Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session M43: Focus Session: Industry Day: Applied Polymer Physics in Advanced Manufacturing |
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Sponsoring Units: DPOLY FIAP Chair: Brent Neal, Milliken & Company Room: 214C |
Wednesday, March 4, 2015 11:15AM - 11:27AM |
M43.00001: Detection of pharmaceutical crystals in polymer particles by transmission electron microscopy Ralm Ricarte, Marc Hillmyer, Timothy Lodge The use of solid dispersions, blends of an active pharmaceutical ingredient (API) and a polymer excipient, may significantly enhance the dissolution performance of a poorly water soluble drug. However, the polymer's role in inhibiting API crystallization within the solid dispersion is not well understood. One of the main challenges in elucidating this mechanism is the difficulty of detecting small amounts of API crystals (less than 5 volume percent) within the polymer matrix. In this work, we explore the use of transmission electron microscopy (TEM) to characterize the crystallinity of griseofulvin (GF) in hydroxypropyl methylcellulose acetate succinate (HPMCAS) solid dispersions. Using both real-space images and electron diffraction patterns from TEM, GF crystals in the HPMCAS matrix were unambiguously identified with nanometer resolution and with a crystal detection sensitivity superior to both wide-angle X-ray scattering and differential scanning calorimetry. TEM shows great potential for characterizing even trace API crystallinity in solid polymeric dispersions. [Preview Abstract] |
Wednesday, March 4, 2015 11:27AM - 11:39AM |
M43.00002: Colloidal Aggregate Structure under Shear by USANS Tirtha Chatterjee, Antony K. Van Dyk, Valeriy V. Ginzburg, Alan I. Nakatani Paints are complex formulations of polymeric binders, inorganic pigments, dispersants, surfactants, colorants, rheology modifiers, and other additives. A commercially successful paint exhibits a desired viscosity profile over a wide shear rate range from 10$^{-5}$ s$^{-1}$ for settling to \textgreater 10$^{4}$ s$^{-1}$ for rolling, and spray applications. Understanding paint formulation structure is critical as it governs the paint viscosity profile. However, probing paint formulation structure under shear is a challenging task due to the formulation complexity containing structures with different hierarchical length scales and their alterations under the influence of an external flow field. In this work mesoscale structures of paint formulations under shear are investigated using Ultra Small-Angle Neutron Scattering (rheo-USANS). Contrast match conditions were utilized to independently probe the structure of latex binder particle aggregates and the TiO$_{2}$ pigment particle aggregates. Rheo-USANS data revealed that the aggregates are fractal in nature and their self-similarity dimensions and correlations lengths depend on the chemistry of the binder particles, the type of rheology modifier present and the shear stress imposed upon the formulation. These results can be explained in the framework of diffusion and reaction limited transient aggregates structure evolution under simple shear. [Preview Abstract] |
Wednesday, March 4, 2015 11:39AM - 11:51AM |
M43.00003: Parameterization and Adsorption Study of Hydrophobic Ethoxylated Urethane (HEUR) using Coarse-Grained MD Simulations with Implicit Water Shihu Wang, Ronald G. Larson, Valeriy V. Ginzburg We parameterize a coarse-grained (CG) model using implicit water for a model Hydrophobic Ethoxylated Urethane (HEUR) composed of poly(ethylene oxide) (PEO) endcapped with hydrocarbon tails. Our model matches predictions using a CG Martini model with explicit water for PEO in water. We illustrate the strong adsorption of PEO onto hydrocarbon surfaces in water and obtain parameters for PEO at hydrocarbon/water interfaces. As a validation, we simulate the self-assembly of alkyl poly(ethylene glycol) surfactants and observe the transition from a lamellar phase to cylindrical micelles upon varying EO length, a result in agreement with previous studies. Lastly, we study the adsorption of HEURs onto hydrophobic surfaces. We observe bridge formation between two surfaces, interconnected flower-like micelles and their subsequent adsorption, in equilibrated systems. We discuss the influence of hydrophobe length and HEUR volume fraction on the adsorption process and the equilibrium adsorption. These results provide important insights for HEURs adsorption and are useful for comparisons with Self-Consistent Field Theory. [Preview Abstract] |
Wednesday, March 4, 2015 11:51AM - 12:03PM |
