Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session V33: Block Copolymer Thin Films: Directed Self-AssemblyFocus
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Sponsoring Units: DPOLY Chair: Gila Stein, University of Houston Room: 336 |
Thursday, March 17, 2016 2:30PM - 2:42PM |
V33.00001: Log-rolling block copolymers cylinders So Youn Kim, Ye Chan Kim, Dong Hyup Kim, Na Kyung Kwon, Richard A. Register Shear has been the most effective method to create long range order of micro- or nano- structures in soft materials. When shear is applied, soft particles or polymers tend to align along the shear direction to minimize the viscous dissipation, thus transverse (so-called “log-rolling”) alignment is unfavored. In this study, for the first time we report the transverse alignment of cylinder-forming block copolymers. Poly(styrene-b-methyl methacrylate), PS-PMMA, can form a metastable hemicylinder structure when confined in a thin film, and this hemicylinder structure can align either along the shear direction, or transverse to the shear direction (“log-rolling”), depending on the shearing temperature. This unusual “log-rolling” behavior is explained by the different chain mobility of the two blocks in PS-PMMA; the rigidity of core cylinder is the critical parameter determining the direction of shear alignment. [Preview Abstract] |
Thursday, March 17, 2016 2:42PM - 2:54PM |
V33.00002: Laser Zone Annealing - Accelerated Route to Self-Assembled Nanostructures Pawel Majewski, Kevin Yager, Atikur Rahman, Charles Black We present Laser Zone Annealing -- a novel technique of accelerated self-assembly of block copolymer thin films utilizing laser light. In our approach, the laser beam, focused to a narrow line, is rastered across the polymer film coated on the light-absorbing substrate, inducing rapid and highly localized temperature transients in the film. By coupling our method with soft-shear, we demonstrate monolithic alignment of various cylinder-forming block copolymers over extremely short timescales. We utilize the aligned block copolymer films as templates for inorganic nanomaterials pattering. After delivery of inorganic precursors via aqueous or gaseous route, the polymer matrix is ashed leading to extremely well-ordered arrays of inorganic, metallic or semiconducting nanowires. Subsequently, we demonstrate how more complex nanostructures can be created with LZA including multilayered nanomeshes with symmetries beyond the conventional motifs accessible by native block copolymers. We investigate a perspective use of the inorganic arrays as transparent conductors or chemical sensors and characterize their anisotropic electro-optical properties. [Preview Abstract] |
Thursday, March 17, 2016 2:54PM - 3:06PM |
V33.00003: Block Copolymer Directed Self-Assembly Approaches for Doping Planar and Non-Planar Semiconductors. Bhooshan Popere, Boris Russ, Andrew Heitsch, Peter Trefonas, Rachel Segalman As electronic circuits continue to shrink, reliable nanoscale doping of functional devices presents new challenges. While directed self-assembly (DSA) of block copolymers (BCPs) has enabled excellent pitch control for lithography, controlling the 3D dopant distribution remains a fundamental challenge. To this end, we have developed a BCP self-assembly approach to confine dopants to nanoscopic domains within a semiconductor. This relies on the supramolecular encapsulation of the dopants within the core of the block copolymer (PS-$b$-P4VP) micelles, self-assembly of these micelles on the substrate, followed by rapid thermal diffusion of the dopants into the underlying substrate. We show that the periodic nature of the BCP domains enables precise control over the dosage and spatial position of dopant atoms on the technologically relevant length scales (10-100 nm). Additionally, as the lateral density of 2D circuit elements approaches the Moore's limit, novel 3D architectures have emerged. We have utilized our BCP self-assembly approach towards understanding the self-assembly our micelles directed by such nanoscale non-planar features. We show that the geometric confinement imposed by the hard feature walls directs the assembly of these micelles. [Preview Abstract] |
Thursday, March 17, 2016 3:06PM - 3:42PM |
