Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session C6: Thin Films - Nanocomposites and Block CopolymersFocus
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Sponsoring Units: DPOLY Chair: Muzhou Wang, Northwestern University Room: 265 |
Monday, March 13, 2017 2:30PM - 2:42PM |
C6.00001: Effect of Graft Polymer Architecture on the Grafted Layer Structure in Polymer Functionalized Nanoparticles. Kevin Modica, Tyler Martin, Arthi Jayaraman Tailoring the physical and chemical features of the graft polymer chains in polymer functionalized nanoparticles allows one to tune the grafted layer structure and control the assembly/dispersion of the nanoparticles. While past theoretical and experimental studies have established the underlying polymer physics in polymer functionalized nanoparticles containing linear homopolymer grafts, much less is known about how non-linear polymer architecture impacts the grafted layer structure. Recent advances in synthesis of polymers with complex new architectures has inspired us to look into the effect of graft polymer architecture on the grafted layer and inter-particle interactions. In this talk, we present our recent theory and simulation studies on comb polymer grafted nanoparticles (CPGPs). We use Langevin dynamics to investigate the effect of particle curvature, backbone grafting density, and sidechain length and spacing within comb graft polymers on the grafted layer of a single CPGP in an implicit solvent. We also use PRISM theory to calculate the effective inter-particle interactions in explicit solvent and linear homopolymer matrix as a function of the comb graft polymer design. [Preview Abstract] |
Monday, March 13, 2017 2:42PM - 2:54PM |
C6.00002: Molecular Dynamics Simulations to Determine the Effects of Copolymer Architecture and Nanofiller Adsorption Strength on Viscoelastic Properties of Polymer Nanocomposites~ Alex Trazkovich, Lisa M. Hall We simulate a simple nanocomposite consisting of a single spherical nanoparticle surrounded by coarse-grained polymer chains. The polymers are composed of two different monomer types, which have different interaction strengths with the nanoparticle.~~ We examine the effect of copolymer sequence and monomer-nanoparticle interaction strength on structure (using the monomer-nanoparticle radial distribution function) and chain relaxation times (using the polymer end-to-end vector autocorrelation function). We also examine relaxations times as a function of distance from the nanoparticle surface in order to understand the effect of copolymer sequence on the range and magnitude of the interphase of slowed dynamics surrounding the nanoparticle. Finally, we use the stress autocorrelation function to calculate the dynamic storage and loss modulus, which we also measured as a function of copolymer sequence, monomer-nanoparticle interaction strength, and distance from the nanoparticle surface. Our work is motivated by tire tread compounds, which are composed primarily of styrene-butadiene rubber copolymer (with potentially controllable block structure) and reinforced with carbon black and/or silica nanoparticles. Our focus on local properties near the nanoparticle surface is expected to reveal trends that are applicable to the bulk properties of these systems. [Preview Abstract] |
Monday, March 13, 2017 2:54PM - 3:06PM |
C6.00003: Position and orientation of gold nanorods in vertical cylinder diblock copolymer films Boris Rasin, Ben Lindsay, Xingchen Ye, Jeffrey Meth, Christopher Murray, Robert Riggleman, Russell Composto The location and orientation of gold nanorods (AuNRs) in diblock copolymer films with a vertical cylinder morphology was studied. Poly(styrene-b-2-vinylpyridine) (PS-b-P2VP) films containing AuNRs grafted with P2VP were prepared and solvent annealed. The solvent annealed films had a microdomain structure of vertical P2VP cylinders in a PS matrix. Nanocomposites (NCs) were prepared with 70 nm x 12 nm and 101 nm x 16 nm AuNRs. For NCs prepared with the shorter and thinner AuNRs, NRs near the surface were found to mainly align parallel to the surface. The AuNRs either bridged two neighboring P2VP cylinders or collocated on top of one P2VP cylinder. For NCs prepared with the longer and thicker AuNRs, the NRs mainly bridged adjacent P2VP cylinders. For greater insight into the system SCFT simulations were used to compare the free energy differences between vertically aligned, bridging and isolated NR positions. In agreement with experiments, simulations demonstrate that the lowest free energy corresponds to NRs that span two cylinders. These simulations also show the expected behavior of the P2VP domains beneath the NR and provide guidance for selecting NR dimensions that would result in vertical orientation. [Preview Abstract] |
