Bulletin of the American Physical Society
2007 APS March Meeting
Volume 52, Number 1
Monday–Friday, March 5–9, 2007; Denver, Colorado
Session X17: Structure and Dynamics of Polymer Films |
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Sponsoring Units: DPOLY Chair: Joona Bang, Korea University Room: Colorado Convention Center 102 |
Friday, March 9, 2007 8:00AM - 8:12AM |
X17.00001: In-situ Nanoparticles Direct Self-Assembly of Block Copolymer Thin Films. Ranjan Deshmukh, Gavin Buxton, Nigel Clarke, Russell Composto Nanocomposite films have been prepared by thermally decomposing the organometallic precursor, (1,1,1,5,5,5-hexafluoroacetylacetonato)silver(I), AgHFA, in block copolymer poly(styrene-b-methyl methacryalate), PS-b-PMMA films. The decomposition of AgHFA at 185 \r{ }C results in the in-situ formation of silver nanoparticles (Ag NP) distributed throughout the PS-b-PMMA films. RBS, AFM and TEM were used to study the depth profile of silver, evolution of the surface and internal block copolymer morphology for films containing 0, 2, 3.5 and 5-wt {\%} Ag. The in-situ formed Ag NP segregate to the surface of the PS-b-PMMA films and influence the self-assembly process of the block copolymer and vice versa. The Ag NP selectively partition into the PMMA block of the perpendicular lamellae at the surface forming high-density 1D arrays at the surface. The Ag NP further retard the kinetics of flipping from the perpendicular to parallel lamellae morphology at the surface. As the Ag content is increased from 0 to 5-wt {\%} the perpendicular lamellae morphology is completely pinned (i.e. metastable). We have also used cell dynamic simulation (CDS) method to capture the evolution of block copolymer morphology by varying the substrate-polymer interactions. [Preview Abstract] |
Friday, March 9, 2007 8:12AM - 8:24AM |
X17.00002: Real-Time Guided Wave Depolarized Light Scattering of Block Copolymer Thin Films during in Situ Annealing Jeffrey Wilbur, Nitash Balsara, Zhuangxi Fang, Maurice Newstein, Bruce Garetz The guided wave depolarized light scattering technique for measuring grain structure in block copolymer thin films has been further developed to enable us to measure scattering in films heated above the glass transition temperature. We previously published work in which we used a prism to couple a plane-polarized beam into and out of the transverse magnetic (TM) mode of a glassy polymer film, measured the extent of depolarized scattering into the transverse electric (TE) mode within the film, and correlated the intensity of the TE signal to grain structure. Through the design and incorporation of a grating coupler system in which the polymer film is deposited onto the coupler itself, we have supplanted the prism coupler and removed the requirement that the measured film be glassy, enabling measurements of grain structure during annealing. Coupled with our recently developed theoretical solution for GWDLS, we are able to analyze the grain structure averaged over a 1 cm cross section of a film as it changes in real time. [Preview Abstract] |
Friday, March 9, 2007 8:24AM - 8:36AM |
X17.00003: Structural Characterization of Asymmetric Block Copolymer Thin Films using Resonant Soft X-Ray Scattering J. M. Virgili, J. B. Kortright, N. P. Balsara, R. A. Segalman Resonant soft X-ray scattering (RSOXS) is a powerful tool for structural characterization of block copolymer thin films over very large areas ($\sim $9000 $\mu $m$^{2})$. We study a single layer of cylinders formed from an asymmetric poly(styrene-$b$-isoprene) (PS-PI) block copolymer thin film using X-rays tuned to the carbon $\pi $* resonance. These results are compared to bulk structural data obtained by conventional small angle X-ray scattering (SAXS). We demonstrate that the cylinder-to-cylinder spacing is conserved between the bulk and thin film form. In sphere-forming PS-PI block copolymers, we observe a sphere-to-sphere spacing in thin films that is between the bulk nearest neighbor and bulk lattice spacing. RSOXS' capability in probing complex multi-block copolymers by tuning to different energy edges and also of probing a variety of film thickness effects will also be discussed. [Preview Abstract] |
Friday, March 9, 2007 8:36AM - 8:48AM |
