Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session B35: Directed Self-Assembly of Copolymers in Confined Geometry IIFocus
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Sponsoring Units: DPOLY Chair: Chang Ryu, Rensselaer Polytechnic Institute Room: 507 |
Monday, March 2, 2020 11:15AM - 11:27AM |
B35.00001: In-Situ TEM Visualization of Pressure-Induced Ordering of Nanostructured Block Copolymer Thin Films Rong-Ming Ho, Chen-Jung Hung, Shih-Yi Li, Jheng-Wei Lin, Hsiao-Fang Wang, Aum Sagar, Yi-Chien Lee, An-Chang Shi, Apostolos Avgeropoulos, Fan-Gang Tseng, Fu-Rong Chen Here, we aim to suggest a facile and effective method for controlled orientation of block copolymer (BCP) thin films driven by pressure-induced ordering during thermal annealing. A novel chip with a built-up metal wire-based micro heater was fabricated utilizing microelectromechanical system (MEMS) technique to in-situ investigate the morphological evolution of free-standing polystyrene-block-polydimethylsiloxane (PS-PDMS) star-block copolymer thin films for demonstration of the suggested pressure-induced ordering. Owing to the high vacuum (~10-4 Pa) environment, the low pressure could transfer the extremely selective surface to weakly selective surface for the PDMS and PS, giving the neutral air surface for the formation of span-thru perpendicular cylinders with high-degree lateral ordering, as directly visualized by TEM. We believe that this finding will bring the new opportunities for the designs of polymeric materials in practical applications. |
Monday, March 2, 2020 11:27AM - 11:39AM |
B35.00002: Uncovering Hidden Structure in Polymer Films with Soft X-ray Reflectivity Daniel Sunday, Jacob Thelen, Chun Zhou, R. Joseph Kline, Paul F Nealey Studies on lamellar forming block copolymers (BCPs) organized parallel to a substrate are important for understanding assembly in confined conditions and the impact of surface effects. These have typically been conducted using either hard X-rays or neutron reflectivity where the contrast mechanism makes it difficult to distinguish depth dependent structural variations. Using soft X-rays the optical constants of a material can be controlled by varying the energy near an atomic absorption edge. As you approach the edge, the real and imaginary components can change dramatically as a function of functional group type, concentration and orientation. Additionally, unlike hard X-rays or neutrons, the absorption is no longer negligible and shifting energies can significantly change the depth profile of the electromagnetic field, providing additional control over sensitivity as a function of film depth. This technique is applied to two BCP multilayers with different affinities for a surface. Both systems show variations in interface width as a function of substrate proximity, where a strong surface affinity resulted in an increase in the interface width and a weak affinity resulted in a decrease. This type of surface induced behavior has important implications for BCP lithography. |
Monday, March 2, 2020 11:39AM - 11:51AM |
B35.00003: Mapping Self-Assembled Ternary Polymer Blend Phase Behavior Using Gradient Composition Libraries Gregory Doerk, Kristof Toth, Chinedum Osuji, Kevin Yager Blending block copolymers (BCPs) with homopolymers, other BCPs, or nanomaterials is a simple yet powerful way to tune self-assembled structure. However, mapping the composition-dependent phase behavior of polymer blends experimentally is a slow, laborious process resulting in coarse data sets. In response, we have developed a first-of-its-kind user tool that combines electrospray deposition with programmable motor control and gradient solution pumping to generate three-component compositionally graded thin film libraries on single substrates. We describe the creation of thin film libraries featuring blends of polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) BCPs with PS and PMMA homopolymers, and demonstrate how synchrotron small angle X-ray scattering (SAXS) may be used to rapidly characterize the self-assembled domain morphology, spacing, and grain size as functions of blend composition and film thickness. This pairing introduces a high-throughput platform for autonomous characterization that promises to accelerate the discovery, design, and optimization of functional soft matter blends. |
Monday, March 2, 2020 11:51AM - 12:03PM |
B35.00004: Rapid and Tunable Structuring of Block Copolymer Films using Controlled Solvent Swelling Andrew Selkirk, Anna Trubetskaya, Michael Morris, Parvaneh Mokarian We have studied the effect of the film swelling ratio on the phase separation of polystyrene-b-poly(vinylpyridine) (PS-b-PVP) block copolymer (BCP) nanopatterns by precisely controlling solvent uptake into the film. Using a custom-built annealing chamber with an inbuilt reflectometer, swelling ratios of up to 10x were achieved in a controlled vapor environment using a variety of solvents. The swelling behaviour of two different PVP molecular systems were studied, one of low molecular weight (~35 kg/mol) and another of high molecular weight (~800 kg/mol). Our results suggest that above a maximum swelling threshold, the ordering of BCP nanopatterns becomes extremely sensitive to slight variations in temperature and vapor pressure. By precisely controlling such variations, we successfully synthesized a surprisingly varied range of BCP morphologies from these individual systems, including highly sensitive metastable phases. Additionally, in comparison to conventional solvent vapor annealing methods we found that such highly ordered structures could be achieved in a matter of minutes rather than hours. A diffusion model is proposed to explain the kinetic effect, and the route to a rapid self-assembly process in BCP films. |