V33.00004: Directed Nanoscale Assembly of Graphene Based Materials Invited Speaker: Sang Ouk Kim Graphene based materials, including fullerene, carbon nanotubes and graphene, are two-dimensional polymeric materials consisting of sp2 hybrid carbons. Those carbon materials have attracted enormous research attention for their outstanding material properties along with molecular scale dimension. The optimized utilization of those materials in various application fields inevitably requires the subtle controllability of their structures and properties. In this presentation, our research achievements associated to directed nanoscale assembly of B- or N-doped graphene based materials will be introduced. Graphene based materials can be efficiently processed into various three-dimensional structures \textit{via} self-assembly principles. Those carbon assembled structures with extremely large surface and high electro-conductivity are potentially useful for energy and environmental applications. Aqueous dispersion of graphene oxide shows liquid crystalline phase, whose spontaneous molecular ordering is useful for display or fiber spinning. Along with the structure control by directed nanoscale assembly, substitutional doping of graphene based materials with B- or N- can be attained \textit{via} various chemical treatment methods. The resultant chemically modified carbon materials with tunable workfunction, charge carrier density and enhanced surface activity could be employed for various nanomaterials and nanodevices for improved functionalities and performances. [Preview Abstract] |
Thursday, March 17, 2016 3:42PM - 3:54PM |
V33.00005: Direct Immersion Solvent Annealing of Nano-filled Block Copolymer Films Melanie Longanecker, Arvind Modi, Guangcui Yuan, Sushil Satija, Joona Bang, Alamgir Karim The addition of nanoparticles to polymer films is a strategic approach to enhance film properties such as optical, thermal, hardness, conductivity, permeability etc. with inorganic components while maintaining an easily processable polymer matrix. To this end, the ``annealing'' of block copolymers while immersed directly in a chamber of solvent is examined to determine its efficacy in ordering nano-filled block copolymer films. Previously we have shown that it is possible to order neat block copolymer films in a mixture of solvents, and this research follows up that work. Specifically, we observe and utilize the effects of direct immersion solvent annealing (DIA) on lamellar poly(styrene-b-methyl methacrylate) thin films with loadings of gold nanoparticles as high as 25 percent by mass. Neutron reflection confirms that DIA is a viable technique applicable to ordering these highly loaded, nano-filled block copolymer systems. Some notable differences exist with respect to results on conservation of domain spacing that may be beneficial to film barrier properties, accomplished with minimal disruption of order and fast kinetics that is compatible with roll-to-roll techniques. [Preview Abstract] |
Thursday, March 17, 2016 3:54PM - 4:06PM |
V33.00006: Effects of ultra-fast solvent evaporation in solvent vapor annealed cylinder-forming block polymer thin films A. Baruth, G. Nelson, C. Drapes, J. Wong, M. Grant Despite continued advances in directed self-assembly of block polymer thin films \textit{via }solvent vapor annealing, a standardized process remains absent. There remain several complicating factors, notably solvent evaporation rate. Recent theoretical models point to this rate dominating the propagation of a given morphology into the bulk of a thin film following nucleation from the free surface. During this drying process, the film undergoes a competition between thermodynamically driven phase separation and kinetically controlled chain mobility. We, among others, have demonstrated that faster solvent removal can enhance propagation down to the substrate. Perpendicularly aligned cylinders are one illustrative example. To further quantify this effect, and look at ultra-fast time scales, we have constructed a solvent vapor annealing chamber that computer-controls evaporation times down to 15 ms. \textit{In situ} spectral reflectance, with 10 ms temporal resolution, monitors the swelling and evaporation. We will present results on cylinder-forming polystyrene-\textit{block}-polylactide thin films swollen to near disorder with tetrahydrofuran, followed by immediate solvent evaporation. Our data reveals control over evaporation times, ranging from 15 ms to several seconds, and the discovery of various evaporation types, previously undetected, including linear, exponential and combinations. Furthermore, atomic force micrographs correlate surface morphologies (both free and substrate) of the resultant films with each evaporation condition. Funded by Nebraska EPSCoR. [Preview Abstract] |
