Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session R56: Polymer Nanocomposites II: Functional ApplicationsFocus
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Sponsoring Units: DPOLY Chair: Praveen Agarwal, The Dow Chemical Company Room: LACC 515B |
Thursday, March 8, 2018 8:00AM - 8:12AM |
R56.00001: Effects of Morphology on the Mechanical Properties of Heterogeneous Polymer-grafted Nanoparticle Networks Tao Zhang, Badel Mbanga, Victor Yashin, Anna Balazs Using computational modeling, we examine how varying the arrangement of binary mixtures of polymer grafted nanoparticles (PGNs) in a network affects the mechanical properties of the composite. The free ends of the grafted chains on the PGNs contain reactive groups that can form labile bonds with reactive ends on nearby PGNs, and thereby form extensive networks. The two types of particles in the network differ in the strength of the labile bonds that they form with their neighbors, forming both relatively strong and weak interconnections. We examine the response of this dynamic network to tensile deformation when the binary PGNs are arranged in an alternating, layered structure or a random mixture. We determine the ultimate tensile properties (strength, toughness), the strain recovery and behavior under cyclic loading for samples with the layered and random architectures. We demonstrate that the layered structures display self-healing behavior and exhibit enhanced mechanical properties relative to the random system. Using our model, we can tune both the spatial and temporal characteristics of the hybrid material. Thus, the approach provides a useful tool for determining how to tailor these parameters to achieve superior mechanical behavior in PGN networks. |
Thursday, March 8, 2018 8:12AM - 8:24AM |
R56.00002: Role of the polydispersity of nanoparticle size, grafted chain length and grafting density on the self-assembly of polymer nanocomposites Nirmalya Bachhar, Sanat Kumar The self-assembly of polymer chain-grafted-nanoparticles in polymer matrix leads to the formation of different superstructures, e.g., well-dispersed particles, strings, and aggregates. However the effect of polydispersity of individual parameters, e.g., particle size, grafting density and chain length is not comprehensively understood. We show that these distributions lead to a variety of superstructures being formed in the sample, and that the polydispersity of superstructures formed in the same polymer matrix is governed by the inherent polydispersity of nanoparticle size and grafting density. Further, it is found that increasing the polydispersity of the length of the grafted chains leads to less aggregated structure based on a simple geometric parameter of particle to polymer size ratio. Thus, we conclude that the distribution of nanoparticle sizes is the most important variable in this context. |
Thursday, March 8, 2018 8:24AM - 8:36AM |
R56.00003: Nanocomposites Containing Aromatic Polymers with Bulky Pendant Groups and C60 for Gas Separation Applications Venkat Padmanabhan, Rimpa Chatterjee, Soumendu Bisoi, Susanta Banerjee Polymer nanocomposites have gained significant interest in the past few years as membranes for gas separation due to their outstanding set of physical properties. Currently, the permeability/selectivity relationship for membranes is limited by the Robeson line. Aromatic polymers containing bulky pendant groups in the side chains have shown to inhibit the close packing of polymer backbone resulting in higher free volume and permeability. Inclusion of fullerene particles further disrupt the packing and result in percolated free volume channels for efficient transport of gas molecules through the membrane. In this talk, we present molecular dynamics simulations of these polymer membranes and report how the fractional free volume (FFV), diffusivities of various gases, and selectivity/permeability relationship vary as a function of nanoparticle concentration. It is observed that the diffusion dominated gas transport through the FFV effectively increased the permeation property. The overall free volume, free volume distribution, morphological nature and accessible volume of the polymers play a significant role in affecting gas permeation. |
Thursday, March 8, 2018 8:36AM - 8:48AM |
R56.00004: Nanoparticle Reshaping in Polymer Nanocomposites: Quantifying the Effect of Polymer Mechanics on Gold Nanorod Surface Diffusion Dynamics William Kennedy, Vikas Varshney, Sarah Izor, Hilmar Koerner Thermal reshaping via surface diffusion is an important phenomenon in gold nanorod polymer composites. Observed reshaping dynamics at a given temperature depend strongly on the nanorod environment, as evidenced by observed exponential time constants in different systems ranging from seconds to days. We have measured the shape dependent extinction spectra in nanocomposites having different gold nanorod morphologies and different matrix mechanical properties. We show that a surface diffusion model is sufficient to explain the intial rate of shape transformation in all cases, but that the ultimate amount of reshaping depends on the matrix and the initial morphology of the nanorods. The interaction of grafted ligands with the surrounding matrix plays an important role in the thermal reshaping dynamics as well as the interpretation of the scattering spectra in these systems. |
Thursday, March 8, 2018 8:48AM - 9:00AM |
