Bulletin of the American Physical Society
APS March Meeting 2010
Volume 55, Number 2
Monday–Friday, March 15–19, 2010; Portland, Oregon
Session B19: Focus Session: Thin Films Copolymers I |
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Sponsoring Units: DPOLY Chair: Paul Nealy, University of Wisconsin Room: B118-B119 |
Monday, March 15, 2010 11:15AM - 11:51AM |
B19.00001: Multifunctional Block Polymer Thin Films for Templating and Separations Invited Speaker: Self-assembled block polymer thin films are useful for applications that rely on coatings or freestanding structures that are compositionally heterogeneous on a nanometer length scale. For example, AB diblock copolymers such as poly(styrene)-poly(methyl methacrylate) have been broadly utilized as thin film templates for various nanopattern transfer processes that are attractive for microelectronics applications. In addition, self-assembled block polymer films have garnered interest in the area of gas and liquid separations based their inherent ability to simultaneously incorporate both selective domains and mechanically robust domains needed for practical membrane applications. Motivated by the tremendous technological potential of block polymer thin films, we have explored the incorporation of multiple functional blocks into these hybrid macromolecules that (i) expand the range of accessible nanostructures and (ii) contain the chemical functionality essential for a particular targeted application. These efforts often require the controlled synthesis of multiblock polymers from monomers with chemical features that are well suited to the ultimate intended use. For example, we have incorporated selectively crosslinkable, hydrolytically degradable, proton conducting, and/or reactive ion etch resistant materials into a variety of di-, tri- and multiblock structures using combinations of controlled polymerization techniques. We have used thin films of these block polymers for the preparation of nanostructured magnetic materials in addition to ultrafiltration, gas separation, and fuel cell membranes. In this presentation I will discuss our recent efforts in the synthesis, self-assembly, and implementation of multifunctional block polymer thin films for applications in templating and separations. [Preview Abstract] |
Monday, March 15, 2010 11:51AM - 12:03PM |
B19.00002: Discrete Nanopatterns from Block Copolymer Self-Assembly Ho-Cheol Kim, Sang-Min Park, Charles Rettner, Jed Pitera Self-assembled block copolymers in thin films have been studied extensively due to their potential applications to surface patterning alternative to conventional photolithography. In fact, the length scales of microdomains of block copolymers, which range typically 10 nm to 50 nm are very attractive for future technology generations of semiconductor devices. Tremendous progress has been made for controlling the orientation and the lateral placement of microdomains of block copolymers on surfaces as a result of numerous research groups' effort. While continuous periodic patterns with small number density of defects are desirable for most applications, discrete patterns with controlled lateral placement are necessary for fabricating devices as well. In this paper, we report a simple and effective method to create discrete surface patterns from lamellar microdomains of block copolymers. We used topographic surface patterns to control the orientation of lamellar microdomains. This approach provides line/space patterns with desirable length at precisely controlled positions on substrates. Detailed control parameters for this approach will be discussed based on the surface energy of substrates and the confinement of block copolymers. [Preview Abstract] |
Monday, March 15, 2010 12:03PM - 12:15PM |
B19.00003: Simulation of Line Edge Roughness in Weakly Segregated and Strongly Segregated Diblock Copolymer Resists August Bosse We discuss phase-field simulations of $A$--$B$ interfacial roughness (\textit{i.e.}, ``line edge roughness'') in weakly segregated and strongly segregated $AB$ diblock copolymer resists. Line edge roughness---in particular, long-wavelength line edge roughness---can be especially troublesome for resist scientists because of its ability to disrupt final device function. We examine the relative magnitude \textit{and} spectral character of long-wavelength line edge roughness in weakly segregated and strongly segregated $AB$ diblock copolymer resists using a stochastic version of the Leibler-Ohta-Kawasaki phase-field theory of block copolymer ordering [T. Ohta and K. Kawasaki, \textit{Macromolecules} \textbf{19}, 2621 (1986)]. [Preview Abstract] |
Monday, March 15, 2010 12:15PM - 12:27PM |
B19.00004: Enhanced Alignment of Block Copolymer Domains by Controlled Film Thickness and Interfacial Interactions on Chemically Patterned Surfaces Hyo Seon Suh, Kookheon Char In this presentation, we focus on the self-aligning behavior of symmetric diblock copolymers on flat but chemically heterogeneous substrates defined by conventional photolithography. Laterally heterogeneous substrates with relatively large feature size ($>$ 5$L_{0})$ were prepared by the first neutralization of organosilicate (OS) substrates followed by the selective oxidation of the OS substrate using O$_{2}$ RIE on a PR pattern placed on the energetically neutral OS substrate. The thermal annealing of block copolymer (BCP) films placed on these substrates resulted in featureless BCP films on the oxidized regions as well as well-defined line patterns aligned perpendicularly to the boundary lines between the two energetically different regions on the OS substrate. We found that these BCP nanostructures were influenced by BCP film thickness as well as the surface energy of the neutral OS region. By varying a set of these parameters, we could successfully obtain energetically favorable and self-aligned BCP films. In addition, we will discuss a strategy for improving the alignment of BCP microdomains while maintaining such parameter sets. Our approach taken here could give an insight on the process windows for the enhanced alignment of microdomains in the directed assembly of BCP thin films. [Preview Abstract] |
