Bulletin of the American Physical Society
2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009; Pittsburgh, Pennsylvania
Session W19: The Physics of Polymer Nanocomposites: Grafting and Dispersion |
Hide Abstracts |
Sponsoring Units: DPOLY Chair: Arthi Jayaraman, University of Colorado, Boulder Room: 320 |
Thursday, March 19, 2009 11:15AM - 11:27AM |
W19.00001: A theoretical study of polymer grafted nanoparticles as fillers in polymer nanocomposites Arthi Jayaraman, Kenneth Schweizer We have generalized the microscopic Polymer Reference Interaction Site Model (PRISM) theory to study the structure and phase behavior of polymer-tethered spherical nanoparticles (fillers) in a homopolymer matrix. In the absence of a polymer matrix, melts of polymer-tethered nanoparticles show strong concentration fluctuations indicative of aggregate formation and/or a tendency for microphase separation as the total packing fraction and/or nanoparticle attraction strength increase. In the presence of a polymer matrix there is competition between nanoparticle attractions, steric repulsion between grafted polymers, and polymer matrix induced depletion-like attraction. For single tethered particles, volume of the tether being equal to the volume of the nanoparticle, the apparent microphase spinodal curve exhibits both dilution-like and depletion-like features, and a non-monotonic dependence on matrix chain length. As the particle size and tether length are increased, such that the total space filling volume of the tether continues to equal the nanoparticle volume, the shape of the microphase spinodal curve remains unchanged, but the effect of matrix polymer chain length on the spinodal temperature diminishes. The effect of various parameters on the spinodal temperature will be presented. [Preview Abstract] |
Thursday, March 19, 2009 11:27AM - 11:39AM |
W19.00002: Highly-branched anisotropic hybrid nanoparticles at surfaces. Vladimir Tsukruk We present a brief overview of our recent studies on combined hybrid anisotropic structures composed of inorganic nanoparticles and highly branched molecules such as modified silsesquioxanes polyhedra cores (POSS) with mixed hydrophobic-hydrophilic tails and silver nanowires with functionalized star block copolymer with embedded gold nanoparticles (nanocobs). We demonstrate two-stage melting of that branched POSS and their ability to form monolayer and multilayered LB structures. On the other hand, we observed that silver-BCP-gold nanocobs display extremely bright Raman scattering caused by surface enhanced Raman effect with very different longitudinal and transversal optical properties as revealed by high-resolution confocal Raman microscopy. To study these hybrid nanostructures we applied combined AFM, SEM, TEM, XPS, SERS, UV-vis, and XR techniques. [Preview Abstract] |
Thursday, March 19, 2009 11:39AM - 11:51AM |
W19.00003: Particle Dynamics within Self-Assembling Polymer-Grafted Spherical Nanoparticles Pinar Akcora, Sanat K. Kumar, Yu Li, Brian Benicewicz, Suresh Narayanan We have recently shown that the self-assembly of polymer grafted spherical nanoparticles can be achieved by varying the brush grafting density and chain length. The mechanical behavior of these nanocomposites with various states of particle dispersion has been explored using x-ray photon correlation spectroscopy. Nanoscale and macroscopic dynamic measurements show that mechanical reinforcement results from the percolated and also strongly entangled brushes forming strong networks. Particle dynamics within various polymeric nanostructures will be discussed. [Preview Abstract] |
Thursday, March 19, 2009 11:51AM - 12:03PM |
W19.00004: Thermally Stable Au Nanoparticles via Photo-crosslinkable Polymeric Stabilizers Joona Bang, Misang Yoo, Bumjoon J. Kim Polymer nanocomposites consisting of polymers and inorganic nanoparticles (NPs) have attracted many interest due to their applications such as solar cell, sensors, catalysts and ferroelectric devices. To integrate NPs into polymer matrix in the controlled manner, thiol-terminated stabilizers have been used to tune the surface property of NPs such as Au, Pt, CdSe, etc. However, a practical use of such particles in the nanocomposites is very limited by thermal instability even at $\sim $90 $^{\circ}$C, leading to the agglomeration of NPs. To impart the thermal stability of NPs, we modified Au NPs surface using UV-crosslinkable polymeric stabilizers. After UV-crosslinking, it was found that the Au NPs exhibit the excellent stability at high temperature ($\sim $180 $^{\circ}$C) in both solution and thin-film states. Furthermore, we demonstrate that thermally stable Au NPs can be used as compatibilizers in PS/PMMA blends. The NPs at the PS/PMMA interface produced the dramatic reduction in the droplet size after 1 day of thermal annealing at 180 $^{\circ}$C, in which the particle size is unchanged. [Preview Abstract] |
