Bulletin of the American Physical Society
2008 APS March Meeting
Volume 53, Number 2
Monday–Friday, March 10–14, 2008; New Orleans, Louisiana
Session Q22: Focus Session: New Methods in Polymer Physics |
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Sponsoring Units: DPOLY Chair: Carson Meredith, Georgia Institute of Technology Room: Morial Convention Center 214 |
Wednesday, March 12, 2008 11:15AM - 11:51AM |
Q22.00001: Combinatorial Methods for Polymer Physics: Tools for discovery that enable knowledge generation Invited Speaker: There is no doubt that the advent of combinatorial and high-throughput experimental methods has revolutionized industrial materials discovery by accelerating the research and development of a huge variety of materials systems and devices. This is because ``combi'' techniques enable researchers to approach large, complex variable spaces in a more rapid, thorough and rational manner. Accordingly, these methods hold great potential for polymer physicists who are increasingly faced with more intricate molecular architectures, more complicated properties interrelations, and more convoluted behaviors from the systems they consider. As demonstrated in recent years, when combi tools are directed towards ``knowledge generation'' and complex materials science problems, academic researchers can reap the benefits that industrial practitioners of these techniques have seen in discovery and engineering. In this talk we will discuss some key combi and high-throughput tools for polymer research, and demonstrate how they can be applied to key problems in polymers physics. Topic areas will include thin film polymer stability and wetting, block copolymer morphology and phase behavior, polymer surfaces and interfaces, and the structure and behavior of polymer solutions. [Preview Abstract] |
Wednesday, March 12, 2008 11:51AM - 12:03PM |
Q22.00002: In-situ Liquid Accessible Volume Measurement of Polymer Films Using Surface Plasmon Resonance Yibing Zhang, Mohsen Yeganeh Many physical properties of a polymer in contact with liquid can be markedly affected by the amount of the liquid that can penetrate into the polymer matrix. The liquid accessible volume in a polymer matrix is difficult to determine at elevated temperatures and not possible with simple weight gain measurements. A high sensitivity optical Surface Plasmon Resonance (SPR) technique, which has been widely used in chemical and biomedical applications, was developed for determination of liquid accessible volume in a polymer matrix at both room and high temperatures (up to 150 $^{o}$C). Experimental results and theoretical calculation are in excellent agreement. Hysteresis in liquid accessible volume as a function of organic liquid was observed when temperatures were cycled between room and high temperatures. The newly developed SPR technique for accessible volume determination has a great potential for \textit{in-situ} characterization of a polymer matrix in contact with liquid. [Preview Abstract] |
Wednesday, March 12, 2008 12:03PM - 12:15PM |
Q22.00003: Interface and dynamic indentation of crosslinked polyester films Suresh Ahuja The nanoindentation technique has drawn much interest recently for both its efficiency and versatility in measuring the mechanical properties of small volumes of materials and thin films. Since the unloading curve of polymers depends not only on the holding time but also on the unloading rate Hysitron Nanoindenter was used in our investigation of contact deformation of surfaces of polyester and polycarbonate supported on an aluminum substrate. Crosslinked polyesters with different gel concentration were produced on aluminum surfaces. Inter-phase plays a crucial role in composites. Stiffening and strengthening rely on load transfer across the interface, toughness is influenced by crack deflection/fiber pull-out, and ductility is affected by relaxation of peak stresses near the interface. Instead of strain softening with indentation depth observed in linear polymers, cross-linked polymers showed strain hardening. The extent of diffusion determines the extent of the interfacial region with the conformation loss of large molecules being higher than that of small molecules. Besides, considering the strain-hardening.an increasing stress is required to produce further plastic deformation after the material is strained beyond the yielding point, it is possible to separate the plastic deformation and the visco-elastic deformation and study them individually. Steady state deformation is compared with sinusoidal deformation relatable to differences in Tg from confinement effects. In cross-linked polymers, surface deformation is analyzed a three-layer model consisting of free surface layer, intermediate layer, and interface layer. Molecular relaxation dependence on molecular weight and cross-link density is shown. [Preview Abstract] |
Wednesday, March 12, 2008 12:15PM - 12:27PM |
Q22.00004: Prediction of Zeolite Types Based on Structural Data. M. Lach-hab, D.A. Carr, I. Vaisman, E. Blaisten-Barojas Application of knowledge discovery methods in the search of information contained in databases is an emerging field in materials science that plays an important role on facilitating data analysis. In this study we propose a model for identification of the zeolite mineral type based on the topological analysis of the underlying crystal structure. High-throughput generation of topological descriptors is derived from the Delaunay tessellation of zeolite supercells. Based on these descriptors, our Zeolite-Structure-Predictor is trained for classifying zeolite crystals into twenty two different types of minerals and is based on a random forest model constructed with attributes that include tetrahedrality index, in-sphere volume, average edge, frequency of occurrence and probability of oxygen rich selected simplices. The underlying crystal structure data used for this study are included in the Inorganic Crystal Structural Database (ICSD). [Preview Abstract] |
