Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session E52: Thermodynamics and Physics of Polymer Films |
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Sponsoring Units: DPOLY Chair: Shudipto Dishari, Univ of Nebraska - Lincoln Room: LACC 512 |
Tuesday, March 6, 2018 8:00AM - 8:36AM |
E52.00001: Break - Polymer Physics Prize Talk
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Tuesday, March 6, 2018 8:36AM - 8:48AM |
E52.00002: Phase Transition Behavior of Block Copolymer Thin Films and Thickness Dependence YEONGSIK KIM, Sungmin Park, Hyungju Ahn, Du Yeol Ryu Understanding on the phase behaviors and transitions of Block copolymers (BCPs) such as order-to-disorder and order-to-order transitions plays a crucial role in designing a long-range order structure of self-assembled arrays. In this study, we investigated phase transition behavior of (BCPs) in film geometry, and compared with that of bulk system. When the BCP is confined in a film geometry, the interfacial interactions at air/polymer and polymer/substrates influence the phase transition temperatures of BCP and their effects on BCP films were more significant in thinner films. The morphologies and transition temperatures of BCP films were investigated by Grazing Incidence Small-Angle X-ray Scattering (GISAXS) measurements and Transmission Electron Microscopy (TEM). |
Tuesday, March 6, 2018 8:48AM - 9:00AM |
E52.00003: Perpendicular Orientation of PS-b-PMMA Microdomains Controlled by the Grafting Density of P(S-r-MMA) Brushes Wooseop Lee, Sungmin Park, Vaidyanathan Sethuraman, Nathan Rebello, Venkatraghavan Ganesan, Du Yeol Ryu Perpendicularly-oriented microdomains of diblock copolymer (di-BCP) was studied by means of fine-tuning the grafting density (σ) of random copolymer brushes, which balances the interfacial interactions between substrate and each block of BCP. In this study, a ‘grafting-to’ approach with end-functionalized random copolymer was applied to modify the silicon substrate and the thickness window for perpendicular orientation of lamella-forming di-BCP was observed in both ways of simulation and experiment. Moreover, we identified the minimal value of grafting density to achieve the largest thickness window, quantified by the radius of gyration of random copolymer chain (σRg2). The result provides a guide for the appropriate extent of surface modification by random copolymer, which leads to photolithography or nanoimprinting application of self-assembled BCP thin film. |
Tuesday, March 6, 2018 9:00AM - 9:12AM |
E52.00004: Shape Control of Uniform Block Copolymer Particles by Tuning Evaporation Rate of Emulsion Solvent Bumjoon Kim, Jae Man Shin, YongJoo Kim, Hongseok Yun, Gi-Ra Yi Shape and internal morphology of polymeric particles are of great importance for their unique physical properties. Block copolymer (BCP) self-assembly in evaporative emulsions can lead to non-spherical particle with unique nanostructure. Here, we report that evaporation rate of solvent (toluene) from uniform-sized emulsions containing symmetric polystyrene-b-polybutadiene (PS-b-PB) determines the shape and internal nanostructure of the BCP particles. A distinct morphological transition of the particles from ellipsoids with striped lamellae to onion-like spheres was observed as the evaporation rate was decreased, and the critical evaporation rate for the transition was dependent on the molecular weights of PS-b-PB. Furthermore, the evaporation rate was found to affect the self-assembly orientation of BCPs at the particle surface, which eventually determined the final structure of BCP particles. In the case of rapid evaporation, large differences between the toluene diffusivity in PS and in PB induced BCP to align perpendicular to the particle surface. By contrast, thermodynamic effects lead BCP to assemble parallel to the particle surface at slow evaporation. |
Tuesday, March 6, 2018 9:12AM - 9:24AM |
