Bulletin of the American Physical Society
2005 APS March Meeting
Monday–Friday, March 21–25, 2005; Los Angeles, CA
Session L30: Polymers-Inorganic Composites I |
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Sponsoring Units: DPOLY Chair: Dilip Gersappe, SUNY Stony Brook Room: LACC 505 |
Tuesday, March 22, 2005 2:30PM - 2:42PM |
L30.00001: Selective Metallization of Block Copolymers Using Supercritical Carbon Dioxide James Sievert, Thomas Russell, James Watkins In this research phase-separated structures of styrene-vinylpyridine block copolymers are used as templates for macromolecule-metal nanocomposites. Under optimal conditions, templates are prepared as thin films or in bulk and metallized without disturbing the ordered structure. We have developed a procedure that deposits metal within the polymer using supercritical carbon dioxide-soluble metal precursors. The use of supercritical carbon dioxide allows for selective metallization of the polymer at or below the glass transition, without disrupting the morphology. In addition, similar procedures have been investigated using metal salts and acids. Using these techniques, metals and metal-sulfides including silver, gold, platinum and zinc sulfide have been deposited. [Preview Abstract] |
Tuesday, March 22, 2005 2:42PM - 2:54PM |
L30.00002: Holographically phase separated gold/nanoparticle films Kashma Rai, Adam Fontecchio Holographic Polymer Dispersed Liquid Crystals (HPDLCs) show a shift in the reflected wavelength due to a change in the fringe separation of the Bragg gratings when pressure is applied perpendicular to the surface plane. Typically urethane based monomer forms the polymer layer via photopolymerisation by holographic laser exposure in conjunction with liquid crystals. In this paper we study the effect of step variation in pressure in the range of 0-20psi on the peak wavelength reflection of the holographic polymer dispersed gold nanoparticles. The high refractive index mismatches between gold and polymer composition produces good quality Bragg diffraction gratings. We investigate the use of Polydimethylsiloxane (PDMS), a siloxane based oligomer with high elasticity as the polymer for the gold/ polymer grating formation. The high elasticity of the PDMS along with sensitivity of the film to applied pressure enhances the pressure response. We present the application of the polymer /gold nanoparticle films for pressure sensors, in which a linear change in the wavelength of the reflected light corresponds to the pressure variations on the films. [Preview Abstract] |
Tuesday, March 22, 2005 2:54PM - 3:06PM |
L30.00003: Controlling Self-Assembly of Gold Nanoparticles in Block Copolymer Templates Bumjoon Kim, Julia J. Chiu, David J. Pine, Edward J. Kramer Self assembly of inorganic nanoparticles within a block copolymer offers a way to produce materials with unique optical, electronic and magnetic properties. To reveal some of the fundamentals of the self assembly we have investigated the system consisting of symmetric polystyrene-poly(2-vinylpyridine) (PS-P2VP) whose total molecular weight (M$_{n})$ is 197 kg/mol and polymer-coated gold nanoparticles. Gold nanoparticles are stabilized by carrying out their synthesis in mixtures of thiol terminated PS (PS-SH) and P2VP (P2VP-SH) chains whose M$_{n}$ is 1.3 kg/mol. The surface of these particles is tailored by changing the ratio of PS-SH to P2VP-SH on their surface. While PS coated gold nanoparticles are observed to locate near the center of PS domain, gold nanoparticles coated with a 1:1 mol ratio of PS-SH to P2VP-SH are segregated at the intermaterial dividing surface (IMDS) of PS-P2VP. The particle location (the center of PS domain, the IMDS of PS-P2VP chains, the center of P2VP domain) depends on the ratio of PS to P2VP on the gold surface. The range of ratios of the PS to P2VP where gold particles segregate to the IMDS is extremely broad, raising interesting questions about the spatial distribution of PS and P2VP on the gold surface. [Preview Abstract] |
Tuesday, March 22, 2005 3:06PM - 3:18PM |
L30.00004: Synthesis of Ordered Fe$_{2}$O$_{3}$ Nanoparticles within Norbornene Methanol/Norbornene Dicarboxylic Acid Diblock Copolymers Pinar Akcora, Peter Kofinas, Robert Briber Norbornene methanol-deuterated norbornene dicarboxylic acid diblock copolymers were synthesized by ring-opening metathesis polymerization. Iron oxide nanoparticles were formed in the microdomains of the diblock through a solution doping mechanism. Polymer samples with and without iron oxide particles were solution cast under a solvent saturated atmosphere. The morphology of the diblock copolymer and the dispersion of iron oxide nanoparticles within the copolymer were examined with transmission electron microscopy and the two morphologies were compared. Spherical iron oxide particles of 3-5 nm in size showed ferrimagnetic behavior at 5 K with high magnetization values (40 emu/g polymer or 1300 emu/cm$^{3})$ at 5 Tesla. It was shown that the magnetic properties and morphology of the iron oxide nanoparticles can be tailored by the in-situ synthesis within the domains of the copolymer. By controlling the size and dispersion of the Fe$_{2}$O$_{3}$ naoparticles, the magnetization moments were found to be higher than that of magnetic particles in other polymer systems. [Preview Abstract] |
