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 Y05: Hybrid and Multicomponent Polymer Materials Containing Nanoparticles IIFocus
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Sponsoring Units: DPOLY Chair: Shiwang Cheng, Michigan State University Room: Room 128 |
Friday, March 10, 2023 8:00AM - 8:12AM |
Y05.00001: Can interparticle contacts in polymer nanocomposites be tuned via photothermal heating of the particle? Laura Clarke, Erin Crites, Jason Bochinski Nanocomposite processing presents a paradox: strong particle-matrix interactions facilitate dispersion, thus minimizing the particle doping level needed to form a percolating network. However, they ultimately diminish composite properties, particularly electrical conductivity, as current must pass through insulating matrix caught between conducting particles. Ideally, particle-matrix interactions would be strong during fabrication to maximize dispersion and then altered to favor particle-particle contact and expel inter-particle matrix after solidification. We present results utilizing photothermal heating of multi-walled carbon nanotubes (CNT) to explore this paradigm. Photothermal heating is a process whereby light is absorbed by nanoparticles resulting in localized heat: illuminating a composite results in significant temperature increase around each particle (and particle-particle junctions) while regions far from the particles remain cool. We discuss the effects of photothermal treatment of CNT-polymethylmethacrylate composites during fabrication (casting from solvent) and in solid form with and without applied current with the goal of understanding how the particle-matrix interaction can be manipulated with heat. |
Friday, March 10, 2023 8:12AM - 8:24AM |
Y05.00002: Hybrid Nanomanufacturing of Gas-controlled Electrospin/spray for Breathable Composite PPE Jay H Park, Taiyo H Yamaguchi, Yrvanie Joseph The ever-increasing need for lightweight, high performance personal protective equipment (PPE) is seen across multiple sectors such as manufacturers, defense, and medical. While functional membranes composed nanocomposites had existed for decades, the biggest challenge for the next-gen PPE has been to meet the textile/comfort requirements while meeting the metrics of solid/liquid/gas protection. Nonwoven nanofibers field the unique capability of being breathable with a large surface area with tiny pores to protect oneself from chemical and biological hazards. Herein is an investigation of parallel electrospinning polyvinyl alcohol (PVA) or polyacrylonitrile (PAN) fibers spun in conjunction with electrospraying metal-organic frameworks (MOF) nano-microparticles that provides both breathable scaffold filters with highly reactive MOF sites with mass wt.% loading as high as 70-80 wt% of the composite. A novel gas-controlled electrospinning/electrospray has been implemented which enable uniform deposition of the composite membrane without use of any binder. Processing parameters and its implication on loading, morphology, and throughput is discussed. The processing-structure-property relationships of the said method are examined with textile functionalities in mind, such as air permeability, water vapor transmission rate, and its protection and gas-soprtion capabilities such as air particle filtration. |
Friday, March 10, 2023 8:24AM - 8:36AM |
Y05.00003: Crowded and Bimodal Size Nanoparticle Diffusion in Polymer Melts by ToF-SIMS Kaitlin Wang, Russell J Composto, Karen I Winey Nanoparticle (NP) diffusion in polymer nanocomposites (PNCs) is an important aspect in self-healing materials, drug delivery, and processing. NP size relative to matrix chains and NP loading are both well-studied factors that affect NP diffusion in polymer melts; however, methods like dynamic light scattering or single particle tracking are unable to access crowded NP regimes. Using time-of-flight secondary ion mass spectroscopy (ToF-SIMS), we investigate crowded and mixed nanoparticle systems in a poly(2-vinylpyridine) (P2VP) melt system on micron length scales. ToF-SIMS was used to measure cross-sectioned trilayer polymer-PNC-polymer samples to obtain 1D NP concentration profiles that are fit to obtain diffusion coefficients. We measure alumina and silica NPs of distinct sizes to obtain diffusion coefficients in low and high molecular weights matrices separately, then simultaneously in mixed-NP PNCs. With NPs of size < Rg and > Rg within the same PNC, two NP diffusion mechanisms are expected simultaneously, and we observe the effect of NP size and loading. This work provides insight into NP diffusion mechanisms in crowded and mixed-NP nanocomposites using the unique capabilities of ToF-SIMS. |
Friday, March 10, 2023 8:36AM - 8:48AM |