Monday, March 13, 2017 3:06PM - 3:42PM |
C6.00004: Self-Assembled Nanorods and Nanoplates in Polymer Nanocomposite Films Invited Speaker: Russell Composto Polymer nanocomposite (PNC) films combine the processibility of polymers with the functional properties, such as electrical conductivity, toughness and transparency, imparted by the type and dispersion nanoparticle. In this work we investigate the assembly of polymer grafted gold nanorods (NRs) in homopolymer and block copolymer films. By tuning brush and matrix molecular weight, the dispersion and alignment (side by side versus end-to-end) of NRs is tailored to control the optical properties, such as a blue or red shift in the surface plasmon resonance (SPR). Simulations to predict thermodynamic conditions for dispersion/aggregation are presented. Moreover, mixed brushes and bimodal brush lengths grafted to NRs are shown to improve dispersion and self consistent field calculations provide insight into the thermodynamic driving force for this behavior. The dispersion of upconverting nanoplates in homopolymer films is also presented. Using cylindrical block copolymer films, NRs locate at the surface and span neighboring vertical domains. Simulations provide a thermodynamic explanation for the preferential location of NRs as a function of length. Finally, a short discussion of nanoparticle dynamics in crowded and confined systems concludes this presentation. [Preview Abstract] |
Monday, March 13, 2017 3:42PM - 3:54PM |
C6.00005: Self-assembly of Polymer-Grafted Magnetic Nanoparticles in Solutions and at Interfaces Siqi Liu, Tsengming Chou, Pinar Akcora We will present the effect of increasing dipolar interactions on the morphology diagram of polystyrene-grafted iron oxide nanoparticles. Uniformity in grafting (attaching chains symmetrically on spherical particles) has important consequences on the aggregation state of large nanoparticles in solution. We will discuss the stability of polymer-grafted magnetic nanoparticles in solution prepared by grafting-to and -from methods, and compare the aggregation states (i.e. lattice framework, well-dispersed) of particles in solvent-cast films. Our results suggest that polymer-grafted particles prepared by grafting-to method aggregate and form a lattice framework. Non-aggregated and stable colloidal solutions are observed with the particles prepared by grafting-from method, which is attributed to the non-uniform distribution of tethered chains on particle surfaces. Moreover, the organization of grafted particles at liquid-air interfaces, and their spatial arrangement and packing with the application of oscillating magnetic fields will be discussed. [Preview Abstract] |
Monday, March 13, 2017 3:54PM - 4:06PM |
C6.00006: Block copolymer patterning by localized magnetic field screening. Manesh Gopinadhan, Youngwoo Choo, Lalit Mahajan, Dennis Ndaya, Rajeswari Kasi, Chinedum Osuji We demonstrate the use of low intensity magnetic fields (sub 1 tesla) to control the orientation of block copolymer microdomains with high fidelity on short timescales. Despite the significant potential, to date, magnetic field control on BCPs was limited to the application of large magnetic fields (\textgreater 3T) generated by either super conducting or complex resistive magnets. Here we explore a facile approach wherein strong BCP alignment by simple rare earth permanent magnets is facilitated by co-assembling small quantities of nematic liquid crystals with side chain liquid crystalline block copolymers (LC BCPs). The resulting textured morphologies display orientational order parameters close to unity. The low field response is principally due to a significant reduction in viscosity and the concomitant enhancement of alignment kinetics and increase in the average BCP grain size due the presence of nematogens. Further, low field application results in localized field curvature and modulation of field intensity in the vicinity of periodic arrangements of cobalt magnetic nanostructures enabling localized variation of block copolymer orientation. This development opens up new avenues of highly localized spatial control of BCPs using low cost permanent magnets and nanoparticle assemblies. [Preview Abstract] |