R56.00005: Structural and Molecular Transport Properties of Self-Assembled polymer grafted Nanoparticles Connor Bilchak, Hope Weinstein, Sanat Kumar, Brian Benicewicz, Yucheng Huang The use of polymer-grafted nanoparticles (NPs) for dispersing nanofiller in a polymer matrix has led to novel materials exhibiting improved mechanical and optical properties, though their applicability to molecular transport has remained unexplored. We focus here on spherical silica NPs (d=14nm) sparsely grafted with polystyrene (PS) chains in a PS matrix. By tuning the graft density and PS chain lengths, a variety of self-assembled structures can be formed and characterized through TEM imaging and Small-Angle X-ray Scattering (SAXS). The gas transport performance of the various hybrid materials, measured via Quartz Crystal Microbalance (QCM) and steady-state permeation experiments, show that the CO2 permeabilities do not obey conventional (i.e., Maxwell) theories for transport (despite the pure grafted NPs following prediction) and that the spatial distribution of the NPs in the self-assembled state has profound consequences on molecular transport properties. Additionally, high frequency mechanical measurements permitted by the QCM indicate variations in mechanical performance in these materials. The ability to rationally design polymer composites with tunable transport properties using NP morphological control thus represents a new path forward for advanced membrane design |
Thursday, March 8, 2018 9:00AM - 9:12AM |
R56.00006: Plasmonic Nanoparticles Meet Polymers: Revelation of the Polymer Brush Formation Mechanism Guoliang Liu We will present our recent progress on the utilization of plasmonic nanoparticles in polymer sensing. Currently the synthesis of plasmonic nanoparticles for sensing mostly focuses on the shape because it is believed that nanoparticles with sharp tips provide higher sensitivities than those without. By analyzing the sensitivities of more than 74 types of nanoparticles of various shapes, sizes, and compositions, we found that the correlation between shape and sensitivity is much weaker than that between aspect ratio and sensitivity. Among many parameters including size, shape, composition, aspect ratio, cross-sectional area, and initial plasmonic resonance frequency, the aspect ratio is the key parameter that controls the nanoparticle sensitivity. Other parameters have much less influence on the nanoparticle sensitivity to refractive index changes. Based on this finding, we selected Ag nanodisks as sensors to probe the kinetics of polymer brush formation. Unitizing the plasmonic properties of Ag nanodisks, we demonstrated in situ the three-regime kinetics of polymer brush grafting process, and importantly, for the first time we revealed the cause of a latent regime during the polymer brush grafting process, which has been a long-lasting puzzle in the field of polymer brush. |
Thursday, March 8, 2018 9:12AM - 9:48AM |
R56.00007: Processing and Performance of Large-Area Polymer-Grafted Nanoparticle Assemblies Invited Speaker: Richard Vaia Polymer nanocomposites (PNCs) are a blend of inorganic nanoparticles (NPs) and polymer, where the nanoscale morphology, increased number density of filler, and prominence of internal interfaces may yield improved thermal, mechanical and electrical performance with respect to classic filled or composite systems. These enhancements have provided numerous solutions, ranging from coatings to packaging. For many emerging technologies however, these gains are insufficient; thermodynamics, processing requirements, and interface functionalization pose practical limits to blended PNCs. Here in, we will discuss an alternative concept - assemblies of polymer grafted nanoparticles (PGNs). PGN and their assemblies present intriguing parallels with other mesoscale ordered macromolecules, such as hard-soft blocks, stars, combs and semi-crystalline polymers. The tunability of the hard-soft architecture via the size and shape of the nanoparticle core and the areal density and molecular weight of the polymer grafts leads to chimeric characteristics; and thus opportunities to design high inorganic fraction systems with ordered morphology while retaining the necessary processibility to create high-performance films and fibers. Understanding how solution processing and the architecture of the polymer canopy mediates the intervening polymer network has enabled fabrication of large scale, highly ordered monolayer films from PGN inks within seconds using simple flow coating. The PGN assemblies demonstrate novel optical and dielectric properties as well as enhanced toughness and thermal integrity relative to linear chain or blended NP analogs. |
(Author Not Attending)
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R56.00008: Light-Enabled Reversible Self-Assembly and Tunable Optical Properties of Photoresponsive Polymers-Ligated Nanoparticles Zhiqun Lin By judiciously design amphiphilic star-like diblock copolymers comprising inner hydrophilic blocks and outer hydrophobic photoresponsive blocks as nanoreactors, monodisperse plasmonic NPs intimately and permanently capped with photoresponsive polymers were prepared. The size and shape of hairy NPs can be precisely tailored by modulating the length of inner hydrophilic block of star-like diblock copolymers. The perpetual anchoring of photoresponsive polymers on the NP surface renders the attractive feature of self-assembly and disassembly of NPs on demand using light of different wavelengths, as revealed by tunable surface-plasmon resonance absorption of NPs and the reversible transformation of NPs between their dispersed and aggregated states. |
