Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session P46: Polymer Nanocomposites I |
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Sponsoring Units: DPOLY Chair: Pinar Akcora, Stevens Inst of Tech Room: LACC 506 |
Wednesday, March 7, 2018 2:30PM - 2:42PM |
P46.00001: Locating Graphene Oxide Derivatives at Low Loadings in Fiber Reinforced Polymer Composites using Raman Spectroscopy Qi An, Amber McCreary, Aaron Forster, Angela Hight Walker Incorporating graphene oxide (GO) nanofillers into polymers is a viable technique to improve mechanical properties at very small loadings. The addition of as little as 0.04 % by mass of surface modified GO in unsaturated polyester resin (UPR) can increase fracture toughness by as much as 50 % without lowering other mechanical properties. Rapid characterization of the nanofiller dispersion is crucial since property enhancements are strongly correlated to a uniform distribution of filler. This has proven difficult for high aspect ratio nanofillers in a polymer composite, and is almost impossible for fiber reinforced composites when the mass fraction of nanofiller is below 1 % by mass. Micro-Raman spectroscopy provides rapid, detailed, non-destructive measurements, and is a powerful technique to qualitatively identify nanoscale carbon-based materials. In this work, modified GO particles are located in an UPR matrix at 0.04 % by mass via spatial mappings of Raman spectra. The non-homogenous dispersion of the GO is clear in these mappings and likely enables the detection. This technique is also extended to composites reinforced with glass fibers where we measure GO particles near fiber interfaces. This robust work provides a significant advancement for guiding large scale production. |
Wednesday, March 7, 2018 2:42PM - 2:54PM |
P46.00002: Supramolecular Processing of Carbon Nanotubes and Polymers using a Non-volatile Organic Eutectic Liquid Chae Bin Kim, Ki-Beom Jeong, Beom Joo Yang, Seoung-Ki Lee, Chiyoung Park Carbon nanotube (CNTs) is a promising filler material for flexible electronics due to its high intrinsic carrier mobility, conductivity, mechanical flexibility, and etc. Despite the widespread success in a variety of applications using CNTs, however, making polymer–CNTs composites still requires long and tedious steps including dispersion of CNTs using a toxic and volatile organic solvent followed by the solvent removal. To this end, in this presentation, we report a facile, cost-competitive, and scalable method for producing flexible, conductive, and healable polymer-CNTs composites in the absence of a toxic, volatile organic solvent. We found a supramolecular, non-volatile eutectic liquid (EL), consisting of diphenylamine and benzophenone, can not only dissolve many commodity polymers but also form bucky gels with CNTs upon mixing. In order to take these advantages, polymer-CNTs composites were produced via one-pot melt-blending the EL and CNTs with a model thermoplastic elastomer, poly(styrene-b-butadiene-b-styrene). The resulting composite behaves as a highly sensitive, healable electromechanical sensor that can even measure blood pulsation on the human wrist. |
Wednesday, March 7, 2018 2:54PM - 3:06PM |
P46.00003: Jointed Capsule Model of Carbon Nanotubes and Its Applications in Polymer Nanocomposites Shengfeng Cheng, Ralph Romero Bead-spring models of polymer chains have been widely adopted to study mechanical and thermal properties of polymers. For nanocomposites containing carbon nanotubes (CNTs), it is thus desirable to develop similar models for CNTs. However, a bead-spring representation of a CNT suffers from the corrugation nature of a bead-spring chain, which makes the model incapable of correctly capturing the load transfer, friction, and adhesion at the interface between the CNT and other components in the nanocomposite. To overcome the corrugation issue, we have developed a jointed capsule model of CNTs in which each bond connecting two neighboring beads in a usual bead-spring chain is replaced by a cylinder with a diameter equal to the bead diameter. Each segment thus appears as a capsule. We have confirmed that in the jointed capsule model the potential experienced by a bead sliding over the surface of a CNT is smooth and does not show corrugation any more. We use the jointed capsule model to study the adhesion and friction between CNTs and the mechanical properties of nanocomposites consisting of a polymer matrix with dispersed CNTs and/or CNT bundles. |