Monday, March 13, 2017 4:06PM - 4:18PM |
C6.00007: Using Block Co-Polymers to Create a Metal Oxide Hard Mask for Etching Silicon and Silicon Dioxide Omar Cervantes, Luis Castro, Noel Arellano Moore's Law has been achievable using lithography techniques for decades. However, lithography techniques are getting more expensive and difficult due to the wavelength of light and the limitations of optical systems currently used to pattern transistors. Our proposal involves using block-copolymers (BCP) to create the patterns necessary to achieve a line width which defines the critical dimension of a transistor. BCP have been shown to create patterns with line widths around 10 to 14 nanometers. Our specific internship goal was to develop an etch-resistant metal oxide mask defined by a lamellae BCP pattern. We began the process by creating fingerprint BCP patterns using spin casting techniques on surface of a silicon or silicon dioxide wafer. Then, we removed one of the polymers after they have self-assembled using an oxygen plasma etch. After, the empty space was filled with a metal oxide using an atomic layer deposition (ALD) tool. Next, we removed the top layer of metal oxide to reveal the remaining polymer block. Finally, we remove the remaining polymer block leaving behind the metal oxide mask. This allowed us to selectively etch into the silicon or silicon dioxide. This technique can achieve spacing smaller than being used today. [Preview Abstract] |
Monday, March 13, 2017 4:18PM - 4:30PM |
C6.00008: Preparation of PVMS-b-PMMA block copolymer with potential for oil-water separation Baraka Lwoya, Md Uddin, Sourav Chatterjee, Julie Albert We report herein the synthesis of poly(vinylmethylsiloxane-\textit{block}-methyl methacrylate) (PVMS-$b$-PMMA) by a combination of anionic synthesis of PVMS, ATRP of PMMA, and then co-joining the end-group functionalized blocks with a click reaction. In using this combination of methods, we were able to effectively control both molecular weight and polydispersity in polymers that were otherwise challenging to synthesize by sequential block addition.~Following thin film nanostructure alignment by either thermal or solvent annealing, exposure to UV light cross-links the siloxane copolymer block, which imparts mechanical integrity, and degrades the sacrificial PMMA block in a single step to produce a nanoporous film. The hydrophobicity and nano-porosity of these films are desirable characteristics for their application as membranes for oil/water separation. [Preview Abstract] |
Monday, March 13, 2017 4:30PM - 4:42PM |
C6.00009: Neutron Reflectometry and Small Angle Neutron Scattering of ABC Miktoarm Terpolymer Thin-Films Matthias M. L. Arras, Weiyu Wang, Jyoti P. Mahalik, Kunlun Hong, Bobby G. Sumpter, Gregory S. Smith, Sergey Chernyy, Hyeyoung Kim, Thomas P. Russell Due to the constraint of the junction point in miktoarm terpolymers, where three chains meet, ABC miktoarm terpolymers are promising to obtain nanostructured, long-range ordered materials. We present details of the thin-film structure of ABC miktoarm terpolymers in the poly(styrene), poly(isoprene), poly(2-vinylpyridine) (PS-PI-P2VP) system, investigated by neutron reflectometry and small angle neutron scattering. To this end, we synthesized partially deuterated versions of the PS-PI-P2VP and investigated annealed samples, spin-coated to various thicknesses of the bulk repeat period. Furthermore, we investigated the structural change upon selective blending with homopolymers or fullerenes. We find that thin-film constraints on the morphology can vanish after only twice the repetition period. In addition, it is indicated that nanoparticles improve the ordering in these systems, however, this seems to be not necessarily true for homopolymer blending. [Preview Abstract] |
Monday, March 13, 2017 4:42PM - 4:54PM |
