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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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At least 1,351 records · Page 75
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

Hierarchically structured bicontinuous polymeric microemulsions

We recently described the synthesis and phase behavior of a new type of CECEC-P multiblock copolymer composed of glassy poly(cyclohexylethylene) (C), semicrystalline poly(ethylene) (E), and elastomeric poly(ethylene-alt-propylene) (P) with symmetric (equal volume) CECEC and P sequences (G. Fleury and F. S. Bates, Macromolecules, 2009, 42, 3598-3610). Here we report the formation and characterization of a multicontinuous structure based on the blending of CEC triblock copolymer and P homopolymer with such a hexablock copolymer along the 50:50 (CEC/P) isopleth. These materials produce a sequence of phases that are correlated with the volume fraction of CECEC-P as evidenced by SAXS and TEM measurements. A percolating bicontinuous mesostructure was identified at volume fractions of hexablock copolymer, f{sub CECEC-P} = 0.10 and 0.125, within the composition range known to result in a bicontinuous morphology in A-B/A/B systems. A solid product was formed by cooling the initially homogeneous ternary mixture from above the melting temperature of the E blocks to room temperature. Crystallization of E leads to microphase separation of C and E and simultaneous ejection of P from CEC (and CECEC) at a larger length scale. The mechanical properties of these materials are inferior to what is anticipated based on pure CEC triblock copolymer, attributable to the low molecular weight and irregular structure of the C/E region sequences. Nevertheless, this study establishes a procedure for producing bicontinuous yet structurally asymmetric materials based on the microemulsion process and extends the concept of a microemulsion to multiblock copolymers.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Simultaneous cross-linking and p-doping of a polymeric semiconductor film by immersion into a phosphomolybdic acid solution for use in organic solar cells

Poly[ N -9'-heptadecanyl-2,7-carbazole- alt -5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT) is shown to be simultaneously cross-linked and p-doped when immersed into a phosphomolybdic acid solution, yielding conductive films with low solubility that can withstand the solution processing of subsequent photoactive layers. Furthermore, such a modified PCDTBT film serves to improve hole collection and limit carrier recombination in organic solar cells.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Rapid room temperature solubilization and depolymerization of polymeric lignin at high loadings

The relatively poor solubility of lignin in most pretreatment solvents remains one of the biggest challegnes in lignin valorization to improve overall biorefinery economics. In this work, rapid room temperature solubilization of lignin at high solid loadings (>30 wt%) can be easily achieved in a single step using ethylene glycol (EG). The solubilized lignin can be rapidly and quantitively recovered with the addtion of ethanol. The computational and nuclear magnetic resonance (NMR) spectroscopic studies confirm that strong hydrogen bond interactions between EG and the free hydroxyl groups present in lignin contribute to the lignin dissolution. In addition, hydrogen peroxide mediated depolymerization of dissolved lignin at low temperature (80 oC) was tested and the effect of EG molecules on depolymerization of ligin was also theoritically studied. The findings of this work provide mechanistic insights of hydrogen bond interactions in high lignin solubilization and valorization.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2018

Microporous polymeric composite membranes with advanced film properties: pore intercalation yields excellent CO 2 separation performance

Polymers of intrinsic microporosity (PIMs) are revolutionary gas separation materials because of their ultra-high permeability, but suffer from low gas pair selectivity (for example CO 2 /N 2 ) and poor durability due to brittleness. In this paper, we present a simple solution to these problems by blending PIM-1 with compatible polymer blend composed of PIM-1 and an ether side chain polyphosphazene (MEEP80), which possesses better mechanical flexibility and higher CO 2 /N 2 selectivity than the native PIM-1 while maintaining high CO 2 permeability. Under mixed gas test conditions, a blend of 25 wt% MEEP80 in PIM-1 has a CO 2 permeability of 2440 barrer and a CO 2 /N 2 selectivity of 39 under mixed gas testing conditions, putting it among the best known polymers for CO 2 /N 2 separation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Synthesis, characterization, and polymerization of capped paddlewheel porous cages

Although paddlewheel-based structures are common among permanently porous metal–organic materials, suitable strategies for the isolation of metal node-terminated, capped paddlewheel-based cage structures remain limited. We explored the use of chelating dicarboxylate ligand derivates (esp) for the isolation of trimesate-linked cages, Mo 12 (btc) 4 (esp) 6 , that are structural analogs of the small octahedral pore of HKUST-1. The porosity of these novel cages is appreciably higher than that of previously reported structures of this type. We also demonstrate that pillaring the isolated cage with DABCO generated an amorphous polymer that featured exceptional thermal stability and enhanced porosity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