Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session F16: Polymers and Block Copolymers at Interfaces IFocus Recordings Available
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Sponsoring Units: DPOLY DSOFT Chair: Reza Foudazi, University of Oklahoma Room: McCormick Place W-184A |
Tuesday, March 15, 2022 8:00AM - 8:36AM |
F16.00001: DPOLY Invited Talk
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Tuesday, March 15, 2022 8:36AM - 8:48AM |
F16.00002: Composition effects on the air-polymer surface tension in random block copolymers Yuba R Dahal, Juan De Pablo, Paul Nealey, R Joseph Kline, Debra J Audus For lithographic applications, A-b-(B-r-C) copolymers are a promising route for designing defect-free structures with a specified pitch size since the microphase separation can be decoupled from the air-polymer interface. Here we use Polystyrene (PS) as the A block and modified-PGMA (Poly(Glycidyl methacrylate)) as the B and C blocks. Chemistries of B and C are chosen in such a way that air-polymer surface tension for PS is between that of B and C. For perpendicular lamellae, the surface tension of A should be balanced by the surface tension of B-r-C by varying the relative ratio of B to C. One simplified approach for predicting this ratio is to assume that the surface tension of B-r-C is linear function of composition. Here we probe this assumption using all atom MD simulations. An understanding of how composition affects surface tension allows for informed design and reduction of the synthetic burden of A-b-(B-r-C) copolymers. |
Tuesday, March 15, 2022 8:48AM - 9:00AM |
F16.00003: The Effect of Size Properties and End/Linking Group Chemistry on the Surface Mechanical Properties of Water Spread PS-PEG Micelles on the Water Surface Daniel Fesenmeier, You-Yeon Won The surface-mechanical properties of PS-PEG micelles are influenced by the PEG corona structure. Changes in micelle aggregation number as well as changes in the PEG end group and linking group chemistry of the PS-PEG block copolymer are expected to alter PEG corona characteristics and therefore affect surface mechanical properties of the resulting micelle film formed from spreading micelles at the air-water interface. Different sized micelles comprised of PS-PEG block copolymer chains were formulated by equilibrating micelles in different ratios of acetone/water mixtures and subsequently removing acetone using dialysis. Additionally, micelles of a similar size and PS-PEG molecular weight but slightly different chemistry were formulated. The reduction in micelle aggregation numbers results in the subsequent monolayer having higher compressibility moduli and bending stiffnesses and collapsing at lower surface pressures. Micelle hydrophobicity, which is found to change with size and chemistry, does not correlate well with the ability for the monolayer to achieve high surface pressures, but does affect the isotherm shape and the ability for the micelles to respread after collapse. |
Tuesday, March 15, 2022 9:00AM - 9:12AM |
F16.00004: Interfacial assembly of star block copolymers at the water-oil interface Zhan Chen, Christian Steinmets, Jan-Michael Carrillo, Bryan Coughlin, Wenxu Zhang, Jeremiah A Johnson, Bobby G Sumpter, Thomas P Russell We synthesized a series of star block copolymers (s-BCPs) polystyrene-b-poly(2-vinylpyrindine) (PS-b-P2VP), where the PS blocks form the core and P2VP blocks comprise the corona. These s-BCPs were fully dissolved in toluene and the interfacial behavior of droplets of these s-BCPs solutions against water was investigated by pendant drop tensiometry. The P2VP becomes hydrophilic when it come into contact with the aqueous phase and is protonated. This converts the P2VP block into a strongly hydrophilic block, forcing a configurational change of the s-BCPs at the interface. By varying the pH, the degree of protonation can be changed. The lowest interfacial tension was found near a pH of 3.10, while a spontaneous wrinkling of the interfacial assembly was observed for the pH of 0.65, indicating an oversaturation of the interface with highly protonated s-BCPs. s-BCPs can also be introduced to the interface by dispersing the s-BCPs in the aqueous phase. Behavior like that seen with functionalized nanoparticles was observed. The arm number, molecule weight and volume ratio were varied to investigate the dependence of evolution of the interfacial tension on these parameters and elucidate different kinetic pathways for the assembly. |