M43.00004: Modeling the Adsorption of Hydrophobic Ethoxylated Urethane (HEUR) Thickeners onto Latex Surfaces using Self-Consistent Field Theory Valeriy Ginzburg, Antony Van Dyk, Tirtha Chatterjee, Shihu Wang, Ronald Larson Hydrophobic Ethoxylated Urethane (HEUR) polymers are widely used as rheology modifiers (thickeners) in waterborne latex paints. Recently, it has been shown that the thickening effect of HEURs in paints is largely determined by their adsorption onto latex surfaces, this adsorption being a function of polymer structure, latex surface chemistry, and total available latex surface. Here, we describe the application of Self-Consistent Field Theory (SCFT) to calculate adsorption isotherms of several model HEURs onto ideal hydrophobic latex surfaces. Unlike earlier SCFT studies of adsorption, we explicitly take into account the role of HEUR micelles and competition between adsorption and micellization. The results are compared with experimental data and coarse-grained molecular dynamic (CG-MD) simulations, and good qualitative and semi-quantitative agreement is found. [Preview Abstract] |
Wednesday, March 4, 2015 12:03PM - 12:15PM |
M43.00005: Atomistic Molecular Dynamics Simulations of the Electrical Double Zifeng Li, Scott Milner, Kristen Fichthorn The electrical double layer (EDL) near the polymer/water interface plays a key role in the colloidal stability of latex paint. To elucidate the structure of the EDL at the molecular level, we conducted an all-atom molecular dynamics simulations. We studied two representative surface charge groups in latex, the ionic surfactant sodium dodecyl sulfate (SDS) and the grafted short polyelectrolyte charged by dissociated methyl methacrylic acid (MAA) monomers. Our results confirm that the Poisson-Boltzmann theory works well outside the Stern layer. Our calculated electrostatic potential at the Outer Helmholtz Plane (OHP) is close to the zeta potential measured experimentally, which suggests that the potential at the OHP is a good estimate of the zeta potential. We found that the position of the OHP for the MAA polyelectrolyte system extends much further into the aqueous phase than that in the SDS system, resulting in a Stern layer that is twice as thick. This model will allow for future investigations of the interactions of the surface with different surfactants and rheology modifiers, which may serve as a guide to tune the rheology of latex formulations. [Preview Abstract] |
Wednesday, March 4, 2015 12:15PM - 12:27PM |
M43.00006: Interdiffusion of Polycarbonate in Fused Deposition Modeling Welds Jonathan Seppala, Aaron Forster, Sushil Satija, Ronald Jones, Kalman Migler Fused deposition modeling (FDM), a now common and inexpensive additive manufacturing method, produces 3D objects by extruding molten polymer layer-by-layer. Compared to traditional polymer processing methods (injection, vacuum, and blow molding), FDM parts have inferior mechanical properties, surface finish, and dimensional stability. From a polymer processing point of view the polymer-polymer weld between each layer limits the mechanical strength of the final part. Unlike traditional processing methods, where the polymer is uniformly melted and entangled, FDM welds are typically weaker due to the short time available for polymer interdiffusion and entanglement. To emulate the FDM process thin film bilayers of polycarbonate/d-polycarbonate were annealed using scaled times and temperatures accessible in FDM. Shift factors from Time-Temperature Superposition, measured by small amplitude oscillatory shear, were used to calculate reasonable annealing times (min) at temperatures below the actual extrusion temperature. The extent of interdiffusion was then measured using neutron reflectivity. Analogous specimens were prepared to characterize the mechanical properties. FDM build parameters were then related to interdiffusion between welded layers and mechanical properties. Understating the relationship between build parameters, interdiffusion, and mechanical strength will allow FDM users to print stronger parts in an intelligent manner rather than using trial-and-error and build parameter lock-in. [Preview Abstract] |
Wednesday, March 4, 2015 12:27PM - 12:39PM |
M43.00007: Elasticity and Extensibility Determine Printability and Spinnability of Polymer Solutions Jelena Dinic, Leidy Nallely Jimenez, Vicky Mei, Yiran Zhang, Vivek Sharma Many advanced manufacturing technologies like inkjet printing, 3D printing, nano-fiber spinning, gravure printing and nanoimprint lithography involve complex free-surface flows, where both shear and extensional rheology affect processability. In applications that involve progressive thinning and break-up of a fluid column or sheet into drops, the dominant flow within the filament is extensional in nature. Polymeric fluids exhibit a much larger resistance to flow in an elongational flow field than Newtonian fluids with same shear viscosity. Characterizing the filament thinning and break-up kinetics in jetting, dripping and stretching liquid bridge provides invaluable insight into the interplay of elastic, viscous, capillary and inertial stresses relevant for these applications. In this talk, we elucidate how polymer composition, flexibility and molecular weight determine the kinetics of capillary-driven thinning and pinch-off in our experiments. Both effective relaxation time and transient extensional viscosity are found to be strongly concentration dependent even for dilute solutions. Further, we show how finite extensibility of polymers dramatically changes the kinematics from elastocapillary to viscocapillary under strong extensional flow fields that can lead to coil-stretch transition. [Preview Abstract] |
