Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session Y19: Polymer Blends |
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Sponsoring Units: DPOLY Chair: Hengxi Yang, University of Michigan Room: 404 |
Friday, March 7, 2014 8:00AM - 8:12AM |
Y19.00001: What Drives Blend Miscibility? Ronald White, Jane Lipson With no mixture data available, can one predict phase behavior in polymeric systems based on pure component information only? Due to the very weak entropic drive for large molecules to mix, predicting and understanding miscibility behavior is indeed very difficult. However, while not perfect, some \textit{a priori} insight is attainable when pure component properties are analyzed within the framework of a theoretical model. A theory provides a platform, allowing one to define quantities and other measures that may not always be directly measurable, but, are physically appealing and insightful none-the-less. Are there properties that can explain for example, why a polymer like polyisobutylene (PIB) exhibits such different phase behavior compared to other polyolefins? Applying our simple lattice-based equation of state, we have recently analyzed a large number of different polymers. In this talk we will present insights from trends and patterns we have observed. [Preview Abstract] |
Friday, March 7, 2014 8:12AM - 8:24AM |
Y19.00002: Miscibility of Polymers in Supercritical Carbon Dioxide Jeffrey DeFelice, Jane Lipson We have developed a simple model that allows us to correlate underlying thermodynamic behavior with trends in miscibility, which we have applied to mixtures of polymers and supercritical carbon dioxide (scCO$_{2})$. scCO$_{2}$ is considered a ``green'' solvent, making it an attractive choice over familiar organic solvents. Experimental cloud point investigations have determined the miscibility of a diverse array of polymers in scCO$_{2}$. Properties of these polymers such as fluorination, alkyl group size, and molecular weight have a strong effect on mixture miscibility. Although polymer/scCO$_{2}$ mixtures have been modeled with some success in the past, the ability of an equation of state (EOS) to make accurate predictions has yet to be demonstrated. We have used a simple EOS to study several of these mixtures. We draw insight from the trends observed via our parameterization of pure component experimental data and discuss how the use of pure component information, alone, leads us to predictions about mixture behavior. This will ultimately aid in our understanding of what is controlling polymer miscibility in scCO$_{2}$. [Preview Abstract] |
Friday, March 7, 2014 8:24AM - 8:36AM |
Y19.00003: Effect of supercritical carbon dioxide on the thermodynamics of miscible polymer blends Nicholas Young, Sebnem Inceoglu, Andrew Jackson, St\'ephane Costeux, Nitash Balsara The design of environmentally-benign polymer processing techniques is an area of growing interest, motivated by the desire to reduce the emission of volatile organic compounds. Recently, supercritical carbon dioxide (scCO$_{2})$ has gained traction as a viable candidate for various processes as either a polymer solvent or diluent. To elucidate the impact of scCO$_{2}$ on polymer miscibility, the phase behavior and thermodynamic interactions of multicomponent mixtures comprising scCO$_{2}$, styrene-acrylonitrile copolymer (SAN), and poly(methyl methacrylate) (PMMA) were studied by small angle neutron scattering. Application of the Random Phase Approximation and Flory-Huggins Theory allowed quantitative analysis of scattering profiles to obtain the dependence of pairwise interaction parameters on scCO$_{2}$ activity. The location of the spinodal boundary was found to have a non-trivial dependence on scCO$_{2}$ processing conditions which can be interpreted in the context of balancing interaction strengths. The presence of scCO$_{2}$ was shown to disrupt the miscibility of SAN-PMMA induced by intramolecular repulsion, and decrease the accessible demixing temperature by over 130 $^{\circ}$C. [Preview Abstract] |
Friday, March 7, 2014 8:36AM - 8:48AM |