Wednesday, March 12, 2008 12:27PM - 12:39PM |
Q22.00005: Adaptable Polymer Microsrolls Kyriaki Kalaitzidou, Alfred J. Crosby Adaptable polymer particles that can change geometry, flow characteristics, and adsorption properties upon the stimulation of an environmental change, such as temperature are fabricated by utilizing the residual stress developed at the interface of a bilayer. We propose a phase diagram that can be used to predict the shape and the size of the adaptive polymer particles as a function of the materials modulus, thickness ratio and the bilayer's lateral dimensions. The method is applicable to any material combination that satisfies the design equations. The materials used in this work are gold/titanium (Au/Ti) and polydimethylsiloxane (PDMS). Initial demonstrations of this responsive control and its impact on properties of the adaptive polymer particles are also presented. These structures combined with their demonstrated reversibility have potential as capsules in drug delivery systems and novel conductive composites. [Preview Abstract] |
Wednesday, March 12, 2008 12:39PM - 12:51PM |
Q22.00006: Resonant soft x-ray GISAXS on block copolymer films Cheng Wang, T. Araki, B. Watts, H. Ade, A. Hexemer, S. Park, T.P. Russell, W.F. Schlotter, G.E. Stein, C. Tang, E.J. Kramer Ordered block copolymer thin films may have important applications in modern device fabrication. Current characterization methods such as conventional GISAXS have fixed electron density contrast that can be overwhelmed by surface scattering. However, soft x-rays have longer wavelength, energy dependent contrast and tunable penetration, making resonant GISAXS a very promising tool for probing nanostructured polymer thin films. Our preliminary investigation was performed using PS-b-P2VP block copolymer films on beam-line 5-2 SSRL, and beam-line 6.3.2 at ALS, LBNL. The contrast/sensitivity of the scattering pattern varies significantly with photon energy close to the C K-edge ($\sim $290 eV). Also, higher order peaks are readily observed, indicating hexagonal packing structure in the sample. Comparing to the hard x-ray GISAXS data of the same system, it is clear that resonant GISAXS has richer data and better resolution. Beyond the results on the A-B diblock copolymers, results on ABC block copolymers are especially interesting. [Preview Abstract] |
Wednesday, March 12, 2008 12:51PM - 1:03PM |
Q22.00007: Orientation Distribution for Thin Film Block Copolymers Ronald Jones, Xiaohua Zhang, Sangcheol Kim, Alamgir Karim, Robert Briber, Ho-cheol Kim The directed self-assembly of nanostructured films with vertically oriented morphologies is a potential solution for manufacture of next generation data storage platforms, microelectronic devices, and nanoporous membranes. In many of these applications, the distribution of orientation must be tightly controlled to enable pattern transfer. This parameter is expected to depend on factors such as the Flory-Huggins chi parameter, but little data has been reported to date. We present results from tomographic small angle scattering on a series of block copolymer films whose assembly has been directed through solvent annealing. Films of poly(styrene-b-ethylene oxide) are cast as a function of annealing time and their orientation distribution reported. The results provide significant insight into the fundamental limits of line edge roughness and defect control possible using this fabrication technique. [Preview Abstract] |
Wednesday, March 12, 2008 1:03PM - 1:15PM |
Q22.00008: Unusual Domain Morphology in PS-b-PFS Block Copolymer Films Seth Darling, Muruganathan Ramanathan, Elizabeth Nettleton Gaining control over the structure and order of self-assembled domains is critical to the success of bottom-up fabrication methodologies. We focus on the self-assembly of polystyrene-block-poly(ferrocenyldimethylsilane) block copolymers (PS-b-PFS). Thin films microphase separate to form nanoscale PFS cylinders within a PS matrix. Traditionally, order in such films is improved using thermal annealing, which has drawbacks including time requirements and possible thermal degradation. In this work, solvent annealing has been used, sometimes in concert with thermal annealing, to gain control over the microphase domain orientation. In addition to orientational control, novel domain morphologies have been observed. Thermochemical techniques and AFM and TEM imaging have been utilized to characterize these materials. Because of the comparatively high etch resistivity of the PFS block, this block copolymer holds potential in lithographic patterning of nanowires, nanopillar arrays, and nanofluidic channels. Some initial patterning results will also be presented. [Preview Abstract] |
Wednesday, March 12, 2008 1:15PM - 1:27PM |