Thursday, March 17, 2016 4:06PM - 4:18PM |
V33.00007: Fabrication of nanoporous block copolymer films using highly selective solvents and non-solvent extraction Changhuai Ye, Bryan Vogt Nanoporous polymeric films with high porosity are necessary for some applications, such as anti-reflective coating. A simple and relatively environmental benign method is developed to fabricate nanoporous block copolymer thin film with tunable porosity up to 69{\%} based on selective solvent swelling of the majority phase and subsequent rapid extraction with a miscible non-solvent (water). Poly(butylnorbornene)-block-poly(hydroxyhexafluoroisopropyl norbornene) (BuHFA) is used to generate these porous thin films due to its high T$_{\mathrm{g}}$ (\textgreater 300 °C) and the selectivity of primary alcohols towards HFA. The porosity of these nanoporous films is highly dependent on the solvent quality for HFA. The modulus of the as-prepared nanoporous BuHFA thin films with the porosity from 0{\%} to 69{\%} was investigated by surface wrinkling and a scaling law of modulus versus density was obtained. These nanoporous thin films act as anti-reflective coatings and an increase in transmittance from approximately 92{\%} to 99.1{\%} (average for the full range of visible light) was obtained for double-side coated glass slides. This methodology is simple and highly tunable; extension to other block copolymer systems is likely possible if sufficient solubility contrast between segments exists. [Preview Abstract] |
Thursday, March 17, 2016 4:18PM - 4:30PM |
V33.00008: Tracking Solvent Distribution in Block Polymer Thin Films with In Situ Solvent Vapor Annealing during Neutron Scattering Cameron Shelton, Ronald Jones, Joseph Dura, Thomas Epps Solvent vapor annealing (SVA) is a potential route to controlling the self-assembly of block polymer nanostructures in thin film geometries as it harnesses the ability to tune substrate surface, free surface, and polymer-polymer interactions simultaneously. However, the effect of parameters such as solvent preference and solvent partial pressure on nanostructure self-assembly is still poorly understood. Herein, we quantified the degree of preferential segregation of d-benzene into polystyrene domains of cylinder-forming poly(styrene-b-isoprene-b-styrene) as a function of film thickness and solvent partial pressure. Additionally, measurable changes in lateral domain spacing, vertical layer spacing, film thickness, and the number of stacked domains at set partial pressures were used to determine how solvent-polymer interactions affected nanostructure reorganization. These in situ experiments were conducted with a combination of small-angle neutron scattering (SANS) and neutron reflectivity (NR), which allowed us to obtain a 3-D profile of solvent distribution and nanostructure self-assembly. By studying the underlying solvent-polymer interactions, this work provides an improved understanding of the mechanisms responsible for nanostructure reorganization during SVA. [Preview Abstract] |
Thursday, March 17, 2016 4:30PM - 4:42PM |
V33.00009: Continuous and patterned deposition of functional block copolymer thin films using electrospray Kristof Toth, Hanqiong Hu, Myungwoong Kim, Padma Gopalan, Michael Loewenberg, Chinedum Osuji The delivery of sub-micron droplets of dilute polymer solutions to a heated substrate by electrospray deposition (ESD) enables precisely controlled and continuous growth of block copolymer (BCP) thin films. The ESD process overcomes many shortcomings of spin coating deposition, including the batch nature of the process, loss of potentially valuable polymer, limitations of solvent choice, and large time scales of annealing. We report that high substrate temperatures led to vertically oriented cylindrical microdomains of poly(styrene-block-methyl methacrylate) (PS-b-PMMA) at the film surface independent of the solvent composition and deposition rates utilized. Conversely, low substrate temperatures resulted in morphologies that were more sensitive to these parameters, with poorly ordered films of globular structures. We also report on the new possibility for patterned deposition of BCP films by spatially varying the electric field at the substrate using an underlying charged grid. To overcome surface charging, a novel alternating current electrospray process is proposed for deposition on non-conductive surfaces. [Preview Abstract] |