Y19.00004: Composition Dependency of the Flory-Huggins $\chi $ Parameter in Isotopic Polymer Blends Travis Russell, Brian Edwards, Bamin Khomami Flory-Huggins Theory has been the basis for understanding polymer solvent and blended polymer thermodynamics for much of the last 50 years. Within this theory, a parameter ($\chi$) was developed to account for the energy of dispersion between distinct components. Thin film self-assembly of block copolymers and polymer melts depends critically on this parameter, and in application, $\chi$ has generally been assumed to be independent of the concentrations of individual components in the system. However, Small Angle Neutron Scattering data on isotopic polymer blends, such as polyethylene and deuterated polyethylene, have shown a parabolic concentration dependency for $\chi$. In order to better understand the nature of $\chi$ and develop more accurate morphological data for polymer systems, an investigation of this concentration dependency was undertaken from both structural ($\chi$S) and thermodynamic ($\chi$T) theories. Structural calculations for $\chi$S were based on the Random Phase Approximation of de Gennes, and thermodynamic information was obtained through integration of the free energy with $\chi$T defined using original Flory-Huggins Theory. Comparison of the two theories revealed that while both $\chi$S and $\chi$T possess a composition dependence, it is not the same. [Preview Abstract] |
Friday, March 7, 2014 8:48AM - 9:00AM |
Y19.00005: Controlling Morphology in Coatings Made from Polyolefin Dispersions Jodi Mecca, Jeffrey Wilbur, Rick Lundgard, Sean Tang, Bernhard Kainz Semi-crystalline polymers have excellent mechanical properties, thermal stability, and chemical resistance that would be attractive for coating applications, but those same properties make it impractical to efficiently deposit these materials using solvent-based or 100{\%} solid approaches. Instead, aqueous formulations have been developed based on polyolefins dispersed as micron-scale particles. The macroscopic properties of coatings made from these materials are strongly dependent on coating morphology, which in turn is governed by the interactions between component polymers, the curing chemistry and the curing process. We will discuss thermodynamic and kinetic approaches to control the morphology and macroscopic properties of coatings based on polyolefins. [Preview Abstract] |
Friday, March 7, 2014 9:00AM - 9:12AM |
Y19.00006: Tuning the Miscibility of Polystyrene / Poly(vinyl methyl ether) Blends with Electric Fields Annika Kriisa, Connie Roth Application of electric fields seem experimentally simple, as they can be switched on and off instantly and effortlessly. Nevertheless the influence of electric fields on the phase separation temperature Ts in small molecules and polymeric mixtures is not yet well understood. Available theoretical calculations use thermodynamic arguments for adding an electrostatic free energy term to the total free energy of mixing and predict changes in Ts due to external electric fields that are much smaller than what most experimental results report. To date, neither theory or experiments have found a clear consensus on whether uniform electric fields enhance mixing or demixing. As only a few experimental results have been published over the past several decades with typically only small shifts in Ts, more experiments with unambiguously large shifts in Ts are needed to better understand this effect. Using a fluorescence technique we have developed for measuring the phase separation temperature Ts of polystyrene (PS) / poly(vinyl methyl ether) (PVME) blends [J. Polym. Sci., Part B 2012, 50, 250-256], we investigate the change in Ts due to the presence of electric fields. We show that electric fields strongly enhance mixing in PS/PVME polymer blends. For example, for a 50/50 PS/PVME blend composition, Ts is increased by over 10 K for electric fields of 18 kV/mm. [Preview Abstract] |
Friday, March 7, 2014 9:12AM - 9:24AM |