Thursday, March 19, 2009 12:03PM - 12:15PM |
W19.00005: Design of Polymer-Grafted Particles for Biocompatability David Trombly, Venkat Ganesan Drug designers often coat drug particles with grafted polymers in order to introduce a net repulsion between the particles and blood proteins. This net repulsion results from the energy cost of compressing grafted chains on approach of proteins. It thus overcomes the Van Der Waals attraction between drug and protein which would otherwise cause particle-protein agglomeration and ultimately thrombosis. This study proposes to develop a fundamental understanding of the role of different features in controlling the efficacy of the grafted layers. We address this issue by developing a framework to predict the interactions between a polymer-coated spherical particle and a bare spherical particle. In order to fully capture the two-sphere system, a numerical solution of polymer mean field theory is used in a bispherical coordinate system. Results for protein-particle interaction energies for different design parameters will be presented. For biological applications, polyethylene glycol is often used as the grafted polymer. The unique properties of this molecule will be accounted for using the n-cluster model. [Preview Abstract] |
Thursday, March 19, 2009 12:15PM - 12:27PM |
W19.00006: Synthesis of Polystyrene-Silica Composite Particles via One-Step Nanoparticle-Stabilized Emulsion Polymerization Lenore Dai, Huan Ma Polystyrene-silica core-shell composite particles are prepared by one-step emulsion polymerization with a nonionic initiator VA-086, solely stabilized by silica nanoparticles. The silica nanoparticles are successfully incorporated into as the shell, likely due to the fact that the nanoparticles are thermodynamically favorable to self-assemble and remain at the liquid-liquid interfaces during the emulsion polymerization. The silica content, determined by thermogravimetric analysis, is approximately 20 wt% in the composite particles. In addition, we further explore the polymerization mechanism by studying the particle growth as a function of initiator concentration and reaction time: when the silica/monomer ratio is increased from 0.83 wt% to 2.5 wt%, the particle size at 24 hour reaction time decreases for a fixed monomer amount, probably due to a larger number of nuclei at the initial stage of polymerization. Further increasing the initiator/monomer ratio to 4.2 wt% does not continually decrease the particle size, which may be limited by the stabilization provided by a fixed concentration of silica nanoparticles. The surface coverage also changes with initiator concentration and reaction time although the underlying mechanism is not fully understood. [Preview Abstract] |
Thursday, March 19, 2009 12:27PM - 12:39PM |
W19.00007: Effects of Grafted Chain Density on Nanoparticle and Melt Structure Joshua Kalb, Sanat Kumar, Robert S. Hoy, Gary S. Grest Applications of nanoparticles have increased dramatically over the last few years with uses ranging from scratch proof glass to lubricants to fighting cancer. Grafting polymer chains to these systems further increases the range of their properties, but still much remains to understand about the behavior of 'brush grafted nanoparticle' systems, particularly in their interaction and entanglement with a polymer melt. Previous works where polymer brushes were attached to a flat surface have demonstrated that entanglements between the attached chains and the polymer melt depend strongly on coverage and length of the attached chains. Allowing for a curved grafted nanoparticle surface allows for a wider range of interactions with the melt. Here we present molecular dynamics simulations of the structure of grafted nanoparticles and their entanglements~with a highly entangled melt. Individual entanglements are identified using a modified version of primitive path analysis. [Preview Abstract] |
