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 W05: Hybrid and Multicomponent Polymer Materials Containing Nanoparticles IFocus
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Sponsoring Units: DPOLY Chair: Robert Hickey, The Pennsylvania State University; Russell Composto, University of Pennsylvania Room: Room 128 |
Thursday, March 9, 2023 3:00PM - 3:12PM |
W05.00001: Role of blend asymmetries on the thermodynamics of highly confined polymer nanocomposites Anastasia Neuman, Trevor Devine, Daeyeon Lee, Robert A Riggleman Infiltration of polymer blends into the interstices of dense nanoparticle (NP) packings leads to the formation of highly loaded nanocomposites with unique mechanical and transport properties. Polymers in such nanocomposites are subjected to extreme physical confinement which alters the thermodynamics of the blend, increasing miscibility over their bulk counterparts. Additionally, these polymers are exposed to a very large nanoparticle surface area, increasing the impact of polymer-NP interactions on equilibrium behavior, particularly when one polymer in the blend has a stronger affinity for the NP surfaces. Here we present a computational study using field theoretic simulations to investigate the impact of polymer-nanoparticle interactions on the phase separation dynamics and equilibrium structure of polymer blend nanocomposites. We find that asymmetric polymer-NP interactions increase the window of miscibility of polymer blends, working in tandem with physical confinement to further increase the critical point. In the limit of very strong surface interactions, we observe a transition to pore-scale phase separation with one polymer phase wetting the nanoparticle surfaces. In addition, we introduce asymmetry in chain length and stiffness to explore diverse composite structures with potential for experimental development. |
Thursday, March 9, 2023 3:12PM - 3:24PM Author not Attending |
W05.00002: Applying macromolecular crowding models to simulations of cellulose nanocrystals assembly Jiaxin Hou, William Sampson, Ahu G Dumanli Self-assembly is a common phenomenon used by nature to organize matter to create multifunctional structures from molecular to macroscale. Cellulose nanocrystals (CNCs), are charged anisotropic particles that can spontaneously assemble into left-handed chiral nematic structures. Generally, the assembly of colloidal particles is a function of concentration, aspect ratio (AR), and polydispersity. While it is relatively easy to understand the main drivers of self-assembly through modeling these parameters, the left-handed chirality and the origin of twisting the CNC-based self-assembled systems are still debatable. To address this, we applied the crowding factor (CF), a parameter defined by the combination of AR and concentration, to facilitate the chiral twist in CNCs’ self-assembly using a molecular dynamic coarse-grained method with Gay-Berne potential. |
Thursday, March 9, 2023 3:24PM - 3:36PM |
W05.00003: Hybrid Thermoplastic Elastomers using Bottlebrush Block Copolymer Grafted Nanoparticles Jensen Sevening Thermoplastic Elastomers (TPEs) are physically crosslinked polymer networks with extensive applications due to their unique mechanical properties and ease of processing. Current TPEs are limited by a narrow modulus range and low melting points, restricting the working range of processed parts. A potential method for overcoming such shortcomings is the use of bottlebrush polymers in which the polymer backbone is densely grafted with polymer chains, resulting in entanglement-free systems which aid in lowering the modulus of the material. An additional tuning parameter to increase elastomer functionality is to add inorganic nanoparticles, providing increased thermal stability and toughness, and from a structural standpoint, acting as “permanent” junction sites of the network. Here, the self-assembled structure and mechanical properties of a series of bottlebrush poly(dimethyl siloxane)-poly(styrene) (PDMS-PS) diblock copolymer grafted silica nanoparticles with varying polymer molecular weights and block volume fractions were investigated using a combination of X-ray scattering, transmission electron microscopy, and mechanical testing. It is found that the PDMS forms the soft deformable matrix while the microphase separated PS domains create network junctions. The synthesized bottlebrush block copolymer grafted nanoparticles demonstrate potential advantages over current thermoplastic elastomers by showing tunable mechanical and physical properties. |
Thursday, March 9, 2023 3:36PM - 3:48PM |