Y05.00004: Curing condition influences the piezoresistivity of MWNT/epoxy nanocomposites Fangxin Zou, Ting-yui Wong, Tao Yu Non-monotonic electrical resistance change vs. tensile strain relationships have been observed in MWNT/epoxy nanocomposites, but the mechanism is not fully understood. While previous studies mostly investigated the effect of nanofiller content, this work evaluates the influence of curing condition. The results of electromechanical experiments demonstrate that the monotony of the piezoresistivity of a MWNT/epoxy nanocomposite could be enhanced by employing a higher curing temperature. Moreover, atomic force microscopy and in situ near infrared spectrometry were used to probe the curing kinetics and the curing-dependent molecular structures of epoxy matrices, showing that both rigid domains and compliant domains could develop inside an epoxy matrix during curing and the level of spatial heterogeneity would depend on the curing temperature. Therefore, it is proposed that when cured under a different temperature, an epoxy matrix would exhibit a different level of spatial heterogeneity in molecular structure and hence in mechanical properties, causing the MWNT network inside the matrix to undergo a different movement trend under tension. This work establishes the causal relationship between curing condition and the piezoresistivity of MWNT/epoxy nanocomposites through considering the contribution of the molecular structures of polymer matrices. |
Friday, March 10, 2023 8:48AM - 9:00AM |
Y05.00005: Strong and Robust Composites Based on Recycled Polyurethane Products Mohammad Galadari, Divya Iyer, Fernaldy Wirawan, Vanessa Huaco, Ricardo Martinez, Michael Gallagher, Laurent Pilon, Kanji Ono, Dante Simonetti, Guarav Sant, Samanvaya Srivastava Chemical recycling of polyurethane is typically pursued through glycolysis, hydrolysis, or acidolysis. Polyols obtained from these processes exhibit high -OH values and are used as only a partial replacement to virgin polyols in the production of polyurethane, owing to a lack of control over the chemistry of these recycled polyols. In this presentation, we demonstrate an alternative approach to utilize recycled polyols, obtained by glycolysis of industrial scrap foam, to fabricate strong and robust organic/inorganic composites suitable for structural applications. These organic/inorganic composites, consisting of recycled polyols, naturally occurring aluminosilicate minerals, and organic binders, possess enhanced flexural properties (strength and strain capacity) as compared to ordinary Portland cement (OPC). A correlation between the chemical composition (type of linker, polyol content, type and content of inorganic particles), microstructure, and flexural properties will be discussed. Finally, we will demonstrate that optimization of the composition, curing temperatures, and processing conditions can help tune the properties and applicability of these organic/inorganic composites. |
Friday, March 10, 2023 9:00AM - 9:12AM |
Y05.00006: Damping Characteristics of Polyurea Nanocomposites Over an Extreme Range of Strain Rates Christine C Roberts, Jessica W Kopatz, Brian P Fox, Cody Kunka, Elizabeth M Jones, Chad A McCoy, Shawn D Pautz, Rekha R Rao, Christopher R Riley, Brett Sanborn, Justin Wagner Polyurea nanocomposites are used as encapsulants and coatings to increase durability, corrosion, or impact resistance of surfaces. Undoped polyurea has exceptional toughness and impact resistance, derived from a phase-separated hard segment/soft segment microstructure and hydrogen bonding. Here, we measure the impact of nanoparticle filler concentration to enhance polyurea dynamic mechanical properties. Surface modification of the nanoparticles is optimized to promote homogeneous particle dispersion, maximum particle volume fraction, and particle-matrix adhesion. Particle-matrix compatibility significantly affects the ultimate tensile stress for the nanocomposites. The mechanical performance of polyurea nanocomposites is contrasted with that of unfilled polyurea via dynamic mechanical analysis, Hopkinson bar, and shock tube testing, demonstrating the ability of polyurea nanocomposites to damp vibrational energies over an extreme range of strain rates (0.1 – 5,000 s-1). In shock tube samples, reduction of the total deflection (75%) and deflection rate (40%) of aluminum plates is observed with nanocomposite coatings. Finally, highest strain rate insults were imposed by a thermomechanical shock in the Sandia National Laboratories SPHINX electron beam and Z-machine X-ray pulsed power facilities, where the damping of nanocomposites was measured to strain rates of 106 s-1. Effects of particle size, concentration, and aggregation level are discussed on the ability of the composites to damp shock, as well as the effect of the radiative environments on the polymer microstructure, composite modulus, and chemical changes in the material. This work is a comprehensive examination of the role of nanoparticles in shock mitigation across deformation timescales for these polymer nanocomposites. |
Friday, March 10, 2023 9:12AM - 9:48AM |