Monday, March 2, 2020 12:03PM - 12:15PM |
B35.00005: Rapid Vertical Ordering of Lamellar Block Copolymer Films by Dynamic Thermal Gradient Annealing for Ion Conduction Membranes Maninderjeet Singh, Wenjie Wu, Monali N Basutkar, Joseph Walter Strzalka, Alamgir Karim To achieve the full technological potential of block copolymers (BCPs) for use as electrolytes, filtration membranes, or in nanolithography, rapid ordering of BCPs with vertically oriented nanostructures on unmodified substrates is desirable. In this work, we demonstrate the rapid ordering of lamellar BCPs (< 40 s) by utilizing the effect of thermal gradient based Cold Zone Annealing (CZA) technique. The evaporation fronts during film casting results in poorly ordered yet vertically oriented BCP morphology. We demonstrate that CZA, by driving in-plane defect annihilation in such vertically oriented as cast BCP nanostructures, resulted in perpendicularly oriented and well-ordered morphology on a variety of substrates, at short time scales. The kinetics of lamellar grain size (x) evolution was observed to be much faster in CZA (x ~ t0.26) as compared to oven annealing (x ~ t0.15). Subsequent post-annealing integration of Ionic liquid (IL) as a penetrating additive was shown to selectively swell well-ordered lamellar domain by 100%, having potential use for mechanically robust ion-conducting channels in BCP membranes and electrolytes. Such highly swollen and vertically ordered lamellar nanostructures are not obtained by a priori addition of IL to BCP solutions before film casting. |
Monday, March 2, 2020 12:15PM - 12:27PM |
B35.00006: Directed self-assembly of block copolymer thin film with vertical lamellae by applying filtered plasma and repeated shear stress Jinwoo Oh, Jeong Gon Son Directed self-assembly (DSA) of block copolymer (BCP) is a promising technology for nanolithography for semiconductors and nanodevices. Although defect-free BCP lamellar structure with vertical orientation nanopattern is necessary for the wide range of applications of BCP self-assembly, the formation of defect-free BCP lamellar nanostructures with vertical orientation in a large area is still a difficult challenge. In this study, we proposed a new approach of filtered plasma treatment and repeated shear stress on BCP film for directionally aligned and perpendicularly oriented lamellar BCP nanostructure. Shear induced ordering of BCP nanopatterns has been restricted to BCP with spherical and cylindrical nanopatterns because of the interfacial energy difference at surfaces. We introduced filtered plasma on the surface of the BCP thin film to produce crosslinked layer having neutral surface energy, and elastomer film was placed on the surface and subjected to shear stress to create a vertically oriented lamellae. To improve the quality of the alignment of BCP structures, the shear stress was repeatedly applied and defects of the nanopatterns were greatly reduced. Various types of BCP can be aligned with this strategy, and it suggests the potential for application in nanolithography. |
Monday, March 2, 2020 12:27PM - 12:39PM |
B35.00007: Nanotubes from 6-arm star-shaped (PMMA-b-PS)6 thin films So Yeong Park, Chungryong Choi, Eunseol Kim, JunHo Jang, Yeseong Seo, JinKon Kim Fabrication of nanotube arrays has attracted much attention because of potential applications such as photo catalytics and sensors. Although nanotubes have been formed from core-shell cylindrical morphology in a triblock terpolymer, an appropriate solvent annealing should be done. |
Monday, March 2, 2020 12:39PM - 12:51PM |
B35.00008: Nanostructure sizes and interfacial rougness in blends of linear and cyclic block copolymers Amy D Goodson, Maxwell Rick, Jessie E. Troxler, Hank Ashbaugh, Julie Albert Cyclic block copolymers (BCPs) are predicted to assemble into nanostructured domains up to 40% smaller than their linear analogues while exhibiting superior thin film stability and assembly dynamics, properties that are desirable nanolithography. However, synthesizing large quantities of high purity cyclic BCPs is challenging. Thus, we employ dissipative particle dynamic (DPD) simulation to probe the self-assembly behavior of cyclic/linear BCP blends with the aim of answering two questions: How much impact do linear impurities have on cyclic BCP nanostructure size? Can cyclic BCPs be used as structure-directing agents to shrink the domains of linear BCPs in majority-linear blends? Our simulations indicate that up to 10% linear impurity in a cyclic BCP product has a negligible impact on domain spacing and interfacial width, suggesting that costly post-synthesis purification of cyclic BCPs to remove linear impurities may be unnecessary. In majority-linear BCP blends, we find that domain spacing decreases in direct proportion to the amount of cyclic BCP in the blend. These findings provide guidance to experimentalists wishing to utilize cyclic BCPs in nanolithography applications. |
Monday, March 2, 2020 12:51PM - 1:27PM |