Wednesday, March 4, 2015 12:39PM - 12:51PM |
M43.00008: Controlling Fiber Morphology in Simultaneous Centrifugal Spinning and Photopolymerization Yichen Fang, Austin Dulaney, Christopher Ellison Current synthetic fiber manufacturing technologies use either solvent or heat to transform a solid preformed polymer into a liquid before applying a force to draw the liquid into fiber. While the use of solvent poses concerns regarding process safety and environmental impact, the use of heat may also lead to polymer degradation and excessive energy consumption. To address these critical challenges, here we present an alternative fiber manufacturing method that encompasses extruding a monomer solution through an orifice, drawing it using centrifugal Forcespinning and polymerizing the monomer jet into solid fiber in flight using UV initiated thiol-ene chemistry. This method not only negates the use of both heat and solvent, but also produces fibers that are highly crosslinked, mechanically robust, and thermally stable. In this process, the balance between curing kinetics, fiber flight time, and solution viscoelasticity is essential. Studies were conducted to quantitatively investigate the effect of these factors on fiber formation and morphology. An operating diagram was developed to show how the intricate interplay of these factors led to the formation of smooth fibers and other undesirable fiber defects, such as beads-on-string, fused fibers, and droplets. [Preview Abstract] |
Wednesday, March 4, 2015 12:51PM - 1:03PM |
M43.00009: Engineering the Crystalline Morphology of Polymer Thin Films at a Molecular Level via Matrix Assisted Pulsed Laser Evaporation Hyuncheol Jeong, Craig Arnold, Rodney Priestley Controlling the crystalline morphology of polymeric thin films at a molecular level has been increasingly important due to their potential as the active layer in organic electronics. Typically, the crystalline morphology in films is achieved via thermal annealing or melt-crystallization of spin-cast polymers. This approach often leads to a spherulitic morphology where the crystalline lamellae grow in all directions. Here, we introduce an alternative approach to make crystalline polymer films via Matrix Assisted Pulsed Laser Evaporation (MAPLE). Using polyethylene oxide (PEO) as a model polymer, we show that the preferential orientation of polymer crystals can be controlled during the film growth. By laser-ablating a frozen dilute solution of the desired polymer, MAPLE provides a non-destructive means for the deposition of polymer films. Due to the liquid nature of as-deposited polymers confined in nanodroplets, this technique can exploit the substrate effect on the crystal nucleation and growth of nano-confined polymers during the film growth. Mimicking the epitaxial growth of metallic films, this novel polymer deposition technique may enable the engineering of film properties in a way not achievable in bulk. [Preview Abstract] |
Wednesday, March 4, 2015 1:03PM - 1:15PM |
M43.00010: Coupling frontal photopolymerization and surface instabilities for a novel 3D patterning technology Alessandra Vitale, Matthew Hennessy, Omar Matar, Jack Douglas, Jo\~ao Cabral Patterning of soft matter provides an exceptional route for the generation of micro/nanostructured and functional surfaces. We describe a new 3D fabrication process based on coupling frontal photopolymerization (FPP) with precisely controlled, yet spontaneous, interfacial wrinkling. FPP is a complex spatio-temporal process that can lead to well-defined propagating fronts of network formation, both stable and unstable. We investigate this process focusing on the interfacial monomer-to-polymer conversion profile and its wave propagation. A simple coarse-grained model is found to describe remarkably well the planar frontal logarithmic kinetics, capturing the effects of UV light exposure time (or dose) and temperature, as well as the front position. In defined conditions, surface instabilities are introduced and interfere with wave planarity, resulting in the formation of ``minimal'' surfaces with complex 3D geometries. Building on this understanding on the propagation of wavefronts of network formation during photopolymerization, we demonstrate the design and fabrication of 3D patterned polymer materials with tunable shapes with optical and surface functionality. [Preview Abstract] |
