Bulletin of the American Physical Society
APS March Meeting 2013
Volume 58, Number 1
Monday–Friday, March 18–22, 2013; Baltimore, Maryland
Session G32: Focus Session: Polymer Nanocomposites: Active Particles |
Hide Abstracts |
Sponsoring Units: DPOLY Chair: Russell Gorga, North Carolina State University Room: 340 |
Tuesday, March 19, 2013 11:15AM - 11:27AM |
G32.00001: Magnetic Field Driven Alignment of Cobalt Nanoparticles and Directional Strengthening Effect in Polystyrene Matrix Nanocomposites Hongyi Yuan, Jeffrey Pyun, Alamgir Karim Nanocomposite thin films of Polystyrene (PS) and PS-coated cobalt (Co) nanoparticles were prepared by solution-mixing and flow-coating. Ferromagnetic Co nanoparticles were either randomly dispersed or aligned in 1-D by applying a weak magnetic field during the flow-coating process. AFM and TEM images show nano-chain formation by self-assembly of the Co nanoparticles in the concentration range of 2-10 wt{\%} relative to PS in the presence of magnetic field. The technique of Strain-Induced Elastic Buckling Instability for Mechanical Measurements (SIEBIMM) was employed to determine the elastic moduli of neat PS and PS / Co nanocomposite thin films, which were calculated from the buckling patterns generated by applying and releasing tensile stresses. Strengthening effect was found in nanocomposite thin films depending on the alignment direction of the dispersed Co nanoparticles. The effect of shape and concentration of nanoparticles on the elastic modulus of nanocomposite thin films will be discussed. [Preview Abstract] |
Tuesday, March 19, 2013 11:27AM - 11:39AM |
G32.00002: Magnetic field gradient driven self-assembly of superparamagnetic nanoparticles using programmable magnetically-recorded templates L. Ye, B. Qi, T.G. Lawton, O.T. Mefford, C. Rinaldi, S. Garzon, T.M. Crawford Using the enormous magnetic field gradients (100 MT/m @ z$=$20 nm) present near the surface of magnetic recording media, we demonstrate the fabrication of diffraction gratings with lines consisting entirely of magnetic nanoparticles assembled from a colloidal fluid onto a disk drive medium, followed by transfer to a flexible and transparent polymer thin film. These nanomanufactured gratings have line spacings programmed with commercial magnetic recording and are inherently concave with radii of curvature controlled by varying the polymer film thickness. The diffracted intensity increases non-monotonically with the length of time the colloidal fluid remains on the disk surface. In addition to comparing longitudinal and perpendicular magnetic recording, a combination of spectral diffraction efficiency measurements, magnetometry, scanning electron microscopy and inductively coupled plasma atomic emmission spectroscopy of these gratings are employed to understand colloidal nanoparticle dynamics in this extreme gradient limit. Such experiments are necessary to optimize nanoparticle assembly and obtain uniform patterned features. This low-cost and sustainable approach to nanomanufacturing could enable low-cost, high-quality diffraction gratings as well as more complex polymer nanocomposite materials assembled with single-nanometer precision. [Preview Abstract] |
Tuesday, March 19, 2013 11:39AM - 11:51AM |
G32.00003: Self-assembly and Photo-patterning in Polymer-fullerene Nanocomposite Thin Films Him Cheng Wong, Anthony Higgins, Andrew Wildes, Jack Douglas, Joao Cabral We report the directed self assembly of fullerenes in polymer thin films. The fullerenes are found to assemble spontaneously into spinodally coordinated clusters upon thermal annealing. The process yields well-defined structures, ranging from sparse heterogeneous nucleation to dense spinodal-like morphologies with tuneable characteristic spatial frequency and amplitude which coarsen with time, following well-defined scaling laws [1]. Mapping of this self assembly process utilized both real and reciprocal space techniques: optical and scanning force microscopy and neutron reflectivity. With external fields: light exposure and substrate surface energy, we demonstrate further tuneability over nanocomposite thin film morphology and substantial improvement on ultrathin film stability. By modulating the external fields on nanocomposite film with photomask, followed by thermal annealing, the film morphology and stability can be directed into various patterns, including a prototype polymer-fullerene circuit [2]. These results provide insights into fullerene self assembly in polymers and underscore their photoactive nature, an effect of great interest in the performance and stability of organic photovoltaics (OPV). [1] Wong H C and Cabral J T 2010 Phys. Rev. Lett. 105 038301 and 2011 Macromolecules 44 4530. [2] Wong H C, Higgins A M, Wildes A, Douglas J F, Cabral J T 2012 Adv. Mater. In Press. [Preview Abstract] |
