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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Revisit of polystyrene-modified fullerene core stars: A computational study

Density functional theory (DFT) calculations have been used to clarify the number of poly(styryl) lithium anions that are grafted onto C 60 fullerene. The computational results suggest that 6-arm-grafted C 60 fullerene is the most thermodynamically favorable, and the grafted C 60 fullerene with arms more than 6 is only achievable under certain circumstances. This observation is consistent with the previous experiments [Macromolecules 2013; 46:7451–57.]. Both electronic effect and steric effect have been thoroughly examined and they are found to play different roles in the arm-grafted C 60 fullerene. Our study will pave a way for the future architecture of polymers on C 60 fullerene and the like.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

The role of nanoparticle rigidity on the diffusion of linear polystyrene in a polymer nanocomposite

The impact of the inclusion of a nanoparticle in a polymer matrix on the dynamics of the polymer chains is an area of recent interest. In this article, we describe the role of nanoparticle rigidity or softness on the impact of the presence of that nanoparticle on the diffusive behavior of linear polymer chains. The neutron reflectivity results clearly show that the inclusion of 10 nm soft nanoparticles in a polymer matrix (R g ~ 20 nm) increases the diffusion coefficient of the linear polymer chain. Surprisingly, thermal analysis shows that these nanocomposites exhibit an increase in their glass transition temperature, which is incommensurate with an increase in free volume. Therefore, it appears that this effect is more complex than a simple plasticizing effect. Results from small-angle neutron scattering of the nanoparticles in solution show a structure that consists of a gel like core with a corona of free chain ends and loops. Furthermore, the increase in linear polymer diffusion may be related to an increase in constraint release mechanisms in the reptation of the polymer chain, in a similar manner to that which has been reported for the diffusion of linear polymer chains in the presence of star polymers.

36 MATERIALS SCIENCE↗