X17.00004: Decay length of phase coherent block copolymer films: neutron reflectivity, analytical theoretical and simulation studies Junhan Cho, Kwanwoo Shin, Kwangsoo Cho, Wonyoung Jung, Sangbo Na Phase coherent thin films of symmetric diblock copolymers are investigated to study relationship between processing condition and thermodynamic responses for the manufacture of nanopatterned copolymer films. Temperature effects on phase coherent profiles and their decay lengths for some styrenic block copolymer films are firstly probed by using neutron reflectivity measurements. Pressure effects on those properties are secondly probed by using a recent field-theoretic simulation method for compressible systems. An analytical Landau theory in connection with a molecular model for perturbed hard chains is then introduced to give a molecular prediction of the reflectivity and simulation results for the copolymers. [Preview Abstract] |
Friday, March 9, 2007 8:48AM - 9:00AM |
X17.00005: Silicon Wire Grid Polarizer for Deep UV Fabricated by Diblock Copolymer Lithography Koji Asakawa, Young-Rae Hong, Vincent Pelletier, Douglas Adamson, Richard Register, Paul Chaikin Thin-shaped polarizers able to continuously polarize deep ultraviolet (UV) light below 300 nm were demonstrated using silicon wire grids with a 16.5 nm half-pitch stripe pattern. Conventional wire grid polarizers are capable of polarizing infrared and even some visible light, but are not for wavelengths below 300 nm due to their large pitch. To realize a deep UV polarizer, both a highly reflective material and an ultra-fine stripe pattern are required. While our group recently demonstrated aluminum wire polarizers [1], silicon shows greater reflectivity in the deep UV than aluminum. Block copolymer lithography was used to fabricate this ultra fine stripe pattern. A thin film of cylinder-forming polystyrene-polyhexylmethacrylate diblock copolymer (PS-PHMA, 21-64 kg/mol) was shear-aligned [2] and used as a mask for reactive-ion etching (RIE) to generate the 16.5 nm half-pitch stripe pattern of silicon nanowires on a transparent substrate. The finished polarizer showed polarization ability starting from the visible region and extending below 300 nm, including good polarization efficiency for 200 nm UV light. 1) Pelletier, et. al. Appl Phys Lett, 88, 211114 (2006), 2) Angelescu et al. Adv. Mater. 17, 1878 (2005) [Preview Abstract] |
Friday, March 9, 2007 9:00AM - 9:12AM |
X17.00006: Why Does the Effect of the Free Surface on the Tg-Confinement Effect Depend So Strongly on Polymer Species? John M. Torkelson, Manish K. Mundra The effect of confinement on the glass transition temperature in thin polymer films has been heavily examined in the case of polystyrene and poly(methyl methacrylate). However, related effects have seen very limited study in other polymer systems. Here we demonstrate that simple adjustments to the polymer repeat unit structure leading to a greater requirement for cooperativity of the segmental mobility associated with Tg result in larger effects of the Tg-confinement effect. This is seen both with regard to the magnitude of the reduction in Tg at a given film thickness and with regard to the film thickness at which reductions in Tg from the bulk value are observed. Sets of data in which an increase in the size of a rigid side group (polystyrene vs. poly(4-methyl styrene) vs. poly(t-butyl styrene)) or an increase in the polymer backbone rigidity (polystyrene vs. polycarbonate vs. polysulfone) lead to an increase in the Tg-confinement effect will be described. [Preview Abstract] |
Friday, March 9, 2007 9:12AM - 9:24AM |
X17.00007: Dynamics of water on self-assembled monolayers J. Matthew D. Lane, Michael Chandross, Mark J. Stevens, Gary S. Grest, Christian D. Lorenz Nanoscale surface interactions of water at polymeric interfaces are important for a number of applications including biophysics, nanofluidics and MEMS devices. Using molecular dynamics simulations we investigate the fundamental properties of water at interfaces for a variety of water models and surfaces. We report results for the contact angle and wetting dynamics of TIP3P and SPC/E water on self-assembled monolayers (SAMs) of alkylsilanes on amorphous silica and alkanethiols on gold with various hydrophilic and hydrophobic head groups. For comparison we also investigate water interactions on bare amorphous silica substrates. Simulations of the dynamics of water confined between two surfaces coated with SAMs will also be presented. [Preview Abstract] |