E52.00005: Non-Spherical Block Copolymer Particles: Mechanisms of Microstructure Orientation and Particle Elongation Jae Man Shin, YongJoo Kim, Kang Hee Ku, Gi-Ra Yi, Bumjoon Kim Shape-anisotropic block copolymer (BCP) particles received great attention. Previously, we reported generation of uniform polystyrene-b-polybutadiene (PS-b-PB) BCP ellipsoids by controlling evaporation rate of emulsion solvent (toluene). Here, we extend our study on ellipsoid formation mechanism in two aspects: 1) investigation of lamellae orienting mechanism on particle surface and 2) elongation behavior of ellipsoids. First, the perpendicular orientation of lamellae on ellipsoid results from solvent concentration gradient along the particle. As solvent evaporates, nucleation of BCP occurs at the surface followed by growth into the particle center. To describe this feature, propagation length of perpendicular lamellae (lper) was estimated using diffusion, partition and permeability coefficient of solvent. Experimentally, particles with length scale smaller than lper formed well-ordered ellipsoid, reflecting a valid prediction of lper. For the second case, we analyzed the aspect ratio of ellipsoid experimentally. Increase of aspect ratio was observed by increasing particle size and BCP molecular weight. This feature was captured by theoretical calculation of free energy for particle elongation that predicts the aspect ratio. |
Tuesday, March 6, 2018 9:24AM - 9:36AM |
E52.00006: Ionic Conduction through Block Copolymer Gyroidal Networks Moshe Dolejsi, Ban Dong, Paul Nealey As interest continues to grow into the effect of morphology on ion conduction, numerous efforts have been made to better characterize the unique structures found within block copolymer phase space. Of these phases, the gyroid phase possesses a unique triply periodic structure which allows for complete connectivity throughout real space. Furthermore the gyroid phase uniquely self orients both in lab and in nature to present the [110] plane. Here we demonstrate the use of a poly(isoprene-b-styrene-b-ethylene oxide) + carbonaceous additive system which allows for the creation of gyroid scaffolds with an active volume of over 80%. By shrinking the thickness to the thin film regime, we can fully analyze the morphology including grain boundaries to understand their effect on ionic conduction. Highly interdigitated electrodes are used to measure the conductivity in situ. |
Tuesday, March 6, 2018 9:36AM - 9:48AM |
E52.00007: Probing Coexisting Ordered Phases with X-ray Scattering Techniques in Block Copolymer Electrolytes Whitney Loo, Jacqueline Maslyn, Michael Galluzzo, Nitash Balsara Block copolymers have been studied for applications in lithium metal solid-state battery electrolytes due to their ability to microphase separate and decouple their ion conducting and mechanical properties. The addition of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt to poly(styrene)-block-poly(ethylene oxide) (SEO) has been shown to induce microphase separation and lead to the formation of ordered nanostructures. By tuning the composition, molecular weight, and salt concentration of the block copolymer electrolyte, complex morphologies such as coexisting ordered phases can be formed. Of particular interest is understanding the driving forces behind the formation of these phases as well as the salt distribution within the coexisting microphases. X-ray scattering techniques, such as small angle X-ray scattering (SAXS) and resonant soft X-ray scattering (RSoXS), were used to elucidate the nanostructures and salt distribution in these systems. This information can be used to predict block copolymer morphology in dynamic systems, such as those in an operating battery, where the introduction of salt concentration gradients can affect the polymer nanostructure across the cell. |
Tuesday, March 6, 2018 9:48AM - 10:00AM |
E52.00008: Morphological Transitions in Ionomer Thin Films Peter Dudenas, Adam Weber, Ahmet Kusoglu Perfluorosulfonic acid ion-conducting polymers (PFSA ionomers) are a key component to electrochemical catalyst layers, where they exist as nanometer-thick thin films. While it is known that these thin films deviate from their bulk morphology due to confinement and substrate interactions, the origin of such phenomena remains unknown. In this talk, a systematic investigation of different PFSA chemistries, thicknesses, and processing conditions is used to elucidate the driving forces for nanophase separation under confinement. Investigations include the effect of annealing temperature, as well as side-chain density and composition, on the film morphology using grazing incidence x-ray scattering (GIXS). The GIXS data is correlated to water uptake and swelling via simultaneous quartz-crystal microbalance (QCM) and ellipsometry to identify the impact of morphology on thermodynamic properties. |
