Bulletin of the American Physical Society
2006 APS March Meeting
Monday–Friday, March 13–17, 2006; Baltimore, MD
Session R24: Block Copolymer Applications |
Hide Abstracts |
Sponsoring Units: DPOLY Chair: Ting Xu, National Institute of Standards and Technology Room: Baltimore Convention Center 321 |
Wednesday, March 15, 2006 2:30PM - 2:42PM |
R24.00001: Catalysts from Block Copolymers David Durkee, Nitash Balsara, Alexis Bell Homogeneous catalysts are widely used to catalyze chemical reactions in the liquid phase; however, the separation of the reactants and products from such a catalyst can be difficult and often limits their use in practice. For this reason there has been considerable interest in the heterogenization of homogeneous catalysts. The use of polymers for this purpose has been particularly attractive because of the availability of a wide range of polymeric structures and methods for catalyst incorporation. Our novel approach for heterogenizing homogeneous catalysts that involves the use of microphase separated block copolymers. Block copolymers are synthesized from a crosslinkable monomer that forms a supporting gel upon crosslinking, an organometallic monomer that is catalytically active, and a depolymerizable block that can be removed to form mass transfer pathways, or pores. When placed in a solvent, the polymer gel swells to facilitate transport of the reactants to the active centers and the transport of products from these centers. This is functionally similar to the synthesis of mesoporous siliceous materials created by an amphiphilic, structure-directing agent. However, in this system, placement of the catalyst site is also controlled by self-assembly. [Preview Abstract] |
Wednesday, March 15, 2006 2:42PM - 2:54PM |
R24.00002: Thermally Crosslinkable Diblock Copolymer Templates Julie Leiston-Belanger, Thomas Russell, Eric Drockenmuller, Craig Hawker The ability to create robust nanoporous templates using polymeric thin films is important for such applications as nanofabrication and selective filtration. Thermally crosslinkable diblock copolymers based on benzocylcobutene chemistry were synthesized that could be used to this end. Poly[(styrene-stat-benzocyclobutene)-b-(D,L-lactic acid)] (PSBCB-b-PLA) was made using living free radical and ring-opening polymerization techniques. This diblock copolymer was shown to microphase separate into a cylindrical morphology that could be stabilized by heating. The minor PLA component was then removed using base to create a nanoporous crosslinked template that was 30 nm thick, with pores about 14 nm in diameter. These nanoporous templates resisted pore collapse when subjected to harsh thermal and solvent conditions. Since the base degradation of PLA produces hydroxyl groups along the pore walls, the ability to access these groups, in conjuction with the thermal and solvent resistance, opens a wide range of organic reaction possibilities. [Preview Abstract] |
Wednesday, March 15, 2006 2:54PM - 3:06PM |
R24.00003: Ordered Hexagonal Arrays of Holes with 40 nm Period by Shear Alignment of Diblock Copolymer Bilayers Jose Vedrine, Douglas Adamson, Richard Register, Thomas Pickthorn, Paul Chaikin An ordered hexagonal array of holes was fabricated by shear-aligning a molten bilayer film of a sphere-forming diblock copolymer in a nitrogen atmosphere. The block copolymer consisted of a polystyrene (PS) matrix and polyisoprene (PI) spheres, and was spin-coated onto a Si substrate prior to shearing. The top layer of microdomains in the bilayer was removed via a nonselective fluorine-based reactive ion etch (RIE). The PI spheres in the remaining bottom layer were then degraded with ozone to produce a PS mask with an ordered array of voids. The voids were transferred into the Si substrate by RIE, producing a dense array of holes approximately 20 nm wide and spaced 40 nm apart. This bilayer shearing procedure allows for the production of hole arrays with excellent long-range orientational order and few grain boundaries, which are unachievable by shearing a single-layer film. In addition, Au was evaporated onto the array, yielding a film of Au with regular perforations having a 40 nm period. [Preview Abstract] |
Wednesday, March 15, 2006 3:06PM - 3:18PM |