W05.00004: Formation of nanoparticle-block copolymer hybrids in competitive solvents Jaroslaw Paturej, Labeesh Kumar, Andriy Horechyy, Bhanu Nandan, Jaroslaw S Klos, Jens-Uwe Sommer, Andreas Fery We investigate the encapsulation of polymer-tethered nanoparticles (NP) inside block copolymer (BCP) micelles, which turns to the mutual stabilization of BCP micelles and NPs by each other. It has been demonstrated, for the first time, that in the presence of co-solvent, which is selective for the core-forming block, the encapsulation of polymer-tethered NPs into the core of pre-formed BCP micelles is feasible. We find that in a certain range of cosolvent volume fraction, NP/BCP hybrid micelles comprising a single NP in micelle core are obtained. Significantly, in the presence of cosolvent the NP-loaded hybrid micelles remain intact, whereas the NP-free (empty) micelles undergo further transformations. In particular, our extensive molecular dynamics simualtions recognize mechanisms for the formation of NP/BCP hybrids, which include a one-by-one adsorption of individual BCP chains onto NP surface, fusion of NP with the pre-formed BCP micelles, or a combination of both mechanisms. The observations from numerical modelling are additionally supported by the results obtained from our experiments. The present work provide new opportunities for the fabrication of BCP-based hybrid nanomaterials having potential applications in drug delivery, diagnostics, catalysis, for energy harvesting materials, optical devices, etc. |
Thursday, March 9, 2023 3:48PM - 4:00PM |
W05.00005: Structure and Rheological Properties of Polymer Nanocomposites with Bimodal Nanoparticle Sizes Seong Min Jo, So Youn Kim Polymer nanocomposites (PNCs) have been used in many polymer-based applications based on their ability to improve the physical properties of clean polymers. To control the physical properties of PNC, many PNC studies have first changed the size of monodispersed nanofillers; however, polydispersed PNC systems have not been much discussed despite the frequent use of polydispersed nanofillers in the practical PNC application. |
Thursday, March 9, 2023 4:00PM - 4:12PM |
W05.00006: Hyperuniform Structure in Polymer-Grafted Nanoparticle Assemblies Daniel Long, Michael Ouweleen, Andrew Drake, Kyoungweon Park, Anesia Auguste, Andrew Gillman, Lawrence Drummy The study of relationships between order and disorder in materials across length scales has been an active topic of research in materials science and finds roots in many natural structures. In addition to ordered structures, exotic disordered states such as those exhibited in hyperuniform materials are also of recent interest. Hyperuniformity in two phase materials is defined by the presence of local disorder, in this respect similar to amorphous materials, but also with highly suppressed long range density fluctuations, similar to crystals. In the field of nanocomposite materials, the particle packing is an important parameter that can be altered to improve or control material properties. With their negligible density fluctuations at long length scales, hyperuniform packing structures exhibit efficient control of electromagnetic and/or mechanical waves. Here we demonstrate the fabrication of hyperuniform polymer grafted nanoparticle thin films using additive polymer processing techniques and characterize their resulting mechanical properties. The degree of hyperuniformity is then correlated to the mechanical properties of the composite determined by Brillouin light scattering and crazing experiments on lattice supports. At fixed polymer molecular weight we find that a bimodal distribution of gold nanoparticle diameters could be used to influence the strength of hyperuniformity. The concepts applied here are expected to influence the design of future component-level materials and structures. |
Thursday, March 9, 2023 4:12PM - 4:48PM |
W05.00007: Self-Assembly of Conjugated Block-Copolymers and Nanoparticles Invited Speaker: Park So-Jung The ability to control the molecular packing and nanoscale morphology of conjugated polymers is important for many of their applications. Here, we present the fabrication of well-ordered nanowire arrays of conjugated polymers and nanoparticles based on the binary self-assembly of a conjugated block-copolymer, poly(3-hexylthiophene)-block-poly(ethylene glycol) (P3HT-b-PEG) and nanoparticles at the air-liquid interface. The presentation will discuss how the binary self-assembly differs from that of prototypical coil-coil type block copolymers and present how we utilize the polymer films for the fabrication of responsive thin film interference colors. |
Thursday, March 9, 2023 4:48PM - 5:00PM |