Wednesday, March 7, 2018 3:06PM - 3:18PM |
P46.00004: Effect of nodal density in three-dimensional cellular structure of CNT- polymer on mechanical and viscoelastic properties RITUPARNA GHOSH, Abha Misra Cellular foams are high on demand due to their viscoelastic nature applicable for diverse engineering and bio-medical fields. Among the wide range of engineered cellular foams, carbon nanotube (CNT) cellular structure has been extensively used as nano-scale building block at macroscopic scale for their extraordinary mechanical strength, flexibility along with high electrical, thermal and viscoelastic properties. We designed and fabricated a novel CNT-polymer based porous architecture that demonstrated a unique microstructure dependent mechanical and viscoelastic properties. Controlled nodal density in the CNT architecture has shown a great dependence on viscoelasticity characteristics of the foam. Higher nodal density resulted in an increase in mechanical properties e.g. peak stress, energy absorption, rate of deformation. An optimum nodal density induces highest degree of viscoelasticity and beyond that it reduces due to agglomeration in CNT attributed to the van der Waals force. A systematic compressive behaviour is evaluated to elucidate the controlled stiffness and viscoelasticity of the cellular structure. |
Wednesday, March 7, 2018 3:18PM - 3:30PM |
P46.00005: Conductivity and Shielding Ability of Multicomponent Nanocomposites Pouyan Karimi, Morteza Saeidi-Javash, Martin Ostoja-Starzewski, Jianming Jin Conductive polymer nanocomposites have been developed as an interesting class of materials due to their superior properties. The volume fraction of nanofillers beyond which the sharp rise in the conductivity happens is called the percolation threshold. To make it cost efficient while retaining the performance, one approach is to use mixture of nanofillers. |
Wednesday, March 7, 2018 3:30PM - 3:42PM |
P46.00006: Measuring heat transport within polymer nanocomposites via fluorescence thermometry Gabriel Firestone, Jeffrey Meth, Laura Clarke, Jason Bochinski Measuring heat transport within complex polymeric systems with several different components is important for applications ranging from electronics to solar cells. Previously we reported a scheme whereby spot heating with a laser combined with measurement of the resultant temperature profile within a polymer thin film could be utilized to measure heat loss from film surfaces. An extension of this technique is presented to alternatively measure heat transport within a polymeric film laminated to a sensing layer. Such a scheme might be useful for testing materials intended for heat management applications. The sensing layer contains embedded metal nanoparticles, which will generate heat when irradiated with light resonant with their localized surface plasmon resonance, and molecular fluorophores that can be utilized to make a spatial map of the temperature versus position in the plane of the sensing layer. Because this radial temperature distribution depends on heat loss from the lateral surfaces, a simple fit of this profile provides information about heat transport in the attached film. We present experimental data and a theoretical analysis. |
Wednesday, March 7, 2018 3:42PM - 3:54PM |
P46.00007: Steady-state temperature gradients within polymer nanocomposites undergoing continuous-wave photothermal heating Laura Clarke, Gabriel Firestone, Somsubhra Maity, Jason Bochinski Metal nanoparticles act as nanoscale heaters via light-induced excitation of a localized surface plasmon resonance which converts the optical energy into local heat. Polymer films doped with a small concentration of nanoparticles can then be probed by applying internal heat at meso-length scales. Steady-state temperatures within a polymer matrix embedded with gold nanorods undergoing photothermal heating using continuous-wave excitation are measured in the immediate spatial vicinity of the nanoparticle (i.e., local temperature) from observing the rate of physical rotation of the asymmetric nanoparticles within the locally created polymer melt. Average temperatures across the entire sample (i.e., global temperature) are simultaneously observed using a fluorescence method from randomly dispersed molecular emitters. Comparing these independent measurements clearly demonstrates the presence of large steady-state spatial temperature gradients. Photothermal heating in this manner has potential utility in creating unique thermal processing conditions for outcomes such as driving chemical reactions, inducing crystallinity changes, or enhancing degradation processes in a manner unachievable by conventional heating methods. |
