Phase Behavior of Block Copolymer Brushes: Consequence of Grafting Density Control GaRyang Kang, Dongwan Son, Myungwoong Kim, Juan De Pablo, Su-Mi Hur Block copolymer (BCP) brushes, surface-anchored BCP chains, form nano-scaled structures in similar fashion to self-assemblies in BCP films. Resulting structures can be utilized to control surface properties in various nanotechnologies, thus a comprehensive understanding on the phase behavior is crucial. Previous studies predicting morphologies in BCP brushes were focused on the role of block composition, segregation strength between the blocks, and solvents while the grafting density was fixed at relatively high value. However, the morphologies and properties of polymer brushes are strongly governed by the grafting density; hence, we aim to understand how grafting density affects the self-assembly in BCP brushes. Using a coarse-grained simulation model of polymer brush, we investigate the self-assembly of BCP brushes with the variation of system conditions to complete a phase diagram which encompasses a wide range of parameter space. We also compare our simulation results with experimental data where grafting density is effectively controlled using a new synthetic method. |
Friday, March 9, 2018 9:48AM - 10:00AM |
X52.00010: Self-Assembly of Computationally Designed Amphiphilic Block copolymers in Solution Jee Young Lee, Arthi Jayaraman, Karen Wooley, Darrin Pochan Computationally designed amphiphilic poly(d-glucose carbonate),PGC, block copolymers (BCP) with targeted block compositions and chain lengths are assembled into various nanostructures as determined by the simulation studies. Based upon previous studies on kinetically trapped BCP structures, we first explore the bulk solution assembly behavior of PGCs using a range of solvent mixtures. Then we further tailor the kinetic pathway by introducing a simulation-guided parameter such as interfaces. We take advantage of the dynamic interaction changes between the polymer nanoparticles and the surface in response to a changed solution environment i.e. solvent quality or pH to induce the subsequent chain rearrangement of the adsorbed polymer nanoparticles. These assembled nanostructures with morphologies that are highly dependent on the surface and polymer chemistry, and solution environment, allow us to explore a variety of novel structures. We control the assembly parameters by adjusting solvent compositions and conditions with time as well as by using surface-treated silicon wafer or mica as a substrate. Both cryogenic-TEM and liquid AFM are used to monitor the assembled structure formation in-situ. |
Friday, March 9, 2018 10:00AM - 10:12AM |
X52.00011: Polymer mediated interactions between spherical fillers immersed in polymer blend. Alexander Chervanyov
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Friday, March 9, 2018 10:12AM - 10:24AM |
X52.00012: Study for Coordination Power between Poly(2-vinylpyridine) and Poly(4-vinylpyridine) by Phase Behavior of Poly(2-vinyl pyridine)-block-poly(4-vinyl pyridine) copolymer with Gold Nanoparticles. Jaeyong Lee, Jongheon Kwak, Chungryong Choi, Jin Kon Kim For study the coordination power for metal precursor between Poly(2-vinylpyridine) and Poly(4-vinylpyridine), We studied, for the first time, the phase behavior of poly(2-vinyl pyridine)-block-poly(4-vinyl pyridine) copolymer (P24VP) with gold nanoparticles via rheometry, small angle X-ray scattering (SAXS), differential scanning calorimetry (DSC), TEM and S-TEM. Although both blocks of P24VP exhibit attractive interaction to gold nanoparticles, we found it shows the unusual phase behavior as increasing the amount of gold nanoparticles. Neat P24VPs with lamellar or cylinder microdomains show fully ordered phases over the entire experimental temperatures up to 300oC. |
Friday, March 9, 2018 10:24AM - 10:36AM |
X52.00013: Fluctuation effects in A + B + AB ternary polymer blends Russell Spencer, Mark Matsen Adding copolymers to homopolymer blends enhances their compatibility and, at higher copolymer concentrations, leads to the formation of microemulsions. Contrary to what is seen in mean-field theory, experiments find that the disordered phase invades the ordered region of the phase diagram, introducing a channel of microemulsions. The channel separates the two-phase region, on the homopoylmer-rich side, from the lamellar region, on the copolymer-rich side. This modification to the phase behavior is due to fluctuations, and understanding it requires simulations that go beyond mean-field theory. We build on existing simulation techniques, extending Monte Carlo field-theoretic simulations of ternary blends into three dimensions, and introducing new semi-grand canonical ensembles, in order to tackle the problems of phase behavior, interfacial properties and the nature of microemulsions. This work examines A and B homopolymers with the experimentally relevant invariant polymerization index of Ñ = 104, blended with symmetric AB diblock copolymers of lengths α=2.5, 5 and 10 times longer than the homopolymers. |
Friday, March 9, 2018 10:36AM - 10:48AM |
X52.00014: Mechanical and antithrombogenic properties of 2-methoxyethyl acrylate and methyl methacrylate triblock copolymers Naruki Kurokawa, Fuyuaki Endo, Kenta Bito, Tomoki Maeda, Atsushi Hotta Poly(2-methoxyethyl acrylate) (PMEA) is a promising material that can be used for biomedical devices due to its excellent antithrombogenicity, inhibiting the adhesion of platelets. PMEA is, however, a liquid-like polymer which cannot be used as a solid material. Thus triblock copolymerization with a rigid polymer could be an effective way to solidify the liquid-like PMEA. In this study, we synthesized methyl methacrylate (MMA)-b-2-methoxyethyl acrylate (MEA)-b-MMA triblock copolymers with different volume fractions of the MMA blocks (fMMA). We investigated the mechanical properties and the antithrombogenicity. The molecular weight of the triblock copolymers were analyzed by NMR. It was confirmed that the fMMA could be successfully controlled and the mechanical properties of the triblock copolymers could change from rigid to elastic by varying the fMMA. The triblock copolymers with the fMMA below 0.4 presented an excellent antithrombogenicity similar to that of PMEA homopolymer. The triblock copolymer could be a great candidate as a new material for biomedical applications such as vascular grafts. |
Friday, March 9, 2018 10:48AM - 11:00AM |
X52.00015: Improved Ordering in Low Molecular Weight Protein-Polymer Conjugates Through Oligomerization of the Protein Block Justin Paloni, Bradley Olsen Due to the enhanced stability of small affinity binders such as nanobodies and engineered binding proteins, there is a growing desire to incorporate these materials into biosensors. Performance in these biosensors is strongly linked to protein density and accessibility of binding sites. While our group has previously demonstrated the ability to create arrays of densely-packed, well-oriented proteins by conjugating these proteins to polymers, the ordering with low molecular weight protein blocks is poor. Here, we demonstrate that oligomerization of small proteins significantly improves ordering in protein-polymer conjugates due to an increase in the overall molar mass of the conjugate. A series of four oligomers—monomer to tetramer—of a small binding protein are synthesized by connecting proteins via a short, flexible peptide linker. Small-angle X-ray scattering (SAXS) measurements reveal that while conjugates of the monomer exclusively exist in disordered states, oligomer conjugates self-assemble into long-range ordered lamellae. As the protein degree of oligomerization is increased, the concentration range over which strong ordering is observed is broadened. Binding assays indicate that activity is retained with oligomerization. |
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