R24.00004: Reversible Nanostructures Assembled from Amphiphilic Block Copolymers Chen Xu, Xuefeng Fu, Michael Fryd, Bradford Wayland, Karen Winey, Russell Composto We present a novel route to assemble perpendicular cylinders by converting an asymmetric diblock copolymer from poly(styrene-b-tert butyl acrylate) (PS-b-PtBA) to poly(styrene-b-acrylic acid) (PS-b-PAA) using an auto-catalytic reaction. Upon exposing films of PS-b-PAA to water, PAA cylinders constrained by the continuous, glassy PS phase protrude 10 nm above the surface and swell laterally to form mushroom caps, rendering the entire surface hydrophilic. The swelling dynamics of the PAA mushrooms is captured by a two-stage mechanism, where domain growth is controlled by super case II diffusion of water into PAA followed by the slow relaxation of the PAA chains. Upon partial drying in air, the mushroom collapses as stretched hydrophilic chains relax, which results in nanometer depression in the center of each cap. The nanostructures revert to their initial dimensions and area fractions upon complete drying, demonstrating reversibility of swelling. This finding provides a new route to fabricate stimuli-responsive materials for sensors, microactuators, and microfluidic devices. [Preview Abstract] |
Wednesday, March 15, 2006 3:18PM - 3:30PM |
R24.00005: Patterned mesoporous media via 3-D replication in supercritical Carbon dioxide. Sivakumar Nagarajan, Thomas Russell, James Watkins, Joan Bosworth, Peter Busch, Detlef Smilgies, Christopher Ober Mesoporous metal oxide films having cylindrical channels oriented normal to the surface have generated intense interest due to their potential use as sensors, catalysts and detection devices. Further, the ability to pattern these mesostructured films makes it versatile to generate mesoporous materials with precisely controlled geometries and morphologies. Here we describe a novel route to mesoporous silica films with perpendicular nanochannels prepared by the 3-D replication of block copolymer templates in supercritical carbon dioxide. Templates comprised of poly(alpha-methyl styrene) cylinders oriented normal in the matrix of poly (hydroxy styrene) having trace amounts of acid catalyst was infused with solutions of silica precursor in sc CO$_{2}$ to selectively deposit silica within the matrix. Calcination yielded the porous silica arrays. The phase selective deposition was enabled by segregation of acid catalyst into hydrophilic matrix. Substitution of acid catalyst with photo sensitive acid generators facilitates to pattern the mesoporous films, which could potentially have applications in microfluidic devices and low-dielectric constant layers for microelectronic devices. [Preview Abstract] |
Wednesday, March 15, 2006 3:30PM - 3:42PM |
R24.00006: Ordered Nanostructured Carbon Generated from Pyrolyzed Polymer Precursors inside Anodic Aluminum Oxide Template Jiun-Tai Chen, Kyusoon Shin, Julie Leiston-Belanger, Mingfu Zhang, Thomas Russell Various carbon structures were generated by using polystyrene-block-polyacrylonitrile (PS-b-PAN) as carbon precursors in the nanopores of anodic aluminum oxide (AAO) membranes. PS-b-PAN block copolymers were drawn into nanopores of AAO by capillary force. By using different annealing temperatures, block copolymer nanotubes or nanorods can be generated. The morphologies of PS-b-PAN inside the nanopores were induced by structural frustration and interfacial interactions and were investigated by transmission electron microscopy. After stabilization and pyrolysis of the carbon precursors, the morphologies were retained and various carbon structures can be obtained. The carbon structures were found to be amorphous by Raman spectroscopy and x-ray diffraction. [Preview Abstract] |
Wednesday, March 15, 2006 3:42PM - 3:54PM |
R24.00007: Soft molding to align cylindrical nanodomains of block copolymers Hideaki Yokoyama, Lei Li Block copolymers are a class of materials that self-assemble into ordered periodic nanostructures. However, we often find that such spontaneous self-assembly ends up with disappointing randomly oriented polygrain structures, which limit the application of the nanodomains. Soft molding is a unique technique to transfer topological pattern with a soft mold, which permits a conformal contact with surfaces. A soft mold with a periodic topological pattern is embossed on the block copolymer thin films. The soft molding not only replicates the topological pattern to the block copolymer thin films but also induces microscopic flow in block copolymer thin films and controls the orientation of cylindrical domains. We fabricated a single layer of 3 $\times$ 10$^5$ parallel cylindrical nanodomains over an area of 1 cm $\times$ 1 cm. [Preview Abstract] |
Wednesday, March 15, 2006 3:54PM - 4:06PM |
R24.00008: Nanopatterning of Viruses and Proteins Using Microphase Separated Block Copolymers Arthur Cresce, Angela Lewandowski, William Bentley, Peter Kofinas Diblock copolymers containing nickel ions have been prepared that are capable of selectively adsorbing histidine-tagged green fluorescent protein (hisGFP), and also binding tobacco mosaic virus (TMV). A block copolymer of norbornene and norbornene dicarboxylic acid was synthesized using ring-opening metathesis polymerization. A 400/50 block ratio achieved a spherical microphase-separated morphology with roughly 20 nm diameter dicarboxylic acid spheres. The spherical phase was exposed to nickel ions in solution, templating the formation of nickel nanoparticles. This process gave a nickel-loaded diblock copolymer film whose surface was used to chelate hisGFP. Fluorescence spectroscopy and TEM confirmed the presence of the protein on the polymer surface. A sulfonated triblock copolymer was loaded with nickel ions using a similar solution-doping procedure. The morphology of this copolymer was lamellar, and its sulfonated block was loaded with nickel ions. TEM studies revealed the presence of the virus on the surface of the copolymer and showed that the bond between the TMV and the polymer surface can withstand severe detergent washes. [Preview Abstract] |