Y05.00007: Recyclable Polymer Network Nanocomposites and Composites via Dynamic Covalent Bonds: Achieving Full Cross-link Density and Other Property Recovery after Reprocessing Invited Speaker: John M Torkelson The development of covalent adaptable networks, sometimes called vitrimers, holds promise for overcoming long-standing recycling and polymer circularity issues associated with conventional, permanently cross-linked thermosets which cannot be recycled for high-value use. It is also important to demonstrate that properties of reprocessable networks can be optimized to meet ongoing demands for high-performance materials. We have designed several network nanocomposites and composites that demonstrate that such performance demands can be met while maintaining polymer circularity and contributing to sustainability. In one example, we used a strategy based on nitroxide-mediated polymerization to synthesize reprocessable networks and network composites containing alkoxyamine dynamic bonds. The networks, including those synthesized from lab-grade polybutadiene and industrial-grade natural rubber/carbon black composites, exhibit full cross-link density recovery and essentially no creep at 80 °C, where alkoxyamine cross-links are nearly static, after multiple molding cycles at 140/160 °C, where alkoxyamine cross-links are dynamic. The ability to “turn on” and “arrest” dynamic chemistry over a relatively narrow temperature (T) window is due to the relatively high activation energy (∼120 kJ/mol) and thus strong T-dependence of the alkoxyamine dissociation reaction. In a second example, we fabricated reprocessable polyhydroxyurethane (PHU) network nanocomposites reinforced with reactive polyhedral oligomeric silsesquioxanes (POSS). With functionalized POSS as a fraction of the cross-linkers, the PHU–POSS network nanocomposites exhibit enhanced storage modulus at the rubbery plateau region relative to neat PHU network. With up to 10 wt% POSS, the network composites undergo melt-state reprocessing at 140 °C with 100% cross-link density recovery. The hydroxyurethane dynamic chemistry leads to excellent creep resistance at T up to 90 °C and is unaffected by reactive incorporation of POSS. This study demonstrates the effectiveness of POSS as nanofillers for designing high-performance, organic−inorganic dynamic PHU networks with excellent reprocessability. We will also describe situations where the presence of nanofillers can lead to incomplete property recovery after reprocessing. |
Friday, March 10, 2023 9:48AM - 10:00AM |
Y05.00008: Bound Polymer Layer induced Mechanical Enhancement in Polymer Nanocomposites Tae Yeon Kong, So Youn Kim The superior properties of polymer nanocomposites (PNCs) is believed to originate from adsorbed polymers around nanoparticles, particularly from the interfacial layer exhibiting slower segmental dynamics than bulk polymers. Meanwhile, the bound polymer layer created by the entire adsorbed polymer has distinguished chain conformations compared to bulk polymers; however, received less attentions than the dynamically defined interface layer. |
Friday, March 10, 2023 10:00AM - 10:12AM |
Y05.00009: Quantifying Localized Stresses in a Single Fiber Reinforced Polymer Composite Utilizing Mechanophores Nazmul Haque, Chelsea S Davis Understanding the onset of failure in fiber-reinforced polymer composites is critical for increasing their service life. However, the instantaneous nature of fracture makes it difficult to obtain real-time experimental data on the damaged regions. A compounding challenge is the lack of experimental tools to sense and quantify localized stress and distribution within the matrix during fracture. Visual feedback from mechanoresponsive force probes (mechanophores) employed within the system can directly monitor stress buildup. In this work, we employed spiropyran (SP) mechanophore within polydimethylsiloxane (PDMS) matrix to visualize the stress localization during fracture in a single fiber-reinforced system. The SP mechanophore transitions from a fluorescent inactive state to an active state (merocyanine) via isomerization under force and strain. One single fiber within the matrix was used to simplify the composite model, demonstrating the fundamental failure modes prevalent in traditional fiber-reinforced composites during uniaxial tensile testing along the fiber direction. At the interface, the tensile load translates from matrix to fiber via shear stress. Confocal microscopy was used to visualize mechanophore activation and quantify the fluorescence intensity. The uniaxial tensile test of dogbone samples showed a gradual stress buildup in the matrix from the fiber/matrix interface. The results indicated that these mechanoresponsive molecules could be promising for visualizing real-time stress distribution and designing high-performance composites. |
Friday, March 10, 2023 10:12AM - 10:24AM |