Thursday, March 17, 2016 4:42PM - 4:54PM |
V33.00010: Formation of Lamellar Heterolattices in Block Copolymer Thin Films by Sequential Electrospray Deposition Youngwoo Choo, Hanqiong Hu, Kristof Toth, Chinedum Osuji Electrospray deposition (ESD) of block copolymers (BCPs) on a heated substrate provides precise control over the formation of BCP thin films. This continuous deposition process allows one to fabricate heterogeneously assembled thin films by altering the deposition materials. Here, we demonstrate such the sequential ESD of lamellae-forming poly(styrene-$b$-4-vinylpyridine) BCPs with differing molecular weights and explore the morphology of the composite films. The resulting structure of the heterolattice interface was a strong function of temperature. Sharp interfaces with abrupt changes in the lamellar period (L$_{0})$ were observed at lower deposition temperatures (150 - 170 \textdegree C), while higher temperature (190 \textdegree C) produced a smooth variation in the lamellar period from one molecular weight to the next. Furthermore, the ordering kinetics of a secondary layer which was deposited onto the primary layer could be substantially enhanced depending on the molecular weight of the polymer present in the underlying primary layer. We elucidate these findings in the context of temperature and molecular weight dependent diffusion dynamics of the polymers in the melt which control the inter-mixing of the layers. [Preview Abstract] |
Thursday, March 17, 2016 4:54PM - 5:06PM |
V33.00011: Hierarchical assembled nanostructures of hydrogen-bonded supramolecular block copolymer thin films. Xiaofang Chen, Yongchen Cai Controlling the microdomain orientation and long-range ordering in block copolymer thin films is very important in a number of applications, such as nanotemplate, nanoporous thin film, and data storage media. The hierarchical assemblies of block copolymers PS-$b$-P4VP with dendronized small molecules (DM) hydrogen-bonded onto P4VP blocks were investigated in thin films after solvent vapor annealing. P4VP/DM could form lamellar or hexagonal columnar structure with the periodicity around 8 nm, depending on the stoichiometry of the complex. Hierarchical assemblies of PS-$b$-P4VP(DM)x, including lamellae-within-lamellae, cylinder-within--lamellae, and cylinder-within-cylinder, were simultaneously ordered and oriented in thin films, which have been studied systematically with the help of AFM, TEM and GISAXS technologies. The orientation of supramolecular assembly depends on the P4VP(DM) fraction and can be tailored by varying the DM to P4VP ratio. Structural transitions from cylinders of (P4VP/DM), lamellae, to cylinders of PS could be achieved by simply increasing the ratio of DM to 4VP units in block copolymer systems. [Preview Abstract] |
Thursday, March 17, 2016 5:06PM - 5:18PM |
V33.00012: ABSTRACT WITHDRAWN |
Thursday, March 17, 2016 5:18PM - 5:30PM |
V33.00013: Crystallization induced block copolymer assembly at curved liquid-liquid interface Hao Qi, Tian Zhou, Hao Zhou, Christopher Li In a selected solvent, amphiphilic block copolymers can self-assemble into various micelle structures which find widespread applications in nanomedicine. Herein we report a directed assembly of poly (l-lactide acid)-b-poly (ethylene glycol) (PLLA-b-PEG) at curved oil/water interfaces. Oil droplets were dispersed in water phase upon sonication with amphiphilic PLLA-b-PEG as the surfactant. Subsequent crystallization of PLLA segments resulted in the formation of lamellasomes consisting of crystalline PLLA shell and densely-grafted (approx.1chain/nm2) PEG layer. The structure, morphology, and mechanical properties of these unique polymer ensembles were investigated using transmission electron microscopy and atomic force microscopy. Detailed formation mechanism will be discussed in detail. [Preview Abstract] |
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