Wednesday, March 7, 2018 3:54PM - 4:06PM |
P46.00008: Effect of C60 on the Morphology of Strongly Segregated ABC Miktoarm Terpolymers Matthias Arras, Hyeyoung Kim, Monojoy Goswami, Jyoti Mahalik, Weiyu Wang, Sergey Chernyy, Kunlun Hong, Bobby Sumpter, Thomas Russell, Gregory Smith ABC miktoarm terpolymers place severe constraints on the configuration of immiscible polymer chains due to the joining at one junction point. We investigated the effect of C60 nanoparticles on a series of poly(styrene), poly(isoprene), poly(2-vinylpyridine) (PS-PI-P2VP) miktoarms by small angle scattering. To this end, we synthesized PS-PI-P2VP with symmetric PS and PI blocks and varied the degree of polymerization for P2VP. We denote the ratio between the volume fraction of P2VP and PS (or PI) as α. C60 addition leads to a reduction of the repeat period due, more than likely, to chain relaxation, in PS-PI-P2VP of the hierarchical lamellar morphology (HLM) which forms for α>∼2. In contrast, in a sample with a tiling morphology (TM) at short P2VP chains (α<1), we find the opposite behavior and the repeat period expands dramatically. We explain these distinct differences with the stability of the HLM (observed for ∼2>α>∼4) which thus appears rather insensitive to topological changes. In contrast, at all-symmetric conditions α=1 and below α<1 many TMs in close proximity are reported which means the morphology is susceptible to changes. |
Wednesday, March 7, 2018 4:06PM - 4:18PM |
P46.00009: Improving Superhydrophobicity of PDMS by Embedding Fluorinated POSS Cages Buddhika Gayani, Nilwala Kottegoda, Manjula Weerasekara, Dilru Ratnaweera Designing superhydrophobic surfaces is one of the value addition processes for biomedical polydimethylsiloxanes (PDMS) devices, which can be obtained by increasing nanoscale surface roughness and introducing low surface energy molecules. Current work explores simple fabrication methods that enhance the hydrophobicity of PDMS while retaining the durability. Two species of polyhedral oligomeric silsesquioxanes with short fluorocarbon tethers (FPOSS) were incorporated into PDMS using four methods. These methods were non-solvent blending, solvent blending, spraying FPOSS/PDMS solution onto partially cured PDMS and spraying only FPOSS solution onto partially cured PDMS surfaces. Among them, spraying FPOSS onto partially cured PDMS served the highest hydrophobicity with water contact angle of 167°. Trifluoropropylisobutyl POSS always consisted of higher hydrophobicity rather than trifluoropropyl POSS. Hence, the compatibility of functional groups attached to FPOSS has played a major role other than increasing the fluorine composition. Amorphous nature of the PDMS was improved upon incorporating FPOSS and it was method dependent. Hydrophobicity and durability of the spray coated PDMS-FPOSS blends confirms the possibility of using those in biomedical devises. |
Wednesday, March 7, 2018 4:18PM - 4:30PM |
P46.00010: Observing heterogeneous polymer degradation due to photothermal heating via electron imaging and optical measurements Honglu Huang, Daniela Fontecha, Gabriel Firestone, Russell Gorga, Jason Bochinski, Laura Clarke We observe the effects of thermally-driven chemical reactions (e.g., polymer degradation) occurring in small volumes within a solid material, where diffusion of reactants and products is limited. Such experiments are achieved by photothermally heating metal nanoparticles incorporated within a matrix. Exposure to light matching the nanoparticle’s localized surface plasmon resonance results in significant heat generation at the particle and an overall inhomogeneous steady state temperature distribution. Within the solid material, regions far from any particle are cooler relative to a particle's immediate vicinity, which can experience temperatures of 100-200 °C at moderate light intensities. Such heterogeneous heating complicates analysis of the degradation as highly degraded regions are intermingled with intact polymer. Electron microscopy imaging of photothermally-treated samples provides a physical map of the strongly-heated areas which contain deteriorated polymer having a different contrast than undamaged material. In addition, homogenous incorporation of fluorescent molecules provides an in-situ internal thermometer, a means to detect polymer degradation due to changes in local stiffness, and the ability to spatially map both quantities. |