Tuesday, March 19, 2013 11:51AM - 12:03PM |
G32.00004: Co-assembly of Nanorods and Photosensitive Polymer Blends Ya Liu, Olga Kuksenok, Anna Balazs Using computational modeling, we establish means of controlling structure formation in nanocomposites comprising nanorods and a photosensitive binary blend. The complex cooperative interactions in the system include the preferential wetting between the rods and one of the phases in the blend, steric repulsion between the coated rods and the response of the binary blend to light. Namely, under uniform illumination, the binary mixture undergoes both phase separation and a reversible chemical reaction, leading to a morphology resembling that of a microphase-separated diblock copolymer. When a second, higher intensity light source is rastered over the sample, the binary blend and the nanorods co-assemble into regular, periodically ordered structures. In particular, the system displays an essentially defect-free lamellar morphology, with the nanorods localized in the energetically favorable domains. By varying the speed at which the secondary light is rastered over the sample, we can control the directional alignment of rods within the blend. Our approach provides an effective route for achieving morphological control of both the polymeric components and nanoparticles, providing an effective means of tailoring the properties and ultimate performance of the composites. [Preview Abstract] |
Tuesday, March 19, 2013 12:03PM - 12:15PM |
G32.00005: Anisotropic Thermal Processing of Polymer Nanocomposites via the Photothermal Effect of Gold Nanorods J.R. Bochinski, S. Maity, L.I. Clarke, K.A. Kozek, W. Wu, J.B. Tracy Embedding metal nanoparticles within polymeric materials enables spatially-selective, in-situ thermal polymer processing [1,2]. When irradiating such a nanocomposite with light resonant with the particle's surface plasmon resonance, the photothermal effect efficiently transforms the energy into localized heat. Utilizing anisotropically-shaped particles enables further heating control based on the polarization sensitivity of the light-particle interaction. Photothermal heating from oriented gold nanorods selectively heats polymeric nanofibers by melting fibers lying only along a chosen direction while leaving the remaining material largely unaffected [3]. Fluorescence-based temperature-sensing measurements confirms heating in selected fibers and its absence in counter-aligned fibers. Such facile thermal processing of a specified subset of a sample, while the remainder is unchanged cannot be achieved through conventional heating. Results on spatially-selective heating and nanoscale temperature measurements within polymer systems doped with active nanoparticles will be discussed.\\[4pt] [1] S. Maity et al., \textit{Polymer} \textbf{52}, 1674 (2011).\\[0pt] [2] S. Maity et al., \textit{Adv. Funct. Mat.} (in press) (2012).\\[0pt] [3] S. Maity et al., \textit{Part. \& Part. Syst. Char.} (in press) (2012). [Preview Abstract] |
Tuesday, March 19, 2013 12:15PM - 12:27PM |
G32.00006: Responsive and Hybrid Nanostructures through Self-Assembly of Polymeric Macroions, Inorganic Nanoclusters and Dyes Franziska Groehn, Jasmin Duering, Daniel Moldenhauer Recently we have introduced a novel type of self-assembled ``nano-objects'' in solution: From the association of macroions and multivalent counterions well-defined and stable structures in the shape of spheres, rod, rings, hollow spheres and networks can form in solution. Using light-addressable counterions, it is possible to switch the particle size through UV irradiation. Building blocks can be of organic or inorganic nature: Using gold or cadmium sulphide nanoclusters results in hybrid assemblies which also functionally combine nanoparticle and dye. Thermodynamic studies in combination with a detailed structural characterization yield insight into driving forces and structural control in the self-assembly process. Crucial is the delicate interplay of ionic, $\pi -\pi $, and Hamaker interaction. The concept is particularly attractive, as it relies on general physical effects - that is the combination of different non-covalent interactions - and hence is very versatile. Great potential of the structures presented lies in areas such as catalysis and energy conversion. [Preview Abstract] |
Tuesday, March 19, 2013 12:27PM - 12:39PM |