Wednesday, March 15, 2006 4:06PM - 4:18PM |
R24.00009: Surface Directed Assembly of Viral Monolayers S. Wargacki, R. Naik, D. Phillips, M. Francis, V. Ward, E. Thomas, R.A. Vaia The facile two-dimensional fabrication of micron-scale patterns of ordered-nanoscale structures on flexible substrates has numerous broad implications, including sacrificial templates for further assembly, deposition or material removal. Previous examinations of block-copolymer assembly on micron-scale patterns with topological and/or chemical relief have demonstrated the ability to not only dictate the larger superstructure of the surface but also to impact the local nano-scale self-assembly and defect stability via confinement. These processes are examined with respect to the surface directed assembly of colloidal particles, specifically rod-like Tobacco Mosaic Virus (TMV) and iscohoderhal viruses \textit{Wiseana} Iridovirus (WIV) and MS2. The unique surface chemistry and shapes provide a complement to traditional colloidal building-blocks. Initially, high throughput processing by convective self assembly (CSA) with orthogonal temperature gradients is combined with chemical modification of Silicon surfaces via soft-lithography to determine the key processing parameters for monolayer assembly. The impact of the viral shape (rod v. iscohodra) as well as the critical range of enthalpic interactions between the virus and substrate that control in-plane order and pattern formation will be discussed. [Preview Abstract] |
Wednesday, March 15, 2006 4:18PM - 4:30PM |
R24.00010: Guided Molecular Self-Assembly of Block Copolymer and Nanoparticles Shan Zou, Gilbert Walker Block copolymers form a variety of ordered structures on nanometer length scales, allowing them to serve as an ordered matrix for nanoparticles which add functionality to the composite. The result is an ordered array of nanoparticles with potential applications including magnetic storage media, photonic crystals, or high-surface-area catalysts. Here we demonstrate the molecular self-assembly of diblock copolymers and cadmium selenide based nanoparticles. In thin films, nanoparticles assemble into one of the ordered pattern domains formed by the diblock copolymers on Si substrates. Ideas for directing the individual particles to different locations normal to the surface will be discussed. [Preview Abstract] |
Wednesday, March 15, 2006 4:30PM - 4:42PM |
R24.00011: Effect of Casting Solvent on the Morphology of Block Copolymer / Maghemite Nanoparticle Mixtures Kookheon Char, Moon Jeong Park We investigate the effect of casting solvent on the morphology of block copolymer / magnetic nanoparticle (NP) mixtures. Monodisperse maghemite NPs with surfaces modified with oleic acids have been synthesized and PS-b-PI, PS-b-PB, PS-b-PEO, and PS-b-P4VP, diblock copolymers showing cylindrical morphology were used as structure-directing matrices for the NPs. Four different solvents, hexane, toluene, THF, and CHCl3 were used to prepare film specimens by static casting and the interaction between mesophase-forming copolymers and nanoparticles, which can be tuned by casting solvent, leads to remarkably different hybrid morphology. With casting with good solvent for both blocks, with the increase in NP concentration, domains of NP aggregates were observed while the NPs were selectively incorporated into the minor domains of block copolymer under selective solvent condition. The interplay between magnetic NPs and block copolymers was also tested with different size of magnetic NPs and also with different molecular weight of block copolymers. In order to characterize the structural change of block copolymers associated with different NP loadings small- angle x-ray scattering was performed and the structural information is in good agreement with transmission electron microscopy images and differential scanning calorimetry results. [Preview Abstract] |
Wednesday, March 15, 2006 4:42PM - 4:54PM |