Wednesday, March 7, 2018 4:30PM - 4:42PM |
P46.00011: Pressure-dependent structure and mechanics of grafted gold nanoparticle superlattices J. Matthew Lane, Ishan Srivastava, Brandon Peters, Hongyou Fan, Gary Grest, K. Michael Salerno Recent experiments have demonstrated synthesis of various gold nanostructures—e.g. nanowires, nanorods and nanosheets—through compression of self-assembled superlattices of polymer-grafted gold nanoparticles. The magnitude and direction of compression required to synthesize a certain nanostructure critically depend upon the mechanical properties of the superlattice. Using MD simulations, we examine the microstructure and mechanics of self-assembled fcc superlattices of alkanethiol-coated gold nanoparticles. We characterize the elastic moduli of these superlattices at various hydrostratic pressures up to 10GPa, as a function of ligand length, ligand grafting density, size of the gold core, and gold-sulfur bond strength. We establish that ligand microstructure and ligand migration on the gold surface crucially governs the emergent mechanical properties of the superlattice. These observations provide key inputs for optimizing compression driven synthesis of gold nanostructures. |
Wednesday, March 7, 2018 4:42PM - 4:54PM |
P46.00012: A pseudo-thermodynamic description of dispersion for nanocomposites. Yan Jin, Greg Beaucage, Karsten Vogtt, Hanqiu Jiang, Vikram Kuppa, Kabir Rishi, Vishak Narayanan, Alex McGlasson, Jan Ilavsky Dispersion in polymer nanocomposites is determined by the kinetics of mixing and chemical affinity. Compounds like reinforcing filler/elastomer blends display some similarity to colloidal solutions in that the filler particles are close to randomly dispersed through processing. It is attractive to apply a pseudo-thermodynamic approach taking advantage of this analogy between the kinetics of mixing for polymer nanocomposites and thermally driven dispersion for colloids. Measured values of the pseudo-second order virial coefficient can be used to specify repulsive interaction potentials for coarse grain DPD simulations of filler/elastomer systems. In addition, new methods to quantify the filler percolation threshold and filler mesh size as a function of filler concentration are obtained. |
Wednesday, March 7, 2018 4:54PM - 5:06PM |
P46.00013: Enhanced Mechanical Property of Polymer Nanocomposites Using Dopamine-Modified Polymers at Nanoparticle Surfaces Na Kyung Kwon, Hyunhong Kim, Imkyung Han, Tae Joo Shin, Jongnam Park, So Youn Kim The mechanical reinforcement of polymer nanocomposites (PNCs) relies on the microscopic details, typically the particle dispersion in polymer matrix. While chemical grafting method is common, and usually considered to effectively control particle dispersion, this method requires intricate grafting chemistry and experimentally expensive. Here, we report the improved mechanical property of unentangled poly(ethylene glycol) (PEG) can be obtained by employing the dopamine-derived PEG (DOPA-PEG) brush polymers. The DOPA-PEG is easily adsorbed onto silica nanoparticles via strong H-bonding, increasing the effective size of particles in PEG matrix. The microstructure and rheological properties of particles are strongly influenced by the surface coverage density of DOPA-PEG. One intriguing result is that the shear modulus of PNC with DOPA-PEG can be enhanced by 105 times, compared to the PNCs without DOPA-PEGs. The detailed microstructure and rheology are studied by small angle X-ray scattering (SAXS) and oscillatory rheological experiments. |
Wednesday, March 7, 2018 5:06PM - 5:18PM |
P46.00014: Abstract Withdrawn |
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