Thursday, March 19, 2009 12:39PM - 12:51PM |
W19.00008: Polyethylene/organically-modified layered-silicate nanocomposites with antimicrobial activity P. Songtipya, M.M. Jimenez-Gasco, E. Manias Despite the very intensive research on polymer nanocomposites, the opportunities for new functionalities possible by nanofillers still remain largely untapped. Here, we present polyethylene/inorganic nanocomposites that exhibit strongly enhanced mechanical performance and, at the same time, also an antimicrobial activity originating from the organo-filler nature. Specifically, PE/organically-modified layered-silicate nanocomposites were prepared via melt-processing, and antimicrobial activity was designed by proper choice of their organic modification. Their antimicrobial activity was measured against three micotoxinogen fungal strains (\textit{Penicillium roqueforti} and \textit{claviforme}, and \textit{Fusarium graminearum}) as model soil-borne plant and food contaminants. Montmorillonite-based organofillers, which only differ in their organic modification, were used to exemplify how these surfactants can be designed to render antifungal activity to the nanocomposites. The comparative discussion of the growth of fungi on unfilled PE and nanocomposite PE films is used to demonstrate how the antimicrobial efficacy is dictated by the surfactant chemistry and, further, how the nanocomposites' inhibitory activity compares to that of the organo-fillers and the surfactants. [Preview Abstract] |
Thursday, March 19, 2009 12:51PM - 1:03PM |
W19.00009: Modeling of block copolymer/nanoparticle nano-composites Marco Pinna, Ignacio Pagonabarraga, Andrei Zvelindovsky We develop a coarse grained simulation technique to study dynamics in soft nano-composites. The system consists of block copolymer melt with embedded nano-size particles. The time evolution of the system is described by a hybrid method combining a field based simulation for block copolymer component and a particle based method for nano-colloids. The block copolymer is modelled by cell dynamics simulation technique, and nano-particles are modelled as soft particles with prescribed density profile. A cross interaction term is controlling the interplay of dynamics of both components. The influence of nano-particles on block copolymer morphology is investigated. [Preview Abstract] |
Thursday, March 19, 2009 1:03PM - 1:15PM |
W19.00010: Interfacial Slip in Polymer Blends with Nanoparticles Joseph Ortiz, Eihab Jaber, Dilip Gersappe The interfacial region in polymer blends has been identified as a low viscosity region in which considerable slip can occur when the blend is subjected to shear forces. Here we use Molecular Dynamics simulations to establish the role that added nanoparticle fillers play in modifying the interfacial rheology. By choosing conditions under which the fillers are localized, either in the two phases or at the interface, we can look at the interplay between the strengthening capability of nanoparticles and the change in the interfacial slip behavior. We examine particle size, attraction between the particle and the polymer component, and the amount of filler in the material. Our studies are performed both above and below the point at which the filler particles form a transient network in the blend. [Preview Abstract] |
Thursday, March 19, 2009 1:15PM - 1:27PM |
W19.00011: Synthesis of composite polymer nanoparticles . Edward Van Keuren, Maki Nishida We have been developing composite nanoparticles using the reprecipitation method or miniemulsion polymerization. These methods enable the combination of multiple functional components, such as large metal or metal oxide clusters and molecular species such as fluorophores, into polymer nanoparticles. The incorporation of these into the polymer or monomer precursors requires a detailed understanding of the mutual solubility of the components. We present fluorescence correlation spectroscopy measurements of molecular solubility and results from dynamic light scattering, electron microscopy and Raman spectroscopy that reveal the morphology and composition of these particles. [Preview Abstract] |
Thursday, March 19, 2009 1:27PM - 1:39PM |