R24.00012: 2-D Hierarchical Structure of Block Copolymer / Bio-nanoparticle Complexes Dongseok Shin, Thomas Russell The morphology of complexes made of poly(styrene-b-N-methyl-4- vinylpyridinium iodide) (PS-P4VP•MeI) and horse spleen ferritin was investigated. A polymer film was casted on a substrate then was immersed in a protein solution to allow for protein adsorption. After rinsing the sample with deionized water and drying, the specimen was placed in a mixed vapor of benzene and water. This solvent annealing technique has allowed us to get the final morphology of the complex at ambient condition. At low loading of ferritin, the morphology of the block copolymer was conserved and the ferritin was localized at the microdomains of the minor component (P4VP•MeI). As the loading of ferritin increased, the microdomains containing ferritin particles grew in size and elongated in shape. Eventually, the micordomains occupied by ferritin were connected and formed closed loops at high loading of ferritin. However, in the area enclosed with the loops, the morphology of the block copolymer itself was maintained. As a result, we were able to get a hierarchical structure by incorporating bio-nanoparticles into block copolymer thin films. [Preview Abstract] |
Wednesday, March 15, 2006 4:54PM - 5:06PM |
R24.00013: Effect of Interacting Nanoparticles on the Ordered Morphology of Block Copolymer / Nanoparticle Mixtures Moon Jeong Park, Yu Jin Kang, Kookheon Char We investigate the effect of hard additives, i.e., magnetic nanoparticles (NPs), on the ordered morphology of block copolymers by varying NP concentration. In order to characterize the structural change of block copolymer associated with different NP loadings, small-angle x-ray scattering and transmission electron microscopy were performed. Monodisperse maghemite NPs with surfaces modified with oleic acids have been synthesized and PS-b-PI diblock copolymers showing cylindrical morphology were used as structure-directing matrices for the NPs. With the increase in NP concentration, domains of NP aggregates were observed. It is surprising to note that regular lattice-like aggregates with maghemite NPs induce an intriguing morphological transformation from the hexagonal cylinders to the body-centered cubic spheres via undulated cylinders of block copolymers, which does not show such order-order transition without NPs. The interplay between magnetic NPs and block copolymers was also tested with different size of magnetic NPs and also with different molecular weight of PS-b-PIs. We also demonstrate the preferred orientation of anisotropic microdomains of PS-b-PI, which is known to be difficult to orient by applying electric or magnetic field. This result could add more flexibility in structural control and orientation of block templates opening up new applications in the future. [Preview Abstract] |
Wednesday, March 15, 2006 5:06PM - 5:18PM |
R24.00014: Magnetic Properties of Ni Nanoparticles Dispersed in Polystyrene-Isoprene-Polystyrene Triblockcopolymers Mircea Chipara, You Qiang, Linfeng Guo, Aminian Hossein, Jeffrey M. Zaleski, Sy-Hwang Liou Polymer based magnetic nanocomposites were obtained by dispersing Ni nanoparticles within polystyrene-isoprene-polystyrene block copolymers. High power sonication (500 W) was used to obtain an uniform dispersion of magnetic nanoparticles. The dependence of the magnetic properties of these nancomposite materials as a function of Ni concentration (from 0 {\%} Ni to about 25 {\%} Ni) and temperature (in the range 100 K to 500 K) was analyzed. The agglomeration of Ni nanoparticles above the glass transition of the hard phase was observed. The process is irreversible. The agglomeration of nanoparticles is triggered by the fast decrease of diffusion coefficients above the glass transition temperature of the hard phase. Such large changes of magnetic properties triggered by the elastic properties of the matrix were not yet been reported. Ferromagnetic resonance data on Ni based composites in the temperature range 100 to 500 K confirmed the agglomeration of Ni nanoparticles and supported the irreversible character of this modification. Additional magnetic data were obtained by SQUID, VSM, and AFM (with magnetic tips). [Preview Abstract] |
Wednesday, March 15, 2006 5:18PM - 5:30PM |
R24.00015: Penetrant Diffusion in a SEBS Triblock Copolymer by Pulse Field Gradient NMR Alan Jones, Marcus Giotto, Alana Canfield, Guoxing Lin Solid triblock copolymers can serve as the basis for membranes in such applications as separations and fuel cells. Diffusion of a low molecular weight penetrant in such a membrane is strongly affected by the morphology. The effect of the morphology on the translational motion of the penetrant can be directly assessed by pulse field gradient NMR measurements. The rotational and translational motion of 2,2,4-trimethylpentane (TMP) in a SEBS triblock will be characterized by NMR. TMP is primarily soluble in the rubbery EB phase of the SEBS triblock so that this phase then acts as the conductive component of the membrane. [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