G32.00007: Utilizing Matrix-Filler Interactions in the Design of Stimuli-Responsive, Mechanically-Adaptive Electrospun Composites Nandula Wanasekara, David Stone, Gary Wnek, LaShanda Korley A new class of all-organic, stimuli-responsive and mechanically-adaptive electrospun nanocomposites, which have the ability to alter their stiffness upon hydration, were developed. These materials were fabricated by incorporating an electrospun mat of poly(vinyl alcohol) (PVA) as the filler in a polymeric matrix consisting of either poly(vinyl acetate) (PVAc) or ethylene oxide-epicholorohydrin copolymer (EO-EPI). The incorporation of high stiffness, high aspect ratio PVA filler mat significantly enhanced the tensile storage modulus of EO-EPI based composites, while modulus enhancement was only noticed above the glass transition for PVAc-based composites. Composite materials based on a rubbery EO-EPI host polymer and PVA filler exhibit an irreversible reduction by a factor of 12 of the tensile modulus upon hydration. In contrast, composites comprised of PVAc show a reversible reduction of modulus by a factor of 280 upon water uptake. The mechanical morphing of the electrospun composites is the result of the filler crystallinity, and matrix-filler interactions facilitated by the surface hydroxyl groups of the PVA filler. The choice of polymer matrix and electrospun nanofiber fillers allow control of matrix-filler interactions in a new series of all-organic composites to achieve desired stimuli-responsiveness and mechanical-adaptability upon exposure to various stimuli. [Preview Abstract] |
Tuesday, March 19, 2013 12:39PM - 12:51PM |
G32.00008: Structure and Transport Anomalies in Soft Colloids Samanvaya Srivastava, Lynden Archer We present structure, dynamics and rheology measurements for model nanoparticle suspensions comprising of silica nanoparticles, densely grafted with oligomeric polyethylene glycol (PEG) chains and suspended in similar PEG oligomers. Small angle X-ray scattering reveals anomalous structural trends wherein the particle-particle correlations are found to decrease as the particle volume fraction rises beyond the point of particle overlap. Upon further increase in the particle loading, investigation of the particle dynamics through X-ray photon correlation spectroscopy points towards an unusual speeding up of the nanoparticles. Analogous ``cascade of anomalies'' are observed in systems including complex molecular fluids like water and silica as well as in systems interacting via soft repulsive potentials, and similar forces are expected to lead to the origin of these anomalous trends in all the cases. [Preview Abstract] |
Tuesday, March 19, 2013 12:51PM - 1:03PM |
G32.00009: Simulations of Nanoparticle Ordering in Polymer Brush/Solvent Mixtures Gary S. Grest, Shengfeng Cheng, Mark J. Stevens Organizing nanoparticles into a desired super-structure is crucial for their technological applications. We present molecular dynamics simulations of the assembly of nanoparticles during the evaporation of solvent from 3-component mixtures of nanoparticles and solvent in contact with an end-grafted polymer brush. The organization of nanoparticles strongly depends on their interaction with polymer chains. For relatively weak attraction between the nanoparticles and brush, the nanoparticles straddle the brush surface and form an ordered lattice. For a strong attraction between the nanoparticles and polymer, the nanoparticles are engulfed inside the brush and the packing quality diminishes, because the lateral diffusion of the nanoparticles is suppressed. The opposite trend is observed in the case in which the polymer chains are not grafted to a substrate. In this case, a layer of nanoparticles is entrapped in the concentrated polymer film at the interface and assemble into a close-packed hexagonal lattice for strong mutual attraction, while for weak interactions the nanoparticles are mostly dispersed in the relatively solvent-rich solution below the interface and remain disordered. [Preview Abstract] |
Tuesday, March 19, 2013 1:03PM - 1:15PM |
G32.00010: Tailoring Surface Roughness by Grafting Nanoparticles to Random Copolymer Films Matthew Caporizzo, Rami Ezzibdeh, Russell Composto The effect of random copolymer composition on surface attachment and sinking of amine functionalized silica nanoparticles (d$=$45 nm) is investigated. Films of poly(styrene-ran-tert-butyl acrylate) (StBA) with 37{\%} tBA are converted to poly(S-ran-acrylic acid) (SAA) by annealing for 15h at temperatures ranging from 135C to 200C. The conversion of the tBA ranges from under 10{\%} to 100{\%} and is monitored by ellipsometry and ATR-FTIR. At complete conversion (25 wt{\%} AA), SAA forms nano-phase separated domains that result in particle aggregation within AA rich domains. At lower AA conversion, a disordered polymer morphology leads to grafting sites which are randomly distributed. NPs graft from nearly a complete monolayer to multilayers depending the percent of AA. Both the rate of NP attachment and the maximum loading of NPs into the film scale with the fraction of AA; this behavior is attributed to a reduction in the energetic barrier for the particle to sink into the film with increased swelling (more hydrophilic). A particularly attractive outcome of this systematic study is that optically transparent films with controlled roughness can be routinely prepared. Such films are of interest for investigating biomolecular adsorption and superhydrophobic, clear, non-fouling coatings. [Preview Abstract] |