Friday, March 9, 2007 9:24AM - 9:36AM |
X17.00008: Phase Transitions of Hexadecanethiol Self-Assembled Monolayers on Polycrystalline Silver Studied by NanoDSC Liang Hu, Leslie Allen Hexadecanethiol self-assembled monolayers (SAMs) grown on polycrystalline Ag planar surfaces (2D) and nanoparticles (3D) are studied by measuring heat capacity with NanoDSC. Two different melting transitions with peak temperature TM1=115$^{\circ}$C and TM2=127$^{\circ}$C are observed, which indicates two ordered phases exist. SAMs with TM2 are thermodynamically preferred, and the melting characteristics are comparable to that of Ag-Alkanethiolate layered materials precipitated from solution as reported in the literature. Three different states of the system can be obtained by specific heating and cooling schedule: (1) upon fully annealing, a single phase with TM2 is observed; (2) partially annealing results in the coexistence of both phases; (3) upon rapid quenching from high temperature, a single phase with TM1 can be obtained. [Preview Abstract] |
Friday, March 9, 2007 9:36AM - 9:48AM |
X17.00009: Kinetics of growth and assembly of ordered array of non-coalescing water droplets over evaporating polymer solutions Vivek Sharma, Mohan Srinivasarao Breath figures form over cold solid or liquid substrates on contact with humid air. Typically, the water drops exhibit a range of sizes, self-similar growth marked by coalescence in late stages, and final surface coverage is limited to 0.55. Breath figures formed on evaporating polymer solutions in contact with the blast of humid air, have drops that can grow without coalescence, self-assembling into close packed arrays of nearly monodisperse drops with surface coverage approaching 0.90. In this study, we elucidate the mechanism of drop growth, by considering the growth kinetics of a droplet population under the mass and heat transport of water vapor that are intimately coupled with the corresponding fluxes of the evaporating solvent. We examine the role of solvent and polymer in controlling the kinetics of growth and assembly of droplets, which eventually evaporate away producing a polymer film with ordered array of air bubbles. [Preview Abstract] |
Friday, March 9, 2007 9:48AM - 10:00AM |
X17.00010: Molecular Dynamics in Self-Assembled Monolayers Jason Bochinski, Derrick Stevens, Mary Scott, Laura Guy, Casey deDeugd, Laura Clarke Silane self-assembled monolayers (SAMs) are an important tool for both scientific research and technological applications. Despite their widespread use, few experimental investigations have addressed molecular motion within these films, which offer a unique and useful physical system for fundamental scientific studies, such as observing dipolar and other glass transitions in two-dimensions. In addition, relaxations such as ``rotator'' phases where molecular groups rotate in a plane parallel to the surface have been correlated with film conductivity, adhesive, and wetting properties. We utilize surface-sensitive, dielectric relaxation spectroscopy to probe molecular motion as a function of temperature within silane chemistry-based monolayers formed upon interdigitated electrodes. Our latest results exploring a previously published motion as well as comparisons to linear polymer films will be discussed. [Preview Abstract] |
Friday, March 9, 2007 10:00AM - 10:12AM |
X17.00011: Thickness study of Langmuir-Blodgett Films of Copolymers of Vinylidene Fluoride with Trifluoroethylene using X-ray Reflectivity Jihee Kim, Stephen Ducharme, Shireen Adenwalla Nanometer thickness scale control is one of the advantages of ferroelectric polymer films made by Langmuir-Blodgett (LB) deposition technique, compared to conventional techniques, such as solvent spin coating and casting, but polymers do not always form true monomolecular layer. Therefore, film thickness must be calibrated independently. We report measurements of sample thickness using x-ray reflectivity (XRR), a powerful tool to measure the thickness of ultrathin films, which is also suitable for polymer LB films. The XRR data from LB films of copolymers of vinylidene fluoride with trifluoroethylene deposited on thick silicon wafers exhibit up to six interference oscillations. Fitting by the Kiessig fringe method results thickness measurements averaging 2.8 $\pm $ 0.2 nm, 2.6 $\pm $ 0.2 nm, and 2.3 $\pm $ 0.2 nm per LB transfer, for copolymers consisting of 80{\%}, 70{\%} and 50{\%}, respectively, of vinylidene fluoride, which means that 1 LB transfer consists of approximately 6 molecular layers. The results are consistent with ellipsometric measurements made on similar films [M. Bai \textit{et al.}, \textit{J. Appl. Phys. }\textbf{95}, 3372 (2004)]. [Preview Abstract] |