W05.00008: Elucidation of chain dispersity effect on structure and mechanical properties of brush particle solids Michael R Bockstaller, Ayesha Abdullah, Yuqi Zhao, Jaejun Lee, Zongyu Wang, Krzystof Matyjaszewski, Kevin Ferguson, Levent Burak Kara, Eric Harper, Lawrence Drummy The modification of nanoparticles with polymer chains has emerged as a versatile platform to enable particle building blocks that can be assembled into functional materials with controlled microstructure and enhanced physical properties, such as modulus, toughness, dielectric strength or thermal conductivity. Often, a combination of high inorganic loading and modulus is desired. This contribution will present brush chain dispersity as a ‘design parameter’ that enables the concurrent enhancement of Young’s modulus and fracture toughness, while also facilitating increased inorganic loadings. Brush particle model systems with continuous variation of the chain dispersity were synthesized using modified atom transfer radical polymerization and films were characterized using a combination of indentation, dynamic mechanical analysis as well as small angle scattering, electron imaging and tomography. Structure factor and image analysis in bulk and thin films reveal that microstructure order remains unaffected even in the limit of high dispersity (D ~ 2). The fracture toughness of brush particle solids is found to strongly increase with chain dispersity. This is interpreted to be a consequence of entanglement formation between high molecular chains in disperse brush systems. Analysis of the craze density in brush materials is used to establish a quantitative link between dispersity and entanglement formation. |
Thursday, March 9, 2023 5:00PM - 5:12PM |
W05.00009: Jammed Nanoparticle Structures in Polymer Nanocomposite Films Exhibit Improved Nanomechanical Properties Russell J Composto, Shawn M Maguire, Robert W Carpick, John B McClimon For poly(methyl methacrylate) grafted silica nanoparticles (PMMA-NP) and poly(styrene-ran-acrylonitrile) (SAN) films, unique polymer nanocomposite (PNC) morphologies are generated by controlling the interplay between surface enrichment, phase separation, and wetting. PMMA-NP:SAN films undergo distinct stages of phase evolution, resulting in homogenously dispersed systems, enriched PMMA-NP layers at the PNC interfaces, or three-dimensional bicontinuous structures. Using a combination of atomic force microscopy (AFM), AFM nanoindentation, contact angle goniometry, and optical microscopy, these self-regulated structures exhibit increased elastic modulus, hardness, and thermal stability compared to their analogous PMMA/SAN blends. These studies demonstrate the ability to reliably control surface-enriched and phase-separated nanocomposite microstructures to create coatings with attractive properties such as wettability, toughness, and wear resistance. In addition, these morphologies lend themselves to broader applications, including: (1) structural color applications, (2) tuning optical adsorption, and (3) barrier coatings. |
Thursday, March 9, 2023 5:12PM - 5:24PM |
W05.00010: Phase behavior of polymer-grafted nanoparticle blend films via thermal and solvent vapor annealing Akhtar Gul, Kshitij Sharma, Jirameth Transangpradit, Michael R Bockstaller, Krzystof Matyjaszewski, Alamgir Karim While chemically similar polymer-grafted nanoparticle (PGNPs) blends can offer enhanced material properties compared to their homopolymer analogs, such as in preventing film crack propagation, the phase behavior and mechanical behavior of chemically dissimilar PGNPs have not been explored. Generally, we expect this to depend on nanoparticle size(ro), polymer grafting density, brush segmental interactions, and polymer inorganic core interaction parameters. Both enthalpic and entropic (conformational and mixing) interactions between the polymer chains can play an essential role in the phase behavior of the PGNP blend system, while kinetics will determine their final domain or mixed state structure. As thermal annealing (TA) may be challenging to enable high mobility in large PGNP systems, we utilize alternate methods, such as solvent vapor annealing (SVA) and Direct immersion annealing (DIA), to process dissimilar binary PGNP systems of polymethyl methacrylate silica (PMMA-SiO2) and polystyrene acrylonitrile blend silica (PSAN-SiO2) (acrylonitrile content = 13%). Atomic force microscopy is used to characterize the surface topography and mechanical contrast of the thin films to identify phase behavior for different processing temperatures, film thickness, and annealing time. Results on kinetics and phase behavior of PGNP blends and their mechanical modulus by the SIEBIMM method will be discussed. |
Thursday, March 9, 2023 5:24PM - 5:36PM |