Y19.00007: Efficacy of Different Block Copolymers in Facilitating Microemulsion Phases in Polymer Blend Systems Gunja Pandav, Venkat Ganesan Polymeric microemulsions are formed in a narrow range of phase diagram when a blend of immiscible homopolymers is compatibilized by copolymers. In this study, we consider the ternary blend system of A and B homopolymers mixed with block copolymers containing A and B segments, and probe the efficacy of different copolymer configurations in promoting the formation of microemulsion phases. Specifically, we consider: (a) Monodisperse diblock copolymers; (b) Diblock copolymers with bidisperse molecular weights (MW); (c) Block copolymers having MW polydispersity in one of the blocks; (d) Diblock copolymers having monodisperse MW but bidispersity in average composition; and (e) Gradient copolymers exhibiting a linear variation in the average composition. Using single chain in mean field simulations effected in two dimensions, we probe the onset of formation and the width of the bicontinuous microemulsion channel in the ternary phase diagram of homopolymer blended with compatibilizer. We rationalize our results by explicitly quantifying the interfacial activity and the influence of fluctuation effects in the respective copolymer systems. [Preview Abstract] |
Friday, March 7, 2014 9:24AM - 9:36AM |
Y19.00008: Effective Blending of Ultrahigh Molecular Weight Polyethylene with High-Density Polyethylene via Solid-State Shear Pulverization (SSSP) Mirian Diop, John Torkelson Compared with conventional polyolefins, ultrahigh molecular weight polyethylene (UHMWPE) possesses outstanding mechanical properties, including impact strength and crack resistance, that make it it highly desirable for applications ranging from body armor to implants. Unfortunately, UHMWPE has an ultrahigh melt viscosity that renders common melt processes ineffective for making products from UHMWPE. Attempts to overcome this problem by blending UHMWPE with polyethylene (PE) by conventional melt mixing have been unsuccessful because of the enormous viscosity mismatch between blend components and have led to large suspensions of UHMWPE particles within a PE matrix. Here, we show the utility of solid-state shear pulverization (SSSP) in achieving effectively and intimately mixed UHMWPE/PE blends. For blends with up to 50 wt{\%} UHMWPE we observe only slight increases in viscosity ($\eta )$ at high shear rates but major increases in $\eta $ with increasing UHMWPE content at low shear rates. Using extensional rheology, we confirm the strain hardening behavior of SSSP blends. Additionally, shear rheology and differential scanning calorimetry data indicate that the degree of mixing between UHMWPE and HDPE domains can be increased dramatically with subsequent passes of SSSP and single screw extrusion. Finally, blends prepared via SSSP show dramatic increases in impact strength; e.g., for a 30/70 wt{\%} UHMWPE/HDPE blend, impact strength increases by about 300 {\%} (relative to the parent neat HDPE). [Preview Abstract] |
Friday, March 7, 2014 9:36AM - 9:48AM |
Y19.00009: Component Dynamics and the Corresponding Compositional Heterogeneity in Bulk and Thin Film Miscible Polymer Blends Hengxi Yang, Peter Green Miscible polymer blends are known to be compositional heterogeneous, due to self-concentration and thermally driven compositional fluctuation. In this work we investigate the segmental dynamics of poly(vinyl methyl ether) (PVME) in miscible polymer blends of polystyrene (PS) and PVME, using broadband dielectric spectroscopy, and manifest the correspondence between the component dynamics and the compositional heterogeneity in miscible blends. A single $\alpha $-relaxation is observed at high temperatures, $T$, obeying Vogel-Fulcher relation, whereas two separate relaxations exist at low $T$. One relaxation, slower and exhibiting a strong $T$-dependence, is associated with an average local composition with smaller PVME fraction. The other relaxation, known as $\alpha '$-relaxation, is weakly $T$-dependent and Arrhenius-like at low $T$; it reflects the PVME-rich domains within the confines of glassy PS-rich domains. In PVME/PS thin films confined between aluminum (Al) substrates, an additional relaxation process, due to PVME chains that preferentially segregated to Al interfaces, emerges. [Preview Abstract] |
Friday, March 7, 2014 9:48AM - 10:00AM |