W19.00012: Relaxation behaviors of nanoparticles in polymer composites: influence of local frictions by polymer chains Byeongdu Lee, PAPPANNAN Thiyagarajan, Suresh Narayanan, Alec Sandy, Vilas Pol, Chieh-Tsung Lo, David Bohnsack The dynamics of Au nanoparticles (AuNP) tethered with thiol-terminated polystyrene (PS) in the composites with poly(styrene-b-2-vinylpyridine) diblock copolymers (PS-PVP) have been studied by x-ray photon correlation spectroscopy and small-angle x-ray scattering. Relaxation behaviors of nanoparticles located selectively in PS domain due to enthalpic interaction, interestingly, are not correlated with those of matrix polymer chains, i.e., their relaxation times are not dependent on the molecular weights of PS-PVP. They relax faster in PS-PVP than in PS homopolymer having the same molecular weight as the PS brush of PS-PVP. On the other hand, the influence of morphological structures of PS-PVP, however, is significant: AuNP moves faster in the lamellae phase than those in the cylinder phase. [Preview Abstract] |
Thursday, March 19, 2009 1:39PM - 1:51PM |
W19.00013: Nano-particle distribution in a polymer nano-composite Panagiotis Maniadis, Ioannis N. Tsimpanogiannis, Edward M. Kober, Turab Lookman We use the hybrid particle-Self Consistent Field calculation (hybrid particle-SCF) to study the distribution of particles in a multi-block copolymer nano-composite. Using the static approach, we first find the effective interaction potential between the nano-particles and the polymer. The interaction has an entropic and an enthalpic component. The dynamical simulation confirms that the distribution of particles has a maximum at the minima of the interaction potential. We also study the situation where the nano-particles are distributed in a blend of AB diblock and A homopolymer. In this case, for large homopolymer concentration (larger than 20\%), an interface is created between components that are identical, but they come from different types of polymer chains (i.e. the AB diblock or the A homopolymer). We find that the interaction potential has a minimum in this A/A interface which is of pure entropic origin. Furthermore the dynamical simulation reveals that the distribution of nano-particles has a maximum in the area around this interface. [Preview Abstract] |
Thursday, March 19, 2009 1:51PM - 2:03PM |
W19.00014: Thermoresponsive Self-Assembling Nanocomposites Kari Thorkelsson, Yue Zhao, Thomas Schilling, Alexander Mastroianni, Joseph M. Luther, Yue Wu, A. Paul Alivisatos, Ting Xu Nanoparticles have significant potential for use in fields including photovoltaics and memory storage, but to realize this potential, their distribution must be finely controlled. We present here a verstile method to achieve such control, using a diblock copolymer supramolecule composed of polystyrene-block-poly(4-vinylpyridene) (PS-b-P4VP) and 3-pentadecylphenol (PDP). The PDP hydrogen bonds to the P4VP block, forming a comb block. This change in morphology causes the PS-b-P4VP(PDP) supramolecule to force the nanoparticles into well-organized rows one nanoparticles thick at the center of the P4VP(PDP) domains. Furthermore, the morphology of the supramolecule-nanoparticle composite changes with temperature as hydrogen bonding is broken and the PDP becomes soluble in the PS block. This provides a useful path for the production of polymer-based thermoresponsive nanocomposites. [Preview Abstract] |
Thursday, March 19, 2009 2:03PM - 2:15PM |
W19.00015: Self-Assembly of Polymer-Decorated Nanoparticles in the Bulk and in a Nanometric Confinement Damien Maillard, Sanat Kumar, Pinar Akcora As shown previously by simulation and TEM studies in the bulk, PS grafted nanoparticles when mixed a PS matrix self-assemble into a range of superstructures. These self-assembled structures can be regrouped into a phase diagram in which the leading parameters are the particles grafting density and the molecular weight ratio of the grafted and free matrix chains. Depending on those parameters the particles can be well dispersed or aggregated in one (strings), two (interconnected sheets) or three (spherical aggregates) dimensions. Here we consider the corresponding behavior in thin films (100 nm thick) using in-situ phase contrast AFM. In addition to yielding the morphologies, this protocol allows us directly visualize the aggregation process of the particles. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700