Tuesday, March 15, 2022 9:12AM - 9:24AM |
F16.00005: Assembly of Polyelectrolyte Star Block Copolymers at the Oil-Water Interface Jan-Michael Carrillo, Zhan Chen, Benjamin L Doughty, Thomas P Russell, Bobby G Sumpter We present results of coarse-grained molecular dynamics simulations of the assembly of star block copolymers at the oil-water interface. The star block copolymer consist of three arms where each arm is a hydrophilic-hydrophobic block copolymer where the hydrophobic blocks are covalently attached to each other forming the core. The hydrophilic corona are modeled to become protonated when in contact with the aqueous phase, massively increasing the hydrophilicity of this block, changing the nature of the star. This results in a conformational change of the star at the interface, significantly stretching the chains comprising the hydrophilic corona into the aqueous phase, while the hyrdrophobic core remains solubilized in the oil phase. We follow the kinetics of the anchoring and assembly of the star block copolymer at the interface, monitoring their lateral assembly, and the subsequent reconfiguration of the star and the change in the interfacial tension, as the degree of protonation increases. At low fractions of protonation, the arm cannot fully anchor to the aqueous side of the interface and interacts with other arms in the oil phase forming a percolated network near the interface. |
Tuesday, March 15, 2022 9:24AM - 9:36AM |
F16.00006: Rapid assembly in block copolymer thin films by sequential solution and thermal annealing with asymmetric reversible processing Kshitij Sharma, Ali Masud, Aman Agrawal, John F Ankner, Sushil K Satija, Jack F Douglas, Alamgir Karim Processing pathways significantly impact block copolymer (BCP) self-assembly in thin films. These processing methods may include thermal annealing (TA), direct immersion annealing (DIA), solvent vapor annealing (SVA), etc. Tuning the annealing environment by parallel/sequential processing via different techniques may lead to previously unexplored pathways that rapidly achieve equilibrium (Eq.) morphologies and even new microstructures. With this research, we propose a sequential annealing method coupling TA with DIA to process BCP films. We first demonstrate the series process of DIA followed by TA, where short time DIA rapidly produces metastable lamellar domains of size Lo/2 (Lo = Eq. size) that transform into domains of size Lo on successive TA at an accelerated rate (higher than direct TA). We then studied the reverse transition from TA to DIA microstructure, where we observed notable asymmetry in the reversibility kinetics as the DIA treatment caused instability in TA'ed BCP films for molecular weights beyond entanglement, before producing the metastable state. The chain rearrangement mechanisms between the metastable and Eq. BCP morphologies are analyzed in terms of film swelling, chain diffusion, and in-plane vs. out-of-plane interfacial evolution. |
Tuesday, March 15, 2022 9:36AM - 9:48AM |
F16.00007: Polarized Soft X-ray Scattering to Interrogate Molecular Orientation in Block Copolymers Daniel Sunday, Dean M DeLongchamp Block copolymers (BCPs) are attractive materials for nanopatterning applications at length scales between 5-50 nm. Patterning at future lithographic nodes will require BCPs with periodicities below 10 nm length scales, where the properties near the interface become increasingly important. However, direct experimental characterization of properties such as the extent of chain orientation near the interface remains challenging. Polarized soft X-ray scattering (PRSoXS) is one potential route for interrogating these properties. Polarized soft x-rays are sensitive to the molecular orientation of specific chemical bonds, and there has recently been significant progress towards quantitative interpretation of PRSoXS patterns. Measurements have been conducted on a series of BCPs with variations in chemistry and molecular weight and characterized with PRSoXS at both the carbon and oxygen edge. The results of these measurements show polarization induced anisotropy in the scattering pattern, which are indications of molecular orientation in the system. The relationships between the molecular orientation and predictions of BCP interface width will be discussed. |
Tuesday, March 15, 2022 9:48AM - 10:00AM |
