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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Segmental Diffusion in Attractive Polymer Nanocomposites: A Quasi-Elastic Neutron Scattering Study
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Polymer Diffusion Is Fastest at Intermediate Levels of Cylindrical Confinement
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Polymer Conformations and Dynamics under Confinement with Two Length Scales
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Structurally Tailored and Engineered Macromolecular (STEM) Gels as Soft Elastomers and Hard/Soft Interfaces
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Kinetics and Energetics of Solute Segregation in Granular Block Copolymer Microstructures
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Impact of Hydrogen Bonding Interactions on Graft–Matrix Wetting and Structure in Polymer Nanocomposites
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Engineering Scale Simulation of Nonequilibrium Network Phases for Battery Electrolytes
According to the article, Diblock copolymers play an important role in the fabrication of battery materials and fuel cells. For these applications, one block provides mechanical stability, whereas the other is conducting. The application characteristics of the material critically depend on the morphology of the multicomponent material, and three-dimensional, percolating domains of the conducting domains are preferred. In this work, we investigate the nonequilibrium morphology of diblock copolymers after a quench from the disordered phase. After the spinodal self-assembly, we observe three-dimensionally percolating network structures for volume fractions, f ≥ 8/32, of the conducting component even if the equilibrium phases exhibit different percolation properties. We quantify the conductivity and tortuosity of these structures via a simple random-walk model and observe that the conductivity of the nonequilibrium structures is significantly smaller than that of the equilibrium phases. We also find large but finite-sized, fractal-like structures inside the morphology, which influence the transport properties. To explore the morphology on different scales and mitigate finite-size effects, we employ very large simulations with billions of particles. Our work demonstrates that for the prediction of bulk transport properties in these nonequilibrium morphologies it is necessary to study such large system sizes.
Poly(olefin)-Based Anion Exchange Membranes Prepared Using Ziegler–Natta Polymerization
Bromoalkyl-functionalized poly(olefin)s were synthesized by copolymerization of 4-(4-methylphenyl)-1-butene with 11-bromo-1-undecene using Ziegler–Natta polymerization. The resulting bromoalkyl-functionalized poly(olefin)s were converted to quaternary ammonium-containing anion-conductive copolymers by reacting the pendant bromoalkyl group with trimethylamine or a custom-synthesized tertiary amine containing pendant quaternary ammonium moieties. Poly(olefin)-based AEMs with three cations per side chain showed considerably higher hydroxide conductivities, up to 201 mS/cm at 80 °C in liquid water, compared to that of samples with only one cation per bromoalkyl site (68 mS/cm, 80 °C, liquid water), likely due to phase separation in the triple-cation structure. More importantly, triple-cation side-chain poly(olefin) AEMs exhibited higher hydroxide conductivity under relative humidity conditions (50%–100%) than typical AEMs based on benzyltrimethylammonium cations. Here, the triple-cation the triple-cation side-chain poly(olefin)-based AEM exhibited an ionic conductivity as high as 115 mS/cm under 95% RH at 80 °C and 11 mS/cm under 50% RH at 80 °C. In addition to high ionic conductivity, the triple-cation side-chain poly(olefin) AEMs exhibited good chemical and dimensional stability. High retention of ionic conductivity (>85%) was observed for the samples in 1 M NaOH at 80 °C over 1000 h. Based on these high-performance poly(olefin) AEMs, a fuel cell with a peak power density of 0.94 W cm –2 (1.28 W cm –2 after iR correction) was achieved under H 2 /O 2 at 70 °C. The results of this study suggest a new, low-cost, and scalable route for preparation of poly(olefin)-based AEMs for anion exchange membrane applications.
Electrokinetics in Viscoelastic Liquid Electrolytes above the Diffusion Limit
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Molecular Parameters Governing the Elastic Properties of Brush Particle Films
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Dueling Backbones: Comparing Peptoid and Peptide Analogues of a Mussel Adhesive Protein
Ensembles of amino acid side chains often dominate the interfacial interactions of intrinsically disordered proteins; however, backbone contributions are far from negligible. Using a combination of nanoscale force measurements and molecular dynamics simulations, we demonstrated with analogous mussel-mimetic adhesive peptides and peptoids both 34 residues long that highly divergent adhesive/cohesive outcomes can be achieved on mica surfaces by altering backbone chemistry only. The Phe, Tyr, and Dopa containing peptoid variants used in this study deposited as dehydrated and incompressible films that facilitated analysis of peptoid side chain contributions to adhesion and cohesion. For example, whereas Phe and Dopa peptoids exhibited similar cohesion, Dopa peptoids were ~3 times more adhesive than Phe peptoids on mica. Compared with the peptides, Phe peptoid achieved only ~20% of Phe containing peptide adhesion, but the Dopa peptoids were >2-fold more adhesive than the Dopa peptides. Cation-π interactions accounted for some but not all of the cohesive interactions. Finally, our results were corroborated by molecular dynamics simulations and highlight the importance of backbone chemistry and the potential of peptoids or peptoid/peptide hybrids as wet adhesives and primers.