Wednesday, March 4, 2015 1:15PM - 1:27PM |
M43.00011: Improving information density in ferroelectric polymer films by using nanoimprinted gratings Daniel E. Mart\'Inez-Tong, Michela Soccio, Daniel R. Rueda, Aurora Nogales, Mari Cruz Garc\'Ia-Guti\'errez, Tiberio A. Ezquerra The development of polymer non-volatile memories depends on the effective fabrication of devices with high density of information. Well-defined low aspect ratio nanogratings on thin films of poly(vinylidene fluoride--trifluoroethylene) copolymers can be fabricated by using Nanoimprint Lithography (NIL). By using these nanogratings, an improved management of writing and reading information can be reached as revealed by Piezoresponse Force Microscopy (PFM). Structural investigation by means of Grazing Incidence X-ray (GIX) scattering techniques indicates that the physical confinement generated by nanoimprint promotes the development of smaller and edge-on oriented crystals. Our results evidence that one-dimensional nanostructuring can be a straightforward approach to improve the control of the polarization in ferroelectric polymer thin films. [Preview Abstract] |
Wednesday, March 4, 2015 1:27PM - 1:39PM |
M43.00012: Liquid filament instability due to stretch-induced phase separation in polymer solutions Arkadii Arinstein, Valery Kulichikhin, Alexander Malkin The instability in a jet of a viscoelastic semi-dilute entangled polymer solution under high stretching is discussed. Initially, the variation in osmotic pressure can compensate for decrease in the capillary force, and the jet is stable. The further evolution of the polymer solution along the jet results in formation of a filament in the jet center and of a near-surface solvent layer. Such a redistribution of polymer seems like a ``phase separation'', but it is related to stretching of the jet. The viscous liquid shell demonstrates Raleigh-type instability resulting in the formation of individual droplets on the oriented filament. Experimental observations showed that this separation is starting during few first seconds, and continues of about 10$-$15 seconds. The modeling shows that a jet stretching results in a radial gradient in the polymer distribution: the polymer is concentrated in the jet center, whereas the solvent is remaining near the surface. The key point of this model is that a large longitudinal stretching of a polymer network results in its lateral contraction, so a solvent is pressed out of this polymer network because of the decrease in its volume. [Preview Abstract] |
Wednesday, March 4, 2015 1:39PM - 2:15PM |
M43.00013: 3D Printing of Personalized Organs and Tissues. Invited Speaker: Kaiming Ye Authors: Kaiming Ye and Sha Jin, Department of Biomedical Engineering, Watson School of Engineering and Applied Science, Binghamton University, State University of New York, Binghamton, NY 13902-6000 Abstract: Creation of highly organized multicellular constructs, including tissues and organs or organoids, will revolutionize tissue engineering and regenerative medicine. The development of these technologies will enable the production of individualized organs or tissues for patient-tailored organ transplantation or cell-based therapy. For instance, a patient with damaged myocardial tissues due to an ischemic event can receive a myocardial transplant generated using the patient’s own induced pluripotent stem cells (iPSCs). Likewise, a type-1 diabetic patient can be treated with lab-generated islets to restore his or her physiological insulin secretion capability. These lab-produced, high order tissues or organs can also serve as disease models for pathophysiological study and drug screening. The remarkable advances in stem cell biology, tissue engineering, microfabrication, and materials science in the last decade suggest the feasibility of generating these tissues and organoids in the laboratory. Nevertheless, major challenges still exist. One of the critical challenges that we still face today is the difficulty in constructing or fabricating multicellular assemblies that recapitulate in vivo microenvironments essential for controlling cell proliferation, migration, differentiation, maturation and assembly into a biologically functional tissue or organoid structure. These challenges can be addressed through developing 3D organ and tissue printing which enables organizing and assembling cells into desired tissue and organ structures. We have shown that human pluripotent stem cells differentiated in 3D environments are mature and possess high degree of biological function necessary for them to function in vivo. [Preview Abstract] |
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