F16.00008: Structure of Twin Boundaries in Tubular Block Copolymers Edwin L Thomas, Xueyan Feng, Michael S Dimitriyev The appearance of twin boundary (TB) mirror defects in tubular double gyroid (DG) and double diamond (DD) networks suggests the networks can readily adapt into new low energy structures. In the DG, the networks are trihedral with the smallest loop of 10 nodes; in the DD, the networks are tetrahedral with the smallest loop of 6 nodes. There are no mirror symmetries in DG, while there are many types of mirror planes present in the DD. A twin plane in the DG acts as a topological mirror, causing the right-handed and left-handed DG networks to reverse chirality across the TB. The TB occurs on the (422) plane and intersects and alters the nodes in both DG networks via formation of 3 new types of achiral, mirror-symmetric nodes (2 trihedral and 1 tetrahedral) and the appearance of 2 new classes of achiral loops. In the DD, the 2 networks are identical and achiral, just translationally shifted. One of the networks has its nodes offset from the (222) TB plane while the other has nodes on the mirror. The offset network has precisely the same structure as a (111) twin in carbon diamond. For the 2nd network of the DD, the twin results in formation of 2 new types of mirror symmetric nodes (alternating pentahedral and trihedral nodes) which form planar hexagonal loops. |
Tuesday, March 15, 2022 10:00AM - 10:12AM |
F16.00009: Order-order phase transitions of block copolymers within microspheres Wenpeng Shan, Edwin L Thomas Various geometrical and topological transformational pathways have been proposed for order-order phase transitions (OOTs) between different block copolymer phases (e.g. lamellae ↔ double gyroid ↔ cylinder). Often, OOTs are studied as a function of temperature and/or solvent content using small angle x-ray scattering (SAXS). However, the specifics of the morphological evolution at the interface between the co-existing phases are challenging to determine from reciprocal space data. Tomographic electron microscopy imaging in real space can reveal the evolution of the intermaterial dividing surface (IMDS) shape across the boundary between the phases. However, tomograms from microtomed thin sections suffer from including only a relatively small number of unit cells from each phase as well as distortions arising from the microtome slicing. We employ microspheres of polystyrene-polydimethylsiloxane (PS-PDMS) diblock copolymers made by a membrane emulsion process to initially create a concentric layer lamellar structure. By very slowly infiltrating a preferential solvent into the microparticles, phase transitions are induced from lamellae to catenoid-lamellae to double gyroid. 3D tomograms of the interface between the transforming phases provide detailed information on the variation of the IMDS during the OOT. |
Tuesday, March 15, 2022 10:12AM - 10:24AM |
F16.00010: Template-free alignment of lamellar block copolymers for large area sub-10 nm patterning and hybrid nanowire-nanoparticle structures Maninderjeet Singh, Wenjie Wu, Chenhui Zhu, Joseph W Strzalka, Krzysztof Matyjaszewski, Michael R Bockstaller, Jack F Douglas, Alamgir Karim The template-free alignment of BCPs for sub-10 nm patterning, which is needed for the stand-alone use of BCPs in patterning, has not been achieved to date. In this work, we show the template-free alignment of lamellar BCPs for sub-10 nm patterning and generating hybrid nanostructures over large areas. We use zone annealing-soft shear for the self-assembly and the alignment of the vertically oriented lamellar BCPs confined between neutral layers. Furthermore, we use these aligned BCP templates to generate large area aligned gold nanowires having tunable dimensions. We extend the use of shear alignment of BCPs to atom transfer radical polymerization (ATRP) synthesized polymer grafted nanoparticles (PGNPs) and BCP blends. We demonstrate the use of the aligned PGNP-BCP blends to generate hybrid metallic nanowire-dielectric nanoparticle structure with precise placement, by converting one of the BCP domains to gold nanowires and etching the organic materials. These hybrid nanostructures show distinct plasmonic resonance with a shift of peak intensity of 15 nm as compared to neat gold nanowires. These findings open avenues to design novel nanostructures having applications in nanopatterning, electronics, optical and magnetic materials. |
Tuesday, March 15, 2022 10:24AM - 10:36AM |