Monday, March 15, 2010 12:27PM - 12:39PM |
B19.00005: Phase behaviour of ABC Triblock Copolymer Thin Film Confined Between Brush-coated Substrates Rong Wang, Gi Xue In this work, we investigate the phase behavior of ABC triblock copolymer thin film confined between brush-coated substrates by using the self-consistent field theory in three dimensions. The coated polymers identical with the end block A and the middle block B of the ABC triblock copolymer are considered. The phase diagrams are constructed by continuously changing the compositions of the block copolymer. At the three corners of the phase diagram, the disordered phase or the core-shell hexagonal phase is easily form. When the three components are comparable, the lamellar phase occurs. When the ABC block copolymer confined between the end block copolymer coated substrates, the parallel lamellae is easy to form. But for the middle block B coated substrate, the direction of the lamellae can be tailored by the interaction parameters and the composition of the block copolymer. Even the direction of the cylinder phase can be tuned. Our results show that the surface properties of the substrates are very important to control the phase behaviour and are helpful for designing the functional nanopattern of the ABC block copolymer thin film. [Preview Abstract] |
Monday, March 15, 2010 12:39PM - 12:51PM |
B19.00006: Transformation of the Boundary Conditions for Density Multiplication by Directed Assembly of Block Copolymer-Homopolymer Blends and Molecular Transfer Printing Guoliang Liu, Shengxiang Ji, Paul Nealey Previously we determined the phase behavior of lamellae-forming poly(styrene-\textit{block}-methyl methacrylate) (PS-$b$-PMMA) on interpolated chemical patterns in thin films. The stripe density of the chemical pattern was half of the block copolymer domain density. We observed morphologies such as parallel lamellae, vertical lamellae, mixed lamellae, PS-dots, and PMMA-dots depending on the boundary conditions: the pattern stripe width and the interfacial energies between the blocks and the pattern stripes. Here we found that the block copolymer domain width of vertical lamellae exhibited a bimodal behavior. By directed assembly of block copolymer-homopolymer ternary blends and subsequent molecular transfer printing, the boundary conditions of the chemical patterns were transformed. The printed chemical patterns had a stripe density and a stripe width matching with block copolymer domains. The interfacial energies of the stripes were favorable to the block copolymer domains. Directed assembly of block copolymer on this new chemical pattern removed the domain bimodal behavior and improved the three dimensional block copolymer domain profiles. [Preview Abstract] |
Monday, March 15, 2010 12:51PM - 1:03PM |
B19.00007: Preparation of Surface Patterned Silica from Poly(dimethylsiloxane)-Containing Block Copolymer Thin Films Maurice Wadley, Kevin Cavicchi The self-assembly of block copolymers into ordered nanostructures such as spheres, cylinders, and lamellae in the range of 10-100 nm makes them interesting materials for patterning surfaces. Thin films of poly(dimethylsiloxane) (PDMS)-containing block copolymers are attractive for patterning due to their conversion to silica under ultraviolet/ozone treatment which offers a functional, topographically patterned inorganic substrate. In this work a series of AB block copolymers with PDMS and either a poly(ethyl acrylate) or poly(styrene) block have been prepared via RAFT polymerization. Thin films of these polymers were treated with ultraviolet/ozone to produce periodic, nanoscale silica features. The effect of the mobility of the non-PDMS block on the solvent and thermal annealing of thin films of cylindrical and spherical morphologies will be discussed. [Preview Abstract] |
Monday, March 15, 2010 1:03PM - 1:15PM |
B19.00008: Fabrication of Complex Three-Dimensional Nanostructures from Self-Assembling Block Copolymer Materials on Patterned Surfaces: A computational Study Xianggui Ye, Brian J. Edwards, Bamin Khomami Chemically patterned substrates can direct the assembly of adsorbed layers or thin films of block copolymers. Here, we consider the self-assembly of a lamella-forming diblock copolymer on periodically stripe-patterned substrates. The morphology of the block copolymer follows the pattern at the substrate; however, with an increasing degree of mismatch between the width of the stripe-pattern and the periodic spacing of bulk block copolymer, novel morphologies have been found. Therefore, it is possible to adjust the morphologies in thin bock copolymer films by adjusting the mismatch between the width of the stripe-pattern and the periodic spacing of the bulk block copolymer. These results demonstrate a promising strategy for fabrication of complex interfacial nanostructures from chemically patterned templates. [Preview Abstract] |