Tuesday, March 6, 2018 10:00AM - 10:12AM |
E52.00009: Chain Confinement Entropy and Nanoconfined Polymerization Thermodynamics Qian Tian, Haoyu Zhao, Sindee Simon The equilibrium between monomer and polymer in free radical polymerization is shifted towards monomer under nanoconfinement, resulting in a decrease in the ceiling temperature. The magnitude of the shift is related to the confinement entropy, i.e., the entropy loss on confining a chain (ΔSchain). The confinement entropy scales with both the polymer chain length and the length scale of the nanoconfinent. Here, we report the results of an investigation of n-alkyl methacrylates confined to the pores of controlled pore glass using differential scanning calorimetry, with n ranging from methyl to ethyl to butyl to dodecyl. The confinement entropy is experimentally determined from the difference in the equilibrium conversion at a given reaction temperature between the bulk and nanoconfined cases. Confinement entropy decreases as the n-alkyl group increases from methyl to butyl, but there is an unexpected increase for dodecyl methacrylate. The scaling of confinement entropy with molecular weight and nanopore size will be discussed and compared to the literature. |
Tuesday, March 6, 2018 10:12AM - 10:24AM |
E52.00010: Suppression of Polymer Degradation in Polymer Infiltrated Nanoparticle Films Zahra Fakhraai, Haonan Wang, Jyo Lyn Hor, Daeyeon Lee In many industrial applications such as coatings and adhesives polymeric material are processed at high temperatures under conditions where most of the material is within a few nanometers from an interface, sometimes sandwiched between rigid surfaces. Under these conditions, reaction rates and pathways to degradation can be significantly affected, due to multiple factors. Variables such as the rate of oxygen diffusion into the film and product diffusion out, changes in polymer viscosity, interfacial interactions, and changes in the boundary condition from constant pressure to constant volume can affect the rate of degradation. In this study, we use capillary rise infiltration (CaRI) to infiltrated polystyrene in silica nanoparticles with various particle diameters. We show that as the particle diameter is decreased, polymer degradation can be significantly delayed, and the process may change from oxidative decay to pyrolytic degradation, despite heating in ambient conditions. We discuss the origins of this suppression of degradation and possible pathways to further improve polymer stability towards degradation. |
Tuesday, March 6, 2018 10:24AM - 10:36AM |
E52.00011: Solvent quality influences surface structure of glassy polymer thin films after
evaporation Antonia Statt, Michael Howard, Athanassios Panagiotopoulos In this talk, we present the structural effects of treating a glassy polymer thin film with solvents of varying quality and subsequently evaporating the solvent. Molecular dynamics simulations are used to investigate both a monodisperse and a polydisperse film for poor to good solvent conditions, including the limit in which the polymer film |
Tuesday, March 6, 2018 10:36AM - 10:48AM |
E52.00012: About (Dis)Entanglement and Knots in Confined Polymer Films. Hendrik Meyer The reptation mechanism introduced by de Gennes and Edwards, where a polymer diffuses along a fluffy tube defined by the constraints imposed by its surroundings, convincingly describes the relaxation of long polymers in concentrated solution and melts. We propose that the scale for the tube diameter is set by local chain segregation which we study analytically. We show that the concept of local segregation is especially operational for confined geometries, where segregation extends over mesoscopic domains drastically reducing binary contacts, and provide an estimate of the entanglement length, which increases with decreasing film thickness. Our predictions are quantitatively supported by extensive Molecular Dynamics simulations on systems consisting of long, entangled, chains [1]. A strong disentanglement is found for strong confinement. We now combine this finding with a recently proposed knot analysis [2] which shows an increase of self-entanglements in thin films. Their impact on dynamics, however, seems to be limited. |
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