Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session A04: Polymers and Block Copolymers at Interfaces IFocus
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Sponsoring Units: DPOLY DSOFT Chair: Reza Foudazi, University of Oklahoma Room: Room 127 |
Monday, March 6, 2023 8:00AM - 8:36AM |
A04.00001: Periodic and Aperiodic Sphere Packings: A Window into Scale-Invariant Self-Assembly of Amphiphilic Materials Invited Speaker: Mahesh Mahanthappa A zoo of low symmetry, tetrahedrally close-packed Frank-Kasper (FK) phases that mimic the structures of metals and their alloys have recently been discovered in amphiphilic materials, such as small-molecule thermotropic and lyotropic liquid crystals (LCs), and high molecular weight block copolymers and giant shape amphiphiles. While the specific chemical interactions directing these assemblies substantially differ, we describe a common framework for understanding the emergence of periodic FK A15 and σ phases and related dodecagonal quasicrystals. This talk will then describe how our discovery that simple additives in lyotropic LCs expands the range of accessible phases translates into blends of particle-forming diblock copolymers with various core-segregating homopolymer additives. These findings furnish enticing opportunities to identify length scale-invariant molecular design principles across amphiphile that classes that could possibly translate to their interfacial activities and applications. |
Monday, March 6, 2023 8:36AM - 8:48AM |
A04.00002: Thermoresponsive ultrafiltration membrane from polymerization of lyotropic liquid crystals Younes Saadat, Kyungtae Kim, Reza Foudazi In this work, we present the fabrication of a two-step thermoresponsive ultrafiltration (UF) membrane through polymerization of a lyotropic liquid crystal (LLC). A lamellar LLC is produced from a mixture of poly[(ethylene oxide)100-block-(propylene oxide)65-block-(ethylene oxide)100], water (containing ammonium persulfate as the initiator), and polymerizable oil (n-butyl acrylate/ethylene glycol dimethacrylate). Differential scanning calorimetry is employed to evaluate the thermoresponsive behavior of the polymerized LLC (polyLLC). Two-step thermoresponsiveness (~35 °C and ~50 °C) of the polyLLC is observed due to the lower critical solution temperature (LCST) of block copolymer and melting of the crystalline structure of the polyethylene oxide (PEO) block. The obtained mesophase is then cast on a nonwoven polyester support sheet followed by thermal polymerization to form a supported UF membrane. The hydration capacity, water flux, water flux recovery after fouling, and molecular weight cut-off (MWCO) of the obtained membrane are evaluated at different temperatures to examine its thermoresponsiveness. The experimental results reveal that the UF membrane has a reversible thermoresponsive behavior at the LCST and PEO melting of polyLLC. Additionally, the MWCO of the membrane can be altered with temperature due to the pore size change with temperature stimulus. |
Monday, March 6, 2023 8:48AM - 9:00AM |
A04.00003: Contrast-variation resonant soft X-ray scattering for multicomponent soft matter thin films Dean M DeLongchamp, Kristof Toth, Eliot H Gann, Daniel Sunday Multicomponent thin films of soft materials can present complex and unique morphologies not present in the bulk owning to the interplay of enthalpic interactions and entropic factors at the film interfaces. Surface level microscopy and other conventional characterization techniques lack the high spatial resolution and chemical sensitivity to ascertain individual component contributions. Although small angle neutron scattering (SANS) can achieve contrast variation through synthetic deuteration in monotonic radiolabeled series, the technique is limited to bulk samples (>1 mm) because of low neutron flux, thus being inaccessible for the thin film regions of interest. Our approach to solving this issue is using contrast-variation resonant soft X-ray scattering (CV-RSoXS), which is a powerful synchrotron-based characterization tool that can produce SANS-like patterns in short (10 s) exposures of ≈100 nm thin films at 90° incidence, with high contrast due to intrinsic element and bond sensitivities. |
Monday, March 6, 2023 9:00AM - 9:12AM |