Monday, March 15, 2010 1:15PM - 1:27PM |
B19.00009: Buckling of block copolymer lamellae in supercritical carbon dioxide Hideaki Yokoyama, Masateru Ito, Yasuhiro Sakai, Kozo Ito, Kenji Sugiyama Supercritical carbon dioxide (scCO$_2$) swells many kinds of polymers. In particular polymers containing fluorine are highly swollen. Therefore, block copolymers having fluorinated blocks are expected to be swollen selectively in scCO$_2$ due to the higher affinity of scCO$_2$ toward the fluorinated blocks. We studied the phase behavior of fluorinated block copolymers swollen in scCO$_2$ and found multiple order-to-order transitions as a function of pressure. In addition, the swollen structures could be frozen by reducing temperature and subsequently carbon dioxide was removed without disturbing the swollen morphologies. As a result, the volume occupied with carbon dioxide was converted to empty space, and hence a variety of nanoporous structures were successfully formed. In particular we found that swollen lamellae in scCO$_2$ becomes undulated lamellae with a large wavelength, which is similar to ''egg cartoon'' often observed in unbinding membranes of surfactants. [Preview Abstract] |
Monday, March 15, 2010 1:27PM - 1:39PM |
B19.00010: Nanostructured Polymer Membranes for Selective Alcohol Transport Ashish Jha, Liang Chen, Nitash Balsara We have examined the possibility of using A-B block copolymers for selective separation of alcohols from aqueous mixtures. The A block is not soluble in the liquids of interest and serves as the structural block while B serves as the transporting block. The size and geometry of the transporting channels have been controlled by varying the molecular weight and composition of the copolymer. Experimental results that reveal the interplay between membrane transport and underlying membrane morphology will be presented. [Preview Abstract] |
Monday, March 15, 2010 1:39PM - 1:51PM |
B19.00011: Nanoporous membrane based on block copolymer thin film for protein drug delivery Seung Yun Yang, Jeong-A Yang, Eung-Sam Kim, Gumhye Jeon, Eun Ju Oh, Kwan Yong Choi, Sei Kwang Hahn, Jin Kon Kim We studied long term and controlled release of protein drugs by using nanoporous membranes with various pore sizes. Nanoporous membrane consists of the separation layer prepared by polystyrene-block-poly(methylmethacrylate) copolymer thin film and conventional microfiltration membrane as a support. We demonstrate a long-term constant in vitro release of bovine serum albumin (BSA)and human growth hormone ) (hGH) without their denaturation up to 2 months. A nearly constant serum concentration of hGH was maintained up to 3 weeks in SD rats. The long-term constant delivery based on this membrane for protein drugs within the therapeutic range can be highly appreciated for the patients with hormone- deficiency. [Preview Abstract] |
Monday, March 15, 2010 1:51PM - 2:03PM |
B19.00012: An in-situ study of structure evolution in block copolymer thin films of PS-PEO during solvent vapor annealing Parvaneh Mokarian-Tabari, Timothy W. Collins, Michael A. Morris Thin films of block copolymers are promising candidates for producing nano scale structures in the electronic industry such as sub-30 nm templates for nanolithography [1]. To be able to produce structures with desired morphologies and minimum defects, it is important to have a deep understanding of the ordering mechanism. We have carried out a systematic study on spin cast films made of poly(styrene-b-ethylene oxide) block copolymers during solvent and thermal annealing. The swelling behavior of the films were studied by using an environmental cell to control the vapor pressure of the gas and equipped with small angle light scattering apparatus. Our results show that the swelling starts within seconds of exposure to toluene vapor and the domains form within minutes. Cyclic transition between perpendicular and horizontal arrays is observed. [1] Ruiz R, Kang H M, Detcheverry F A, Dobisz E, Kercher D S, Albrecht T R, de Pablo J J and Nealey P F, 2008, \textbf{321, }936 [Preview Abstract] |
Monday, March 15, 2010 2:03PM - 2:15PM |
B19.00013: Structure of Epitaxially Assembled Block Copolymer Domains Gila Stein, J. Alexander Liddle, Andrew Aquila, Eric Gullikson Epitaxial self-assembly of block copolymers is promising for integrated circuit patterning, but it is unclear how the shape of the block copolymer domains is deformed by the epitaxy process, or if the intrinsic roughness of the block copolymer interface is too large to be suitable for manufacturing. We use soft x-ray diffraction to characterize the size, shape, and interface structure of poly(styrene-\emph{b}-methyl methacrylate) (PS-PMMA) block copolymer domains assembled on an epitaxial template. The shapes of the PS and PMMA phases are deformed when the equilibrium domain sizes are incommensurate with the line widths of the underlying template, and mismatch as small as $(7\pm3)$\% produces a PS sidewall angle of $(1.6\pm 0.2)^{\circ}$. The average width of the copolymer interface is ($4.9\pm0.1$) nm. Comparison with mean-field theoretic predictions for the structure of block copolymer interfaces suggests a low-frequency variance in the copolymer interface position of 1.2 nm$^2$, or a low-frequency line-edge roughness of approximately $3\sigma=3$ nm. The low-frequency roughness is attributed to thermal fluctuations, and the magnitude is well-described by a simple capillary wave model for polymer interfaces. [Preview Abstract] |
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