Tuesday, March 22, 2005 3:18PM - 3:30PM |
L30.00005: Microphase Segregation in Organic-Inorganic Randomly Grafted Copolymers Engin Burgaz , Lei Zheng, Gregoire Cardoen, E. Bryan Coughlin, Samuel P. Gido We have studied the microphase ordering of Polybutadiene-Polyhedral Oligomeric Silsesquioxane (PBD-POSS) randomly grafted copolymers using High Temperature Small Angle X-Ray Scattering and TEM. The polybutadiene forms the backbone of these copolymers whereas POSS cubic nanoparticles are grafted randomly along the backbone. In the bulk morphology, these molecules self-assemble due to the aggregation of the POSS nanoparticles and form randomly orientated two-dimensional lamellar sheets of POSS in the polybutadiene matrix. Our results show that the wave vector of the lamellar phase formed by these randomly grafted copolymers, has a temperature dependence different from either linear random copolymers or block copolymers. Our results are in consistent with the recently established randomly grafted copolymer mean-field theory and experiments. [Preview Abstract] |
Tuesday, March 22, 2005 3:30PM - 3:42PM |
L30.00006: Electrospun Fibers from Self-assembling Polystrene-b-Polyisoprene Block Copolymers Yong Lak Joo, Timur Ivannikov, Jeanne Panels, Prashant Kakad, Ulrich Wiesner, Manuel Marquez Formation of submicron scale fibers with various domain shapes via electrospinning poly(styrene-\textit{block}-isoprene) (PS-$b$-PI) has been investigated. Monodisperse PS-$b$-PI block copolymers with a range of compositions were synthesized using anionic polymerization and were dissolved in THF. Solutions of 10 to 40 wt{\%} of PS-$b$-PI in THF were electrospun, and fibers with average diameters from 100 nm to 5 $\mu $m were obtained. Transmission electron micrographs taken from a microtomed thin electrospun fiber of a PS-$b$-PI block copolymer show PI cylinders aligned along the fiber axis, whereas TEM images of thicker electrospun fibers reveal that the skin and core regions can exhibit different domain structures. This skin-core differentiation in the fiber is possibly due to concentration gradient during solvent evaporation and short residence time involved in the electrospinning process. The TEM and SAXS studies show more uniform domain structures in the fibers after the removal of the residual solvent. [Preview Abstract] |
Tuesday, March 22, 2005 3:42PM - 3:54PM |
L30.00007: Nanometer scale patterning using di-block copolymer Zuoming Zhao, Tae-Sik Yoon, Wen Feng, Biyun Li, Ya-Hong Xie Di-block copolymer thin films of PS-PI, PS-PB and PS-PMMA are investigated on Si substrates. The morphology evolution with polymer thickness is studied using optical microscopy. As-coated polymer exhibits a very smooth surface. After annealing polymer over glass-transition temperature, the polymer exhibits a smooth surface only at certain thickness L$_{0}$. Transmission electron microscopy is used to study the microphase separation in polymer at different stages. Clear phase separation is observed in the polymer after staining with osmium tetraoxide (OsO$_{4})$. Long time annealing increases the long-range ordering. After treatment with ozone, disappearance of dark dots due to staining of Os and appearance of white hole indicate that the polymer with double-bond is removed from copolymer film. Scanning electron microscopy shows that polymer films after reactive ion etching give a regular hole pattern which can serve as mask for nanometer scale patterning. [Preview Abstract] |
Tuesday, March 22, 2005 3:54PM - 4:06PM |
L30.00008: Nanofibers And Related Structures Formed By Polymerization S. V. Doiphode, D. H. Reneker Nanofibers of cyanoacrylate were obtained by polymerization from the monomer vapor at a temperature near room temperature. The nanofibers had diameters ranging from 20 nm to 100 nm and lengths of up to several millimeters. Water molecules present on the substrate initiated the living anionic polymerization. As growth continued, the living ends were carried on the tip of each growing nanofiber. These nanofibers formed on glass, metal, plastic, electrospun nanofibers of other polymers, and other surfaces. Some fibers were tapered, some were branched, and some were bent. The number of fibers was varied by controlling the exposure of the substrate to water vapor. Under different conditions the monomer vapor was collected as droplets along electrospun nanofibers, or as droplets at the points where two electrospun nanofibers crossed. The addition of the initiator caused the droplets to polymerize, forming permanent beads on the fibers, and strong mechanical connections at the cross points. This phenomenon provides new ways to construct nanofiber structures engineered on nanometer scales. For example, filters constructed from an open structure of fibers can be coated with nanofibers polymerized from a vapor of nanometer scale droplets flowing through the structure, to improve the capture of molecules or particles. [Preview Abstract] |
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