C6.00010: Non-native block copolymer nano-structures Kevin Yager, Pawel Majewski, Atikur Rahman, Aaron Stein, Greg Doerk, Gwen Wright, Charles Black We present emerging strategies for constructing three-dimensional nanostructures whose shapes and symmetries go beyond those of the bulk equilibrium block copolymer phase diagram. Photo-thermal methods can be used to control block copolymer ordering; ordered layers can be stacked to yield new lattice symmetries. This multi-layered ordering strategy can also be performed in a responsive mode, where each self-assembled layer templates the ones that follow. Finally, we describe how blending allows the self-assembling film morphology itself to be responsive to underlying guide patterns. Taken together, these new motifs represent a toolbox for constructing 3D nanostructures with symmetries and complexity far beyond the conventional self-assembled morphologies. [Preview Abstract] |
Monday, March 13, 2017 4:54PM - 5:06PM |
C6.00011: Order enhancement in shear-aligned block copolymer thin films with solvent vapor annealing Ye Chan Kim, So Youn Kim Despite a great ability to create various nanoscale structures of block copolymers (BCPs) through microphase separation, defects formed during the ordering process often obstruct a successful lithographic application of BCPs. Reducing a defect density along with low line edge roughness is required for many device applications. Chemical guiding patterns has been considered; however, it is difficult to impart long range orders. Here, we introduce a defect melting showing that significant amount of defects of BCPs in thin film can be reduced with proper solvent annealing. Cylinder forming polystyrene-b-poly(2-vinylpyridine) is firstly shear-aligned and then exposed to the various solvents. Grazing incidence small-angle X-ray scattering (GISAXS) and SEM image analysis were used to conduct quantitative analysis of solvent vapor annealing for reducing defect density. GISAXS data clearly shows the appearance of high order peak and the peak sharpening with solvent vapor annealing, implying increased grain size. We also show that solvent selectivity for blocks is important for order enhancements. [Preview Abstract] |
Monday, March 13, 2017 5:06PM - 5:18PM |
C6.00012: Enhanced Self-Assembly Kinetics in Symmetric Ternary Block Copolymer Blends. Gregory Doerk, Pawel Majewski, Aaron Stein, Kevin Yager, Charles Black In this talk, we discuss recent work investigating the kinetics of topological ordering in thin films of symmetric, lamellae-forming polystyrene-b-poly(methyl methacrylate) (PS-PMMA) blended with equal parts of much smaller molecular weight PS and PMMA homopolymers. When using thermal annealing to promote order, 50{\%} (w/w) homopolymer blends exhibit a dramatic increase in the power law exponent for pattern coarsening when compared to neat PS-PMMA, resulting in long-range order for short annealing times. The blends are also compatible with solvent vapor annealing in tetrahydrofuran vapor. This enables self-assembly in 50{\%} (w/w) homopolymer blend films comprising PS-PMMA with molecular weight \textgreater 500 kg/mol where orientational correlation lengths exceed 10 times those of the neat PS-PMMA under the same conditions. [Preview Abstract] |
Monday, March 13, 2017 5:18PM - 5:30PM |
C6.00013: Beneath the Surface: Understanding Patterns of Intra-Domain Orientational Order Ishan Prasad, Youngmi Seo, Lisa Hall, Gregory Grason Block copolymers (BCP) self assemble into a rich spectrum of ordered phases due to asymmetry in copolymer architecture. Despite extensive study of spatially-ordered composition patterns of BCP, knowledge of orientational order of chain segments that underlie these spatial patterns is evidently missing. We show using self consistent field (SCF) theory and coarse-grained molecular dynamics (MD) simulations that, even without explicit orientational interactions between segments, BCP exhibit generic patterns of intra-domain segment orientation, which vary both within a given morphology and from morphology to morphology. We find that segment alignment is usually both normal and parallel to the interface within different local regions of a BCP sub-domain. We describe principles that control relative strength and directionality of alignment in different morphologies and report a surprising yet generic emergence of biaxial segment order in morphologies with anisotropic curved interfaces, such as cylinders and gyroid phases. Finally, we focus our study on cholesteric textures that pervade mesochiral BCP morphologies, specifically alternating double gyroid (aDG) and helical cylinder (H*) phases, and analyze patterns of twisted (nematic and polar) segment order within these domains. [Preview Abstract] |
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