A04.00004: Probing Chain Orientations in Block Copolymer Thin Films with Polarized Soft X-ray Scattering Daniel Sunday, Eliot H Gann, Dean M DeLongchamp Block copolymers (BCPs) self-assemble into periodic morphologies with length scales between 5-100 nm, with the presence of the interface between components implying a degree of preferential orientation of the polymer chains. Characterizing the chain orientation will provide important insights into the self-assembly of BCPs, particularly as higher χ systems begin to play an important role in applications such as directed self-assembly. However, experimental characterization of molecular orientation distributions in amorphous soft matter remains a significant challenge. Polarized soft X-ray scattering (P-RSoXS) utilizes the interactions of soft X-rays with molecular dipoles to provide a probe of molecular orientation in organic materials. P-RSoXS measurements were conducted on a series of thin films of lamellar polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA), and evidence for molecular orientation in those films was observed in the scattering patterns near the absorption peaks for both the aromatic rings in PS and the carbonyl bond in PMMA. These scattering patterns are fit with a data fusion approach that combines real space information about the composition distributions with a series of candidate orientation functions in order to extract quantitative orientation distributions. |
Monday, March 6, 2023 9:12AM - 9:24AM Author not Attending |
A04.00005: Defect Patterning for the Directed Self-Assembly of Block Copolymers using Polymer Pen Nanolithography Jacob LaNasa, Kyungtae Kim Block copolymers (BCPs) with two or more immiscible and covalently linked blocks will have the propensity to phase separate at the nanoscale. Given sufficient processing, these phase-separated domains conform to periodic structures that have been useful in lithography, optics, and membrane design. Typically, resulting structures are limited in long range order due to uncontrolled nucleation kinetics. A strategy for placing defects on a substrate can assist in the assembly of ordered structures by pre-determining nucleation sites and regulating grain growth. Improved long-range order strengthens photonic response in BCPs and is a key factor in successfully incorporating them into visible-light integrated circuits as waveguides. Here, a substrate is pre-patterned with a poly(dimethylsiloxane) (PDMS) photoresist using polymer-pen nanolithography (PPL). The PPL technique is a novel approach to precise and high throughput application of soft material features onto a surface. The PDMS resist is photopolymerized to yield a chemically selective defect architecture intended to influence the self-assembly of a PDMS-b-poly(ethylene-alt-propylene) BCP previously found to assemble into periodic structures. The structural characteristics of the patten-assisted assembly is analyzed using microscopy and X-ray scattering techniques. |
Monday, March 6, 2023 9:24AM - 9:36AM |
A04.00006: Vacuum-driven orientation of nanostructured diblock copolymer thin films for nanopatterning. Aum Sagar Panda, Yi-Chien Lee, Chen-Jung Hung, Kang-Ping Liu, Cheng-Yen Chang, Gkreti-Maria Manesi, Apostolos Avgeropoulos, Fan-Gang Tseng, Fu-Rong Chen, Rong-Ming Ho Block copolymer (BCP) self-assembly has gained greater attention due to its ability to form well-ordered nanostructures that can be utilized as a bottom-up approach for next-generation lithographic applications, flash memory devices, magnetic storage, templated synthesis, nanofiltration, and so forth. For nanopatterning applications, one of the notorious problems is the high surface tension discrepancy between the constituents of BCP that results in the formation of a wetting layer on the air surface obstructing the perpendicular orientation. Herein, we demonstrate a facile method for controlled orientation of nanostructured BCP thin films. A simple diblock copolymer system, polystyrene-block-polydimethylsiloxane (PS-b-PDMS), is chosen to demonstrate vacuum-driven orientation for solving the notorious surface tension discrepancy problem between the constituents of PS-b-PDMS for nanopatterning. Owing to the pressure dependence of the surface tension of polymeric materials, a neutral air surface for the PS-b-PDMS thin film can be formed under high vacuum degree (~10-4 Pa), allowing the formation of perpendicular cylinders and lamellae at the air surface upon thermal annealing. Accordingly, this approach is also implemented on the polystyrene-block-poly(L-lactide) (PS-b-PLLA) diblock copolymer system. The experimental results are in line with the PS-b-PDMS system indicating generalization of this approach. |
Monday, March 6, 2023 9:36AM - 9:48AM |