Friday, March 9, 2007 10:12AM - 10:24AM |
X17.00012: Electro-Optic Polymer Films for Reconfigurable Photomask Applications Adam Fontecchio, Anna Fox Holographically formed polymer dispersed liquid crystal (H-PDLC) films have unique electro-optic properties including the ability to selectively reflect or transmit a particular wavelength as a function of bias applied to the film. The proposed application formed in this medium is a real-time dynamically reconfigurable mask for the UV exposure step in the photolithographic process. Current photolithography technology requires a static mask to prevent UV exposure of selected areas on the patterning surface in order to form structures in photoresist. The exposure process must be repeated several times with different masks to fabricate 3D structures. A real-time reconfigurable mask allows simple generation of 3D structures including peaks, valleys, and grades in the resist substrate. The H-PDLC photomask consists of a film array with independent control over each pixel. Bias is applied across the selected pixels to allow UV exposure in that region. Change in applied bias allows transmission, reflection, and grayscale during a single UV exposure. Proof of concept is shown for a 9-pixel array with passive-matrix style control over each pixel. Samples of cured photoresist in several configurations using the 9-pixel mask are evaluated. [Preview Abstract] |
Friday, March 9, 2007 10:24AM - 10:36AM |
X17.00013: Interfacial Characteristics of a Potentially Anti-befouling Highly Rigid Ionomer Christopher J. Cornelius, Cy H. Fujimoto, Lilin He, Dvora Perahia Ionic polymers with a potential to form a water purification membrane inhibit biofouling activity. The onset of biofouling involves release of polysaccharides by bacteria that adhere to the membrane surface, serve as bedding and nutrients and allow further bacterial growth. This stage is controlled by the interfacial energy and morphology of the membranes. It is often followed by irreversible structural changes, as fouling propagates. The surface energy as a function of time of contact with water of sulfonated substituted \textit{para}phenylenes was studied as a first step in understanding the mechanism of adhesion of bacteria to the membrane. Surface energies increase with increasing exposure times of the membranes with water, indicative of rearrangements in which more sulfonated groups migrate to the surface. Ongoing studies are currently on the way to correlate adhesion of alginate, a model polysaccharide and the interfacial characteristics of the membranes. [Preview Abstract] |
Friday, March 9, 2007 10:36AM - 10:48AM |
X17.00014: Interfacial Effects of Nanometer Fluorinated Segments on Energy Controlled Responsive Polymeric Films Dvora Perahia, Alma Gonzales, Dennis W. Smith Jr. Responsive polymeric thin films with controlled surface energy, dielectric constant and structure are critical for a variety of immerging technologies such as microfluidics, nano-electro-optical devices and nano-biotechnology. Introducing nanometer scale fluorinated segments into polymers offers a means to control surface energies and dielectric constants while enhancing significantly the chemical and thermal stability of materials. Fluorinated and protonated segments are highly incompatible and differ in their interfacial affinities. Introducing nanometer scale fluorinated segments offers a mechanism for the polymer to rearrange and respond to changes in the environment while retaining the integrity of the layers. The interfacial energies couples with structure were studies as a function of temperature for PFCB \textit{(perfluoro cynclobutadiene)} based co-polymers. The structure varies from amorphous to liquid crystalline to crystalline with very small variations in comparison to protonated co-polymers. The polymer-air interface is found to be fluorine rich, however interfacial energy is found to be a complex function of the amount of fluorine and the conformation of the fluorinated segments at the interface. [Preview Abstract] |
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