F16.00011: Selective Swelling Induced Pore Modification in Thin Films of Block Copolymer Active Water Purification Membranes Khadar B Shaik, Ali Ammar, Kshitij Sharma, Diana Cousins, Maninderjeet Singh, Deepalekshmi Ponnamma, Mohammad K Hassan, Samer Adham, Mariam S Al Ali Al-Maadeed, Anil K Bhowmick, Alamgir Karim The self-assembling characteristics of block copolymers (BCPs) provide a promising pathway in developing ultrafiltration membranes with continuous nanoporous channels. Such uniquely defined morphologies can be further tuned by selectively partitioning an active species into the pore-forming domain of BCP. In this report, we present an asymmetric etch-generated membrane possessing a high density of pores when cast using a poly(styrene)-b-poly(4-vinlypyridine) (PS-b-P4VP) BCP. The porous structure in the ~120 nm thick selective BCP film has been optimized for a less tortuous path by controlling the choice of solvent mixtures and later placed on polyethersulfone support layer. This membrane assembly exhibits water flowrates above 1000 Lm-2h-1bar-1 while maintaining the uniform distribution of nanopores. Furthermore, the pores in the membrane have been altered by adding homopolymer and solvent blends and later using quaternization process. The effect on pore properties with increasing etching time and blend concentrations has been studied using Atomic Force Microscopy which showed an increasing trend from 30-70 nm in pore diameter. These results indicate related enhancement of properties for high-performance membranes. |
Tuesday, March 15, 2022 10:36AM - 10:48AM |
F16.00012: Understanding Compatibilization Mechanisms for Upcycling of Semi-Crystalline Mixed Polymers Using Neutron Scattering Xiaomin Tang, Xiayu Peng, Changwoo Dong, Christopher Bowland, Jong Keum, Tomonori Saito, Jihua Chen, Christopher J Ellison, Chelsea Chen Upcycling of mixed waste plastics is challenging as most of the packaging plastics are immiscible. Compatibilization is one of the most promising strategies to upcycle mixed waste plastics. In this work, poly(ethylene terephthalate) (PET) and low density polyethylene (LDPE) are used as a model polymer blend. Two compatibilizers are compared, a PET-PE multiblock copolymer (MBCP) and a PE-PET-PE triblock copolymer (TBCP). A previous study has demonstrated MBCP’s superior efficacy at strengthening the interface over TBCP[1]. To elucidate the compatibilization mechanism of MBCP, small angle neutron scattering (SANS) is used to probe the interfacial structure of compatibilized and uncompatibilized PET/LDPE blends by selectively deuterating the matrix PET and LDPE. The main finding of the work is that MBCP forms a large structure at the interface while TBCB does not. These findings on the interface structure of the compatibilizers in the blends provide insights on the design of effective and customized compatibilizers for diverse plastic mixtures. |
Tuesday, March 15, 2022 10:48AM - 11:00AM |
F16.00013: Mechanical detection of liquid evaporation in thin polymer films using a quartz crystal microbalance Ana Zaalishvili, Yannic Gagnon, Connie B Roth, Justin C Burton The physics of thin, deposited polymer films are more complex than their bulk or macroscopic counterparts. Often these films are deposited by spin-coating from solutions, where the solvent evaporates and leaves behind the polymer. However, evaporation can be inhibited by the solvent mobility within the drying film, and solvent molecules can be trapped indefinitely. The presence of these residual solvent molecules can affect material properties. We used a quartz crystal microbalance (QCM) to explore the timescales and mass loss during evaporation in thin polystyrene films deposited by spin-coating from toluene solutions. Monitoring the mechanical resonance frequency of the QCM reveals sub-monolayer changes in mass. We spin-coated polystyrene films of thickness < 1 micron on the QCMs and found that 10-25% of the residual toluene solvent remained in the film. Part of the solvent left the samples through evaporation, and the rest through heating the sample above the glass transition temperature and annealing in vacuum. The change in mass vs. time can be fit well with two exponential timescales. For a 1 micron thick film, these timescales are 0.7 hours and 4.8 hours. If we interpret the data with a 1D diffusion model with a homogenous diffusion coefficient, we estimate that D ~ 10-16 - 10-17 m2/s |
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