Thursday, March 8, 2018 10:00AM - 10:12AM |
R56.00009: Melt Dynamics of Grafted Nanoparticles Ramanan Krishnamoorti
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Thursday, March 8, 2018 10:12AM - 10:24AM |
R56.00010: Role of Chemical Heterogeneity in Bound Layers on the Mechanical Properties of Polymer Nanocomposites Siyang Yang, Pinar Akcora We recently showed that chemical heterogeneity of interfacial layers around particles governs the mechanical properties of polymer nanocomposites. Poly(vinyl acetate) (PVAc) adsorbed silica nanoparticles in two different matrices, poly(ethylene oxide) (PEO) and poly(methyl acrylate) (PMA) matrices are investigated in rheology and small-angle X-ray scattering. Dynamic coupling that is governed by entanglements and interactions between two polymers is enhanced with the short PMA matrix and the long PVAc adsorbed chains on particles. In the PEO system, short adsorbed chains of PVAc reinforced the composite more than the other chain lengths. Our results show that miscibility and attractions between adsorbed and matrix chains in interfacial layers lead to their unusual reinforcement. The results suggest that packing of chains at interface layers may contribute to the reinforcement effect. Composites under large oscillatory deformations are thus examined to reveal the enhancement of mixing, molecular attractions and density of interfaces between adsorbed and matrix chains under shear. |
Thursday, March 8, 2018 10:24AM - 10:36AM |
R56.00011: Manipulating 3-D Nanoparticle Assembly to Tune Optical Properties of Lamellar Nanocomposite Thin Films Jingyu Huang, Xiangfan Chen, Peter Bai, Cheng Sun, Ting Xu Well-defined metal nanoparticles (NPs) assemblies exhibiting unique collective optical properties are promising candidates for metamaterials. Tailoring the coupling between the collective electron oscillations confined within individual NPs opens up a new way for comprehensive manipulation of light at nanoscale. The current challenge is how to rapidly fabricate large-scale hierarchical NP assemblies while maintaining precise control of inter-particle coupling in three-dimension (3-D). Here, we report a method to rapidly fabricate 3-D NP assemblies in lamellar supramolecular thin films by solvent vapor annealing and fast solvent removal, which efficiently decrease the lamellar periodicity and hence promotes strong coupling of the induced particle plasmon resonance. We found that films compromising 3-D array of 12 nm Au NPs exhibit pronounced optical anisotropy due to the presence of strong plasmonic coupling, which is in clear contrast to the films with 3 nm Au NPs featuring trivial plasmon coupling. This work presented an approach for scalable nanomanufacturing of optical metamaterials that fully exploiting 3-D coupling phenomena. |
Thursday, March 8, 2018 10:36AM - 10:48AM |
R56.00012: Bioinspired Mineralization in Hydrogels for Sustainable Applications Abigail Regitsky, Bavand Keshavarz, Sungjin Kim, Seth Cazzell, Gareth McKinley, Niels Holten-Andersen Biominerals have been widely studied due to their unique mechanical properties, afforded by their inorganic-organic composite structure and well-controlled growth in macromolecular environments. More recently, growing concerns over climate change and environmental sustainability and the emerging relevance of green chemistry make biomineralization an even more attractive process to study. Here, we focus on the earlier stages of mineral nucleation and growth, where the organic, hydrogel-like matrix dominates the bulk of the material and the mineral is distributed throughout the matrix as nano- and/or microparticles. The phase, morphology, and size of the particles can be controlled using the choice of the hydrogel, functional moieties on the gel polymer backbone or ends, and soluble additives. Depending on the choice of organic matrix and inorganic mineral, the matrix can be dissolved to leave highly uniform particles with tailored properties for a variety of industrial applications, or the matrix can be left intact, creating a hydrogel-mineral composite with improved mechanical properties through organic-inorganic interfacial interactions or additional functionality, such as magnetic properties. |
Thursday, March 8, 2018 10:48AM - 11:00AM |
R56.00013: Tunable Interactions of Polymer-Plasmonic Nanoparticle Composites with Visible and Near-Infrared Light Assad Ullah Khan, Yichen Guo, Guoliang Liu Plasmonic nanoparticles absorb or scatter a particular wavelength of light corresponding to their localized surface plasmon resonance (LSPR). In this work we present the utilization of Ag nanoplates in polymer composites to modulate light across the visible and NIR range. The nanoparticle-polymer nanocomposites were fabricated through either layer-by-layer assembly (LbL) or random distribution of grafted nanoparticles in polymer matrices. We studied two independent types of nanoparticle-polymer nanocomposites. Optical measurements revealed controlled transmittance and reflectance at the resonance frequency of both random and oriented polymer nanocomposites. In addition, we tuned the optical properties by controlling the density of the nanoparticles and the number of nanoparticle layers in the polymer composites. |
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