Tuesday, March 19, 2013 1:15PM - 1:27PM |
G32.00011: Photothermally-induced rotation of gold nanorods within a polymer matrix to probe local nanocomposite properties Somsubhra Maity, Laura Clarke, Jason Bochinski The photothermal effect of gold nanorods embedded in polymer thin films produces localized heat depending upon the relative orientation of the rod and incident light field polarization. Simultaneous application of electric and light fields enables creation of thin films having aligned nanorods from those with initially randomly-oriented particles, as well as subsequent manipulation of rod orientation within the material environment. This is due to local melting of the polymer in the immediate vicinity of the particles which facilitates particle re-orientation. Conversely, solely under sufficient resonant light irradiation, initially aligned nanorods tend to randomize their orientation when the local environment melts. The rotational dynamics of the rods (i.e., alignment fidelity and rotation speed) depends on the polymer melt viscosity and thus directly reflects the local temperature around the rods which may vary significantly from the bulk temperature: conveniently, both rod orientation and bulk temperature can be simultaneously determined using optical methods. Thus, this combined approach provides both an in situ post-fabrication technique to manipulate alignment of rods and a tool to probe local temperature in polymer nanocomposites. [Preview Abstract] |
Tuesday, March 19, 2013 1:27PM - 2:03PM |
G32.00012: Polymer Nanocomposite Films: Dispersion of Polymer Grafted Nanorods and Optical Properties Invited Speaker: Russell Composto The thermodynamic factors that affect the dispersion of polymer-brush grafted gold nanorods (NR) in polymer matrix films have been studied by experiment and theory. When brush and matrix have a favorable interaction, such as poly(ethylene oxide) (PEO)-NR/ poly(methyl methacrylate) (PMMA) and polystyrene (PS)-NR / poly(2,6-dimethyl-p-phenylene oxide) (PPO), nanorods are uniformly dispersed. For PEO-NRs in PMMA, the NRs are regularly spaced and well dispersed, independent of the ratio of the degree of polymerization of the matrix (P) to that of the brush (N), namely P/N. As the NR volume fraction increases, the local orientation of the nanorods increases, whereas the macroscopic orientation remains isotropic. When the brush and matrix are similar (i.e., PS-NR / PS and PEO-NR / PEO), the nanorods randomly disperse for P/N \textless\ 2 (i.e., wet brush), but align side-by-side in aggregates for P/N \textgreater\ 2. UV-visible spectroscopy and discrete dipole approximation (DDA) calculations demonstrate that surface plasmon coupling leads to a blue shift in the longitudinal surface plasmon resonance (LSPR) as P/N increases. For P/N \textgreater\ 2, self-consistent field theory (SCFT) calculations and Monte Carlo (MC) simulations indicate that nanorod aggregation is caused by depletion-attraction forces. Starting with a dry brush system, namely, a PS matrix where P/N $=$ 30, these attractive forces can be mediated by adding a compatibilizing agent (e.g., PPO) that drives the NRs to disperse. Finally, dry and wet brush behavior is observed for NR aspect ratios varying from 2.5 to 7. However, compared at the same volume fraction, long rods for the dry case exhibit much better local order than lower aspect ratio nanorods, suggesting that long rods may exhibit nematic-like ordering at higher loadings. [Preview Abstract] |
Tuesday, March 19, 2013 2:03PM - 2:15PM |
G32.00013: Self-assembly of defect-free particle monolayers on flexible films Md.Shahadat Hossain, Bhavin Dalal, Sathishkumar Gurupatham, Ian Fischer, Pushpendra Singh, Nadine Aubry We have recently shown that the capillarity-based process for self-assembling particle monolayers on fluid-liquid interfaces can be improved by applying an electric field in the direction normal to the interface. The electric field gives rise to repulsive dipole-dipole forces amongst the particles causing them to move apart, and thus allowing them to move freely without blocking one another. The latter is important in the formation of virtually defect-free monolayers with long-range order. In this talk, we present a technique for freezing these expanded monolayers onto the surface of a flexible thin film. The technique involves assembling the monolayer on the interface between a UV-curable resin and a fluid which can be air or another liquid, and then curing the resin by applying UV light. The monolayer becomes embedded on the surface of the solidified resin film. [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