Y19.00010: Biodegradability and mechanical properties of poly(butylene succinate) composites with finely dispersed hydrophilic poly(acrylic acid) Sawako Mizuno, Atsushi Hotta Biodegradability and mechanical properties of aliphatic poly(butylene succinate) (PBS) films with finely dispersed hydrophilic poly(acrylic acid) (PAA) were investigated. First, 3.5 wt{\%} of PAA was chemically grafted onto the surface of the PBS films (surface-grafted PBS) by photo grafting polymerization, and then the grafted PAA was homogeneously and finely dispersed into PBS by dissolving the surface-grafted PBS into chloroform before mixing and drying to get solid PAA-dispersed PBS. Degradation of these modified PBS was investigated using gel permeation chromatography (GPC) and tensile testing. According to the GPC results, it was found that the PAA-dispersed PBS had intermediate biodegradability with the intermediate water intake, and the reaction constant of PAA-dispersed PBS was in between those of untreated PBS and surface-grafted PBS, in fact 25{\%} higher and 17{\%} lower, respectively. The experimental results presented that the biodegradability of PBS could be well controlled by the dispersion of PAA, possibly leading to the widespread use of PBS for biodegradable polymers. [Preview Abstract] |
Friday, March 7, 2014 10:00AM - 10:12AM |
Y19.00011: Block copolymer toughened epoxy: Theory and experiment Carmelo Declet-Perez, Lorraine Francis, Frank Bates We have recently combined small angle x-ray scattering and tensile experiments to follow real-time deformation of block copolymer nanostructures in order to understand toughness enhancement in block copolymer modified epoxies. Our experiments provided direct evidence of internal cavitation in rubbery nanodomains. In this presentation we show that our observations are consistent with the predictions from an energy balance-based cavitation criteria recently modified by Bucknall and Paul [Polymer \textbf{50}, 5539 (2009) \& Polymer \textbf{54}, 320 (2013)]. [Preview Abstract] |
Friday, March 7, 2014 10:12AM - 10:24AM |
Y19.00012: Collective dynamic response of bound polymer chains to nanofillers in a good solvent Tad Koga, Naisheng Jiang, Maya Endoh, Tomomi Masui, Hiroyuki Kishimoto, Takashi Taniguchi, Michihiro Nagao As proposed initially by Stickney and Falb, a bound polymer covers the surface of filler particles with a stable layer of macromolecules via van der Walls interactions and is thus resistant to dissolution even in a good solvent. The most thorough experimental and theoretical studies on bound polymer layers (BPLs) have been carried out for carbon black (CB)-filled rubber systems. However, a molecular scale description of real chain conformations/dynamics within such a very thin BPL (typically 1-5 nm in thickness) remains unsolved due to the lack of methods capable of providing high-resolution structural information. Here we present small-angle neutron scattering and neutron spin-echo spectroscopy results for bound polybutadiene (PB, M$_{w}$ = 38,000) chains to the CB surface in toluene. To label the bound layer for the neutron scattering experiments, deuterated toluene, which has the nearly same scattering length density as that of CB, was used. We will highlight the unique collective dynamic response of the bound polymer chains in the good solvent. [Preview Abstract] |
Friday, March 7, 2014 10:24AM - 10:36AM |
Y19.00013: Fluctuation/Correlation Effects on the Phase Behavior of Incompressible Polymer Blends Quantified by Fast Lattice Monte Carlo Simulations Pengfei Zhang, Qiang Wang Fast lattice Monte Carlo (FLMC) simulations [Q. Wang, \textbf{Soft Matter 5}, 4564 (2009); \textbf{6}, 6206 (2010)] with multiple occupancy of lattice sites and Kronecker $\delta $-function interactions give orders of magnitude faster/better sampling of configuration space for many-chain systems than conventional lattice MC simulations with the self- and mutual- avoiding walk and nearest-neighbor interactions. Adapting the cooperative motion algorithm to a lattice with multiple occupancy, we studied incompressible and symmetric binary polymer blends using FLMC simulations in a semi-grand canonical ensemble with replica exchange and multiple histogram reweighting, and performed finite-size scaling analysis of our simulation results. Comparing the critical point and binodal curve obtained from FLMC simulations with the predictions from the corresponding Flory-Huggins (FH) and Gaussian-fluctuation (GF) theories, all based on the same model system and thus without any parameter-fitting, we unambiguously quantified the effects of fluctuations/correlations neglected in FH theory and treated approximately in GF theory. [Preview Abstract] |
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