Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session V03: Highly Loaded and Morphologically Enhanced Polymer NanocompositesInvited Live
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Sponsoring Units: DPOLY Chair: Zahra Fakhraai, University of Pennsylvania |
Thursday, March 18, 2021 3:00PM - 3:36PM Live |
V03.00001: Design of Complex Biomimetic Nanocomposites: Graph Theory Invited Speaker: Nicholas Kotov Materials that are multifunctional, structurally versatile, and resource conscious, represent the critical bottlenecks of nearly all modern technologies -- the qualities typical of components of many living tissues. Although the notion of Nature-inspired materials is known for hundreds of years, the true challenges for transition from superficial replication some geometrical parameters to property-driven biomimetic materials design become fully appreciated only lately. Perhaps, the central one among these challenges is the multiplicity of scales enumeration of the complex structure of the biomimetic composites in a manner suitable for the property optimization. |
Thursday, March 18, 2021 3:36PM - 4:12PM Live |
V03.00002: Polymer Processing at Liquid Crystal-Air Interfaces Invited Speaker: Laura Bradley Fluid interfaces are unique environments for materials processing because, as inherently open systems, they promote dynamic transport from adjoining phases and offer anisotropic structures that give rise to strong directional interactions during assembly. Liquid crystal interfaces add further prospects for producing materials with directed ordering or anisotropic morphology. For example, colloids assembled at liquid crystal-air and liquid crystal-water interfaces have been demonstrated to form a spectrum of superstructures from chains to hexagonal lattices. In this talk, we demonstrate liquid crystal-mediated synthesis and assembly of polymer colloids at liquid crystal-air interfaces. The polymer colloids are produced by polymerization of a methacrylate monomer in a non-reactive liquid crystal. We examine the mechanisms governing the simultaneous colloid growth and assembly. Our results outline design rules to control the nucleation and growth of morphologically enhanced polymer composites by leveraging interfacial phenomena in soft matter. |
Thursday, March 18, 2021 4:12PM - 4:48PM Live |
V03.00003: Driving and manipulating polymer degradation in nanocomposites via photothermal heating of the particle Invited Speaker: Laura Clarke We are interested in thermally-driving chemical reactions in small volumes within a solid material, where diffusion of reactants and products are limited. Such experiments are achieved by photothermally heating metal nanoparticles incorporated within a polymer, which creates significant heat generation at the particle and an inhomogeneous steady state temperature distribution across the solid. Specifically, polymer far from any particle is cool while in contrast, local regions surrounding a particle experience temperatures up to few 100s deg. C. Utilizing polymer degradation as a test reaction creates a detectable product as a permanent record of the temperature profile and, if localized, forms defects which dramatically alter mechanical properties. In general, manipulating the connection between the fraction of chemical degradation and mechanical strength as an object deteriorates is important for plastic waste management where microfragmentation may either be harmful or beneficial depending on the remediation strategy. In addition, waste-to-carbon strategies may benefit from confinement. Polyethylcyanoacrylate (PECA) degrades by depolymerizing and in confinement the monomer will repolymerize to form oligomers. Photothermal heating of PECA exhibits heterogeneous degradation, including defect formation and synthesis of a carbonaceous by-product localized around each particle. In contrast, polyethylene (PE) degrades via thermo-oxidative processes that rely on the presence of oxygen and pre-existing defects in addition to heat; consequently, photothermal heating of PE demonstrates homogeneous degradation due to the distributed nature of the reaction pathway. |
Thursday, March 18, 2021 4:48PM - 5:24PM Live |
V03.00004: Ideas for Creating Impact Resistant Polymeric Materials by Tuning Molecular Topology Invited Speaker: Sinan Keten Biological materials employ diverse strategies for maintaining robustness against extreme mechanical environments, which often originate from clever molecular interfaces and microstructures. In this talk, I will summarize recent advances in computational design of new polymeric materials that make use of nanoscale topologies that result in improved mechanical properties. I will first present physics-based and data-driven approaches that we developed to describe molecular and mesoscale mechanics of polymer thin films and nanocomposites. Following this, I will present three distinct strategies for achieving impact tolerance in soft materials. The first strategy takes inspiration from helicoidal, imbricated Bouligand microstructures found in natural shells and armor materials, which results in superior impact response. The second strategy involves the use of star polymers and polymer grafted nanoparticles to improve diametric mechanical properties such as modulus and toughness,as well as the time-dependence of the mechanical response. The final strategy involves creating nanoparticle interfaces that take inspiration from catch bonds in biological adhesion proteins, which results in molecular seat-belt type interfaces that self-strengthen at high strain rates, in a way similar to shear-thickening fluids. I will conclude with some thoughts on how to translate these theoretical findings to new material concepts that could be explored further with synergistic experiments and simulations. |
Thursday, March 18, 2021 5:24PM - 6:00PM Live |
V03.00005: Infiltration of polymers into nanoparticle packings to produce highly loaded nanocomposites Invited Speaker: Daeyeon Lee Conventional methods of nanocomposite fabrication involve mixing and dispersing nanoparticles into a polymer matrix, making it challenging to produce composites with extremely high volume fractions (> 50 vol%) of nanoparticles. Recently our group has shown that such nanocomposites in the forms of films and membranes can be produced by capillary rise infiltration (CaRI) and solvent-driven infiltration of polymer (SIP). CaRI induces imbibition of polymer into the interstices of the nanoparticle packing via capillarity. In SIP, polymer infiltration is induced by exposing a bilayer of polymer and nanoparticle, which induces capillary condensation of the solvent in the interstitial voids of the nanoparticle packing and subsequent plasticization of polymer, leading to polymer infiltration into the solvent-filled interstices of the nanoparticle packing. While these methods provide powerful ways to produce highly loaded nanocomposites, they also provide a rich platform to study the behavior of polymers under extreme nanoconfinement. The chain dimension of the polymer, which depends on its molecular weight, can be comparable to or greater than the average pore size of the nanoparticle packing. In this talk, I will share our current understanding of the transport phenomena of polymers under such nanoconfinement using a combination of experimental and computational approaches. I will show that the dynamics of CaRI and SIP depends strongly on the confinement ratio as well as the molecular weight of the polymer. In particular, the effective viscosity of the polymer can decrease or increase depending on the extent of confinement and the molecular weight of the polymer. We also show that the structure and properties of the resulting nanocomposites also depend strongly on the processing parameters and the molecular weight of the polymer. |
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