W05.00011: Importance of Polymer Ligand Conformation to Entropy-Driven Assembly of Nanoparticles within Block Copolymer Particles Meng Xu, Kang Hee Ku, Young Jun Lee, Jaeman Shin, Hongseok Yun, Bumjoon J Kim The conformation of polymer brushes can direct the nanostructures of hybrid materials as it affects the entropic interactions between grafted chains and matrix chains. Herein, we demonstrated the precise spatial alignment of polystyrene-grafted Au nanoparticles (Au@PS) within onion-like polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) block copolymer (BCP) particles depending on the parameters related to the conformation of PS ligands, including the ratio of PS block molecular weight (Mn) to PS ligand Mn (P/N), core size of Au@PS (r), and grafting density of PS ligands (σ). Change in any of the parameters drives dramatic morphological transitions of hybrid particles. PS ligands having low interfacial interactions with BCP chains were excluded from the BCP domains. In contrast, high interfacial interactions between Au@PS and BCP chains allowed the formation of Au@PS arrays within PS blocks. To evaluate the entropic interactions, a modified swelling ratio (P/NSDPB) is proposed by considering the ligands in the semi-dilute polymer brush (SDPB) regime as the only brushes available for interfacial interactions with BCPs. In addition, the effect of nanoparticle size was taken into account for a comprehensive understanding of the entropic interactions in the hybrid system. |
Thursday, March 9, 2023 5:36PM - 5:48PM |
W05.00012: Implicit Chain Particle Model for Polymer Grafted Nanoparticles Zhenghao Wu, Subhadeep Pal, Sinan Keten Matrix-free nanocomposites made from polymer grafted nanoparticles (PGN) represent a paradigm shift in materials science because they greatly improve nanoparticle dispersion and offer greater tunability over rheological and mechanical properties in comparison to neat polymers. Utilizing the full potential of PGNs requires a deeper understanding of how polymer graft length, density, and chemistry influence interfacial interactions between particles. There has been great progress in describing these effects with molecular dynamics (MD). However, the limitations of the length and time scales of MD make it prohibitively costly to study systems involving more than a few PGNs. Here, we address some of these challenges by proposing a new modeling paradigm for PGNs using a strain-energy mapping framework involving potential of mean force (PMF) calculations. In this approach, each nanoparticle is coarse-grained into a representative particle with chains treated implicitly, namely, the implicit chain particle model (ICPM). Using a chemistry-specific CG-MD model of PMMA as a testbed, we derive the effective interaction between particles arranged in a closed-packed lattice configuration by matching bulk dilation/compression strain energy densities. The strain-rate dependence of the mechanical work in ICPM is also discussed. Overall, the ICPM model increases the computational speed by approximately 5-6 orders of magnitude compared to the CG-MD models. This novel framework is foundational for particle-based simulations of PGNs and their blends and accelerates the understanding and predictions of emergent properties of PGN materials. |
Thursday, March 9, 2023 5:48PM - 6:00PM |
W05.00013: In situ observation of metal precipitation on metal oxide using polymer brushes as a template by X-ray absorption spectroscopy Maiko Nishibori, Kakeru Ninomiya, Akira Miyano, Kazutaka Kamitani, Kazuo Kato directly related to catalytic function and optical properties. In this study, we tried to deposit Pd on the TiO2 surface using a polymer brush on the substrate as a “template” without the adsorption of metal ions to the polymer. We also investigated the interaction of the substrate (TiO2), polymer (PMMA), and metal (Pd) by observing the reduction process using energy-dispersive X-ray absorption spectroscopy (DXAFS). The molecular weight and graft density of PMMA on the TiO2 were 22,600 and 0.26 /nm2, respectively. Pd deposition reaction was performed by mixing [PdCl4]2- aq. and PMMA modified TiO2 (PMMA-TiO2) or no treatment TiO2 (NT-TiO2) and photoreduction. Comparing the average grain size of Pd precipitated on the TiO2 surface, PMMA-TiO2 promoted grain growth of Pd more than NT-TiO2. Furthermore, the grain size distribution suggests that the polymer brush on TiO2 suppressed grain growth of Pd, indicating that the brush acted as a template. DXAFS measurements observed the Pd reduction behavior, and it was found that the reduction reaction proceeded with the presence of PMMA and TiO2 in the reaction system. The Pd chemical state at the beginning of the reduction reaction was changed by PMMA, forming a brush morphology, suggesting that the space created by the PMMA brush functions as a unique reaction field. |
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