B35.00009: Morphological Evolution of Poly(solketal methacrylate)-block-polystyrene in Thin Films Invited Speaker: Thomas Russell Driving the size scale of block copolymer (BCP) microdomains to the nanoscopic level poses numerous challenges in obtaining thin films with highly oriented, laterally aligned structures of large areas. Here, we used the morphological evolution of the lamellar microdomains in thin films of symmetric poly(solketal methacrylate-b-styrene) (PSM-b-PS) BCPs that are converted into poly(glycerol mono-methacrylate-b-styrene) (PGM-b-PS) BCPs by the use of a photoacid generator dissolved in the thin film. This simple hydrolysis, performed in the solid state, causes a marked increase in the segmental interaction parameter, converting a hydrophobic-hydrophobic BCP into a hydrophobic-hydrophilic BCP, wherein the segmental interaction parameter (χ) increased from 0.035 to 0.438 at 25 °C. To orient the microdomains normal to the film surface a hydroxyl-terminated random copolymer (PSM-r-PS) where the fraction of the mers can be varied to tune the interfacial interactions with the substrate and where the (PSM-r-PS) is simultaneously transformed into PGM-r-PS along with the BCPs. The use of the photoacid generator alleviates the need to use toxic vapors and enables a transformation of the BCP in a gradient manner across the substrate that can be used to promote long-range lateral ordering. As the BCP period decreases, the film thickness also must be decreased. Consequently, the ability to use a fully hydrophobic significantly enhances the ability to prepare uniform thin films over large areas. |
Monday, March 2, 2020 1:27PM - 1:39PM |
B35.00010: Ordering and Defectivity in Sub-10 nm Perpendicular Lamellar Block Copolymer Thin Films Alvin Chandra, Ryuichi Nakatani, Takumi Uchiyama, Yuta Nabae, Teruaki Hayakawa The self-assembled nanostructures of block copolymers (BCP) can be used to meet industrial demand for cost-effective methods for forming sub-10 nm lithographic patterns. By applying perpendicular lamellar BCP structures onto thin films, line and space patterns required for lithography can be obtained. However, there remain challenges that must be resolved prior to high-volume manufacturing; the development of strongly-segregating BCPs capable of forming sub-10 nm features, controlling the microdomain orientation into perpendicular structures, and reducing the nanostructure defectivity. Our lab has developed a strongly-segregating BCP, poly(methacrylyl polyhedral oligomeric silsesquioxane)-block-poly(2,2,2-trifluoroethyl methacrylate) (PMAPOSS-b-PTFEMA), that forms sub-10 nm perpendicular lamellae on thin films with ease. To work towards achieving zero defectivity, we studied the growth of ordered structures in PMAPOSS-b-PTFEMA thin films using combinatorial atomic force microscopy (AFM), grazing-incidence small angle X-ray scattering (GI-SAXS), and cross-sectional scanning electron microscopy (CS-SEM). |
Monday, March 2, 2020 1:39PM - 1:51PM |
B35.00011: Boundary-Directed Epitaxy of Block Copolymers Robert Jacobberger, Vikram Thapar, Guangpeng Wu, Tzu-Hsuan Chang, Vivek Saraswat, Austin J Way, Katherine Jinkins, Zhenqiang Ma, Paul F Nealey, Su-Mi Hur, Shisheng Xiong, Michael Arnold Historically, there have been two strategies—graphoepitaxy and chemoepitaxy—for directing the self-assembly of block copolymers (BCPs) into useful nanoscale patterns. We have recently discovered a third paradigm—termed “boundary-directed epitaxy”—in which templates consisting only of planar, low-resolution features are used to drive the formation of more complex BCP patterns with enhanced feature resolution. The templates are comprised of spatial boundaries separating regions on a surface with different composition, formed at the edges of isolated stripes on a background substrate. Vertical BCP lamellae are pinned by chemical contrast at each stripe/substrate boundary, align parallel to the boundaries, selectively form on the stripes (whereas horizontal lamellae form on the background substrate), and register to wide and incommensurate stripes to multiply the feature density. Isolated BCP line arrays with half-pitch of 6.4 nm are demonstrated on stripes wider than 80 nm. Boundary-directed epitaxy circumvents the need for topographic structures used in graphoepitaxy or ultra-narrow guiding features used in chemoepitaxy to direct assembly of sub-10 nm BCP features, and provides an attractive path towards nanofabrication beyond the resolution of conventional lithography. |
Monday, March 2, 2020 1:51PM - 2:03PM |
B35.00012: Effect of chain architectures on the segregation degree of block copolymers Xianwen Ji, Wei-hua Li The design of polymer architectures provides a possible route for lowering the domain spacing of block copolymers in the application of directed self-assembly (DSA). However, the change of segregation degree is always coupled with that of domain spacing. Therefore, we rescale the segregation degrees of different multiblock copolymers with reference to that of AB diblock using self-consistent field theory (SCFT), including [AB]n linear multiblock, AnBn multi-arm star and Ad,nBd,n dendron-like, such that their density profiles of the lamellar morphology are consistent. Then we compare the lamellar periods of these different copolymers under the condition of equivalent segregation degrees. We find that the star and dendron-like architectures can significantly lower the domain spacing relative to that of AB diblock, especially when the arm number or the generation number is large. Our work presents a simple scheme for quantitatively quantifying the reduction of domain spacing of a specific multiblock architecture relative to that of AB diblock and also provides a useful guide for the application of directed self-assembly. |
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