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Conformation of Single Pentablock Ionomer Chains in Dilute Solutions

Sandia journal manuscript; Not yet accepted for publication

Aryal, Dipak; Perahia, Dvora; Grest, Gary S.

The conformation of single chain pentablock ionomers (A-B-C-B-A) containing randomly sulfonated polystyrene in the center block, tethered to poly-ethylene-r-propylene end-capped by poly-t-butyl styrene is studied in dilute solutions by molecular dynamics simulations. Multi-block copolymers offer a means to tailor several properties into one molecule, taking advantage of their rich phase diagram together with unique properties of specific blocks. For this pentablock the ionic block facilitates transport while the A and B components are incorporated for mechanical stability. The present study investigates the confirmation of a single chain of pentablock ionomer of molecular weight Mw ~ 50,000 g/mol and sulfonated polystyrene of the same molecular weight as that of the center block for six sulfonation fractions f from f=0.0-0.55. For the sulfonated systems Na+ counterions are included. Results for the equilibrium conformation of the chains and the three blocks in water and 1:1 mixture of cyclohexane and n-heptane are compared to simulations in implicit poor solvents with dielectric constants ε =1.0 and 77.73. In water, the pentablock is collapsed with sulfonated groups on the outer surface. As the sulfonation fraction f increases, the ionic, center block is increasingly segregated from the hydrophobic regions. In the 1:1 mixture of cyclohexane and heptane both the flexible and end blocks are swollen while the center ionic block is collasped for f>0, while for f=0 all blocks are swollen. In both implicit poor solvents the pentablock is collapsed into a nearly spherical shape for all f. The sodium counterions are dispersed widely throughout the simulation cell for both water and ε =77.73 whereas for ε =1.0 the counterions are largely condensed on the collapsed pentablock.

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TYPE Journal Article YEAR 2015
OSTI

Recent Progress and Future Potential of Magnetized Liner Inertial Fusion (MagLIF)

Sandia journal manuscript; Not yet accepted for publication

Slutz, Stephen A.; Gomez, Matthew R.; Sefkow, Adam B.; Sinars, Daniel; Hahn, Kelly; Hansen, Stephanie B.; Harding, Eric H.; Knapp, P.F.; Schmit, Paul; Jennings, Christopher A.; Awe, Thomas J.; Herrmann, M.C.; Hess, Mark H.; Johns, Owen; Lamppa, Derek C.; Martin, Matthew R.; Mcbride, Ryan; Geissel, Matthias; Rovang, Dean C.; Chandler, Gordon A.; Cooper, Gary; Cuneo, Michael E.; Harvey-Thompson, Adam J.; Peterson, K.J.; Porter, John L.; Robertson, G.K.; Rochau, G.A.; Ruiz, Carlos L.; Savage, Mark E.; Smith, Ian C.; Stygar, William A.; Vesey, Roger A.

The standard approaches to inertial confinement fusion (ICF) rely on implosion velocities greater than 300 km/s and spherical convergence to achieve the high fuel temperatures (T > 4 keV) and areal densities (ρr > 0.3 g/cm2) required for ignition1. Such high velocities are achieved by heating the outside surface of a spherical capsuleeither directly with a large number of laser beams (Direct Drive) or with x-rays generated within a hohlraum (Indirect Drive). A much more energetically efficient approach is to use the magnetic pressure generated by a pulsed power machine to directly drive an implosion. In this approach 5-10% of the stored energy can be converted to the implosion of a metal tube generally referred to as a “liner”. However, the implosion velocity is not very high 70-100 km/s and the convergence is cylindrical (rather than spherical) making it more difficult to achieve the high temperatures and areal densities needed for ignition.

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TYPE Journal Article YEAR 2015
OSTI

Better Incident Response with SCOT

Sandia journal manuscript; Not yet accepted for publication

Bruner, Todd

SCOT is an incident response management system and knowledge base designed for incident responders by incident responders. SCOT increases the effectiveness of the team without adding undue burdens. Focused on reducing the friction between analysts and their tools, SCOT enables analysts to document and share their research and response efforts in near real time. Automatically identifying indicators and correlating those indicators, SCOT helps analysts discover and respond to advanced threats.

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TYPE Journal Article YEAR 2015
OSTI

Confirming the Strength of Residential Roof Structures for Solar Installations

Sandia journal manuscript; Not yet accepted for publication

Dwyer, Stephen F.

Researchers at the U.S. Department of Energy’s Sandia National Laboratories conducted a first-ofits- kind study to help dispel misperceptions that many existing rooftops cannot carry the actual load created by rooftop solar photovoltaic (PV) installations. Test data on rooftop structure load capacity wasn’t previously available to the industry, and research to collect such data was made costly by the need to test each scaled structure to the point of failure. The Energy Department funded this study to provide scientific data to the industry that can decrease uncertainty, help eliminate misperceptions, and ultimately alleviate extraneous solar PV permitting costs.

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TYPE Journal Article YEAR 2015
OSTI
Results 48601–48700 of 99,299
Results 48601–48700 of 99,299