Y05.00010: Using Field Theoretic Simulations to Study the Thermodynamics of Core-Shell Bottlebrush Copolymers Nanocomposites Christian Tabedzki, Robert A Riggleman Polymer nanocomposites (PNCs), polymer based systems imbued with property modifying nanoparticles, ranging from enhanced mechanical stiffness and improved electron transport to enhanced thermal conductivity, are of great interest in a wide range of applications. The characteristics of PNCs can be tailored via nanoparticles design (composition, radius, shape, etc.) and polymer matrix design (architecture, composition, molecular weight, etc.). Novel architectures like core-shell bottlebrush copolymers (csBBs), a class of polymers with long backbone and short diblock chains, are of particular interest for PNC design due to their low entanglement density and large equilibrium grain sizes. In this work, we combine thermodynamic integration with theoretically-informed Langevin dynamics (TILD), a field-theoretic simulation technique, to investigate the solubility of nanoparticles in block copolymers with varied architectures. We examine how the system features (NP particle size, polymer architecture, degree of polymerization) affect the excess chemical potential and solubility of the nanoparticles. Our results provide a foundation for understanding the effect of polymer architecture on PNCs. |
Friday, March 10, 2023 10:24AM - 10:36AM |
Y05.00011: Development of Polyurethane/r-GO Nanocomposites with Improved Self-healing Properties Kiriaki Chrissopoulou, Evangelia Giannakaki, Kosmas Giannaris, Minas Stylianakis, Spiros H Anastasiadis In recent years, self-healing coatings have been the subject of increasing research interest due to their ability to self-repair local damages caused by external forces. Polymeric materials comprise one of the most promising materials to use towards this direction. At the same time, incorporation of nanoadditives within a polymeric matrix is a common strategy to improve their mechanical, thermal and self-healing properties. In the current work, reduced graphene oxide (rGO) was incorporated within a waterborne polyurethane dispersion to develop nanocomposites in different compositions and investigate its effect on the self-healing properties. The polyurethane was based on a polycarbonate polyol whereas graphene oxide (GO) was synthesized via a modified Hummers method from graphite; subsequent reduction using hydroiodic acid (HI) as a reducing agent produced the rGO used. The presence of rGO enhanced the self-healing of the polyurethane coatings with a healing rate much higher compared to that of the pure polymer, as confirmed by microscopic techniques. This was mainly due to better heat dissipation where the high heat conductivity of rGO allowed for the improvement of the self-healing ability with the incorporation of just a small amount of the additive. The effect of the presence of rGO on the mechanical properties of the nanocomposites after healing was investigated, as well. |
Friday, March 10, 2023 10:36AM - 10:48AM |
Y05.00012: Elucidating the impact of lignin molecular weight and composition on the network structure and transport properties of lignin-based hydrogel composites Keturah Bethel, Graham Tindall, Mark Thies, Eric M Davis Given its biodegradability, antimicrobial properties, chemical activity, and economic appeal, lignin has proven to be a favorable choice for use in the fabrication of sustainable soft composites. However, the heterogenous nature of lignin obstructs our ability to accurately understand how the presence of lignin alters the network structure and ultimately the mechanical and transport properties of these soft composites. To address this gap in our knowledge, a collection of physically crosslinked lignin–poly(vinyl alcohol) (PVA; MW ~133 kDa) soft composites were synthesized using the freeze-thaw method. Specifically, soft composites containing 60 mass % of either BioChoice lignin (raw/feed lignin; MW ~ 20 kDa) or fractionated lignin of various MWs (ranging from ~6 kDa to ~160 kDa) were fabricated. The synthesis of these hydrogels with varying lignin MWs provides a basis of comparison, allowing the advantages of the fractionated lignin to be highlighted. To elucidate how the mesh size of the lignin-based hydrogels can be modulated by these changes, the transport properties have been thoroughly characterized. Firstly, the influence on the mesh size was gauged through performing drug loading studies utilizing bovine serum albumin as the model drug. Secondly, the permeability of methylene blue within the resulting network structure was examined. Lastly, the diffusion coefficient of water has been extracted for these systems by applying poroelastic relaxation indentation. The results from this investigation indicated that the network structure and transport properties were influenced with varying molecular weight and dispersity of lignin.
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