Q22.00009: Using Functional Small Molecules to Control Self-Assembly and Patterning in Block Copolymer Thin Films C. Geraldine Bazuin, David Gaspard, Ximin Chen, Damien Mauran, Robert E. Prud'homme, Christian Pellerin Self-assembled thin films of block copolymers constitute an elegant means to obtain nanopatterns and nanotemplates on surfaces. Here, we demonstrate how interacting small molecules can be used to control the morphology of dip-coated block copolymer films. Such films obtained from THF solutions of styrene-4-vinylpyridine block copolymers (PS-b-PVP, ca. 29 wt percent VP) and naphthol (NOH), which hydrogen bonds to PVP, yield nanopatterns of quasi-hexagonally ordered nodules of PVP+NOH in a PS matrix. Washing in methanol removes the small molecules, leaving functional P4VP-lined nanopores in the film. These nanopores are receptor sites for molecules with desired properties. In contrast, naphthoic acid (NCOOH), which differs from NOH only by the hydrogen-bonding group, leads to fingerprint morphology under the same initial dip-coating conditions. By changing the conditions, in particular reducing the dip-coating speed sufficiently, the fingerprint morphology can be converted to quasi-hexagonal. Reflection-absorption infrared spectroscopy indicates that the proportion of small molecule incorporated into the dip-coated film is about half that found in solution for both NOH and NCOOH. [Preview Abstract] |
Wednesday, March 12, 2008 1:27PM - 1:39PM |
Q22.00010: Combinatorial Studies of Free Surface Effects on Block Copolymer Thin Films Thomas Epps, Julie Lawson, Thomas Scherr, Michael Fasolka To employ block copolymers for many nanoscale templating applications, it is essential to understand how the interfacial interactions originating from the substrate and free surface in ultrathin ($\sim $nm) films affect block copolymer morphologies. In this work, we manipulated the free surface interactions of poly(styrene-b-isoprene-b-styrene) and poly(styrene-b-ethylene oxide) thin films using solvent vapor gradient libraries. These libraries were created using fluorinated acrylate microfluidic devices consisting of a two-input solvent vapor mixing tree and several discrete solvent vapor flow channels. Areas of the thin films exposed to vapor flowing through the channels were subsequently examined by AFM. Analysis along the discrete vapor gradients showed the expected results for the channels at the extremities (representing the approximately single component vapor streams); however, the channels at intermediate vapor compositions show time-dependent nanostructure behavior that was a function of both vapor composition and distance along the channel. [Preview Abstract] |
Wednesday, March 12, 2008 1:39PM - 1:51PM |
Q22.00011: Self-assembly of Cylindrically Confined Block Copolymers in Core-Shell Electrospun Fibers Minglin Ma, Gregory Rutledge We report the development of electrospun fibers with internal structure by two-fluid coaxial electrospinning of block copolymers. Microphase separated morphologies with a long-range order were obtained by annealing the fibers at a temperature greater than the glass transition temperature of either block of the copolymer core but less than the glass transition temperature of the polymer shell. Various interesting, unusual and in some cases unprecedented self-assembled morphologies of block copolymers have been observed. Based on quantitative analyses, confinement within the cylindrical geometry was found to affect both the microphase morphology and fundamental period of the block copolymer. These internally nanostructured fibers have both practical and fundamental intellectual importance. For example, these fibers have unique potential for applications in optics, photonics, drug delivery, and other uses because of their small diameter, unique internal structure, and continuous filamentary nature. [Preview Abstract] |
Wednesday, March 12, 2008 1:51PM - 2:03PM |
Q22.00012: A Generalized Method for the Preparation of Neutral Brushes from Homopolymer Mixtures Shengxiang Ji, Guoliang Liu, Fan Zheng, Franz Himpsel, Paul Nealey We demonstrate a new, generalized approach for the formation of neutral surfaces that uses a ternary blend of hydroxyl-terminated homopolymers A-OH and B-OH and a low MW A-$b$-B block copolymer. The presence of the block copolymer effectively homogenizes the A/B homopolymer mixture before the homopolymers are grafted onto the substrate, thereby preventing macroscopic phase separation of the homopolymer mixture, and maintaining chemical neutrality over the length scales necessary for the self-assembly of block copolymer microdomains. The grafting ratios of the two homopolymers were varied simply by changing the blend ratios. Neutral compositions for P(S$-b-$MMA) and P(S-$b$-2VP) were located using this binary homopolymer mixture strategy. [Preview Abstract] |
Wednesday, March 12, 2008 2:03PM - 2:15PM |
Q22.00013: Centrifugal adhesion balance (CAB) : A novel surface characterization technique Rafael Tadmor, Lan Dang, Aisha Leh, Prashant Bahadur, Kumud Chaurasia Drop lateral adhesion to a surface and the condition for drop sliding along a surface are key issues in many disciplines including biophysics, environmental science, fluid dynamics and agriculture. Yet, to date, except for the tilt stage method, which is extremely limited in range of forces, there is no systematic experimental instrumentation to measure the forces required for drop sliding. We present a new instrument that uses centrifugal forces to slide any drop along a surface. Beyond extending the range of measurable drop-surface interaction, the instrument enables decoupling of some parameters that are bound to be coupled with the simple tilt stage method. Specifically the tilt stage method has two variables varying at the same time: the lateral and normal forces. This violates a fundamental principle of experimental science which leads to obscured understanding of surface characteristics. The CAB avoids this problem. [Preview Abstract] |
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