A04.00007: Self-Healing Directed Self-Assembly of Block Copolymers for Lithographic Applications Whitney Loo, Hongbo Feng, Ricardo Ruiz, Paul F Nealey The directed self-assembly (DSA) of block copolymers (BCPs) is a lithographic process with significant promise for patterning sub-10nm features and for the use of pattern rectification in EUV lithography. Patterning at these small length scales will require both the design of new polymers that follow specific materials design requirements and tailored approaches to DSA. Here we utilize BCPs with A-b-(B-r-C) copolymer architecture which decouple thermodynamic and surface energy properties to allow for DSA via thermal annealing with low defectivity. Through the use of a high throughput, post synthetic modification, we are able to synthesize a library of A-b-(B-r-C) copolymers based on polystyrene-block-poly(glycidal methracylate) copolymers with copolymer periodicities, L0, between 16-19 nm. While a full set of polymer mat and brushes for conventional DSA is not readily accessible to this new family of A-b-(B-r-C) polymers, we have developed a new, self-brushing chemoepitaxial DSA workflow. The B-r-C random block contains chemical functionality that allows for self-brushing to Si substrates. Through sequential rounds of DSA, the B-r-C domain of the copolymer grafts to the substrate and registers the B-r-C copolymer domain to the pre-pattern with incremental improvement at each DSA cycle, which results in “self-healing” of the DSA defects and a large increase in the DSA processing window. We hope this work will uncover a new understanding between copolymer molecular properties and characteristics of the final pattern such as line edge and line width roughness. |
Monday, March 6, 2023 9:48AM - 10:00AM |
A04.00008: Dynamic Interfacial Fluctuations and Phase Separation Mechanisms Captured in situ with Environmentally Controlled Atomic Force Microscopy Julia Murphy, Jonathan Raybin, Moshe Dolejsi, Genevieve Ansay, Steven J Sibener Block copolymers are of broad interest to both fundamental science and technology applications, providing a platform to study phase separation and self-assembly phenomena or for applications in nanolithography and templating. Here, I present the use of environmentally controlled and high-speed atomic force microscopy (AFM) to study the dynamics of poly(styrene-block-methyl methacrylate) (PS-b-PMMA) thin films in situ above the glass transition temperatures (Tg). Imaging under these experimentally challenging thermal annealing conditions enables in situ observation and measurement of the domain dynamics and self-assembly, including interfacial fluctuations, pattern roughness, and two-dimensional phase separation mechanisms. Topographic confinement in nanoscale lithographic channels induces ordering in the PS-b-PMMA nanopattern. By disabling the slow-scan axis, we achieve an effective imaging time resolution to 50 ms per scan, allowing in situ observation of the dynamic interfacial fluctuations and pattern roughness when imaging at temperatures above Tg. Additionally, we utilize environmentally controlled AFM to track the mesoscale structural evolution of incommensurate PS-b-PMMA thin films without topographic confinement, imaging as the film undergoes thermal annealing to analyze the growth of terraces and holes in situ. From ensemble growth statistics acquired from time series AFM images, we see homogeneous nucleation and growth consistent with classical nucleation theory. Scaling behavior in the coarsening period differs from predictions, but this discrepancy is resolved through image analysis, revealing that Ostwald ripening and coalescence contribute to coarsening simultaneously and we estimate the relative contributions of each mechanism. These experiments together demonstrate the utility of high-speed AFM for capturing polymer dynamics across length and time scales. |
Monday, March 6, 2023 10:00AM - 10:12AM |
A04.00009: Seeing the order-order phase transition between double diamond and double gyroid structures in block copolymers Edwin L Thomas, Wenpeng Shan The order-order phase transition between double diamond (DD) and double gyroid (DG) phases occurs in a variety of soft matter systems including water-surfactant liquid crystal phases and in block copolymers. Various geometrical and topological transformational pathways have been proposed based on limited microscopy and scattering data, but the specific structural features of the morphological evolution at the interface between the co-existing phases have been very challenging to elucidate. Here we employ slice and view scanning electron microscopy on polystyrene-polydimethylsiloxane diblock copolymers to examine the phase transition zone between the DD and DG structures. 3D tomograms of the transformation zone show how the mesoatoms and loops of each network are cooperatively modified over a narrow (less than one unit cell wide) zone that shows a facile, low energy transformation pathway between the tubular network phases. We discuss the malleability of the tubular network mesoatoms and the maintenance of key symmetries between the two cubic phases, i.e. the 4sub1/4sub3 screw axes in the DG shift and align with the 2sub1 screw axes in DD, while certain two fold rotational axes remain unchanged across the phase boundary. |
Monday, March 6, 2023 10:12AM - 10:24AM |
A04.00010: Co-existing Nanostructures of Lamellae and Cylinders by A1BA2C Tetrablock Terpolymer Hyeongkeon Yoon, Qingshu Dong, Weihua Li Nanopatterns with multiple shapes, such as lines and dots, in a single substrate are needed for the next-generation nanolithography. Here, we observed, via small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM), co-existing morphologies of lamellae and cylinders by careful control of volume fraction of each block in polystyrene-b-polyisoprene-b-polystyrene-b-poly(2-vinylpyridine) tetrablock terpolymer (S1IS2V). The PI cylinders are located inside PS lamellae, but close to the interface of PS/P2VP lamellae. The experimentally observed morphology is in good agreement with the predicted phase by self-consistent filed theory (SCFT). Finally, we obtained vertically oriented co-existing nanostructures on a substrate by using solvent vapor annealing (SVA) and confirmed the orientation of co-existing nanopattern by grazing-incidence small angle X-ray scattering (GI-SAXS) and atomic force microscopy (AFM). |
Monday, March 6, 2023 10:24AM - 10:36AM |
A04.00011: Competition between tubular network morphologies in diblock copolymer/homopolymer blends Vivek Subramanian, Benjamin Greenvall, Karen I Winey, Bryan Coughlin, Gregory M Grason, Edwin L Thomas Binary blends (BBs) of diblock copolymer (BCP)/homopolymer (HP) have been shown to be a more accessible way of attaining complex morphologies like Double Gyroid (Ia3d), Double Diamond (Pn3m), and Double Primitive (Im3m) over a wider compositional window. However, these phase assignments have involved either Transmission Electron Microscopy (TEM) projections (real space) that are hard to distinguish, or small angle x-ray scattering (SAXS) (reciprocal space) which are also equivocal. BBs of poly(styrene)-b-poly(isoprene) and (polystyrene)-b-poly(butadiene) (PS-b-PX) (X = PI/PB) with the respective low Tg PI or PB homopolymers (HP) were solution cast and annealed (125 C, 1 week). The HP component can occupy either the minority (channels) or majority (matrix) domains and act as wet or dry brush additives depending on the HP chain length relative to the respective block length. Real space Slice and View Scanning Electron Microscopy (SVSEM) tomography, reciprocal space 3D Fast Fourier Transform (FFT) and microfocus synchrotron SAXS are employed to unambiguously determine the tubular network structures. Experimental analysis is compared to newly computed SCFT calculations of BBs which aim to correlate thermodynamic shifts in network stability to sub-domain geometric features, including molecular packing of the BCP “host” morphology and spatial localization of the HP “guest” within it. |
Monday, March 6, 2023 10:36AM - 10:48AM |
A04.00012: Bio-inspired amphiphilic heteropolymer dynamics at interfaces Shayna Hilburg, Tianyi Jin, Alfredo Alexander-Katz Amphiphilic synthetic random heteropolymers can provide a bio-inspired means for augmenting and even mimicking bio-macromolecular function. The statistical distribution of chains makes analysis of particular molecules and motifs challenging experimentally. Through molecular dynamics simulations, we can provide nanoscale analysis of individual sequences to provide insight into how these synthetic polymers respond to their environments. Having previously shown multiple dynamic modes and heterogeneous surfaces for the chains in aqueous solution, we now characterize their statistically derived properties in more complex environments. We demonstrate that mixing solvents and small molecules alter not only the driving forces to assembly, but also introduce high energy interfaces that can stimulate changes in polymer conformation. These changes are shown to be highly dependent upon the physicochemical properties of both the polymer and the interface. Our characterization, leveraging analysis techniques from both polymer physics and protein sciences, illuminates avenues for modifying and processing synthetic polymer assemblies in solution. |
Monday, March 6, 2023 10:48AM - 11:00AM |
A04.00013: End-on Chain Orientation of Poly(3-hexylthiophene)-Containing Rod-Rod Diblock Copolymer via Controlled Regioregularity-Induced Microphase Separation Philgon Kim We synthesized amphiphilic poly(3-hexylthiophene)-block-poly(3-(2-methoxyethoxy)methylthiophene) copolymer (P3HT-b-P3MEGT) with a regioregularity (RR) of P3HT block having 82 %. At this RR value, the crystallinity of the P3HT was reduced and the microphase separation prevails over the crystallization effect. The synthesized P3HT-b-P3MEGT showed well-ordered lamellar nanostructures after thermal annealing above the melting point of P3HT block. P3HT-b-P3MEGT thin films showed parallel oriented lamellar nanostructures to the substrate because of a large difference of surface tension between hydrophobic P3HT and hydrophilic P3MEGT. Parallel oriented lamellar nanostructure induced end-on orientation of P3HT and P3MEGT chains, which enhances significantly the vertical hole mobility more than 30 times compared to P3HT continuous thin films with edge-on orientation. |
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