BACKGROUND: While carbon nanotubes are highly interesting materials for a variety of applications, their inherent insolubility limits widespread applications and solution-phase processing. It is known that chemical functionalization can overcome this insolubility problem, and covalent grafting of polymers to the nanotube surface has been shown to be effective. In this study, the effect of polymer molecular weight on the solubility of polymer-nanotube conjugates was investigated.
RESULTS:A series of nitroxide-capped polystyrene polymers ranging in molecular weight from 2900 to 105 000 g mol −1 were grafted to single-walled carbon nanotubes (SWNTs). The resulting polystyrene-SWNT conjugates exhibited different degrees of solubility in tetrahydrofuran. Subsequent thermogravimetric and UV-visible spectroscopy analyses indicated that carbon nanotube solubility reached a maximum when a polymer sample with a weight-average molecular weight of 10 000 g mol −1 was used. Higher and lower molecular weights resulted in reduced solubilities.
CONCLUSION: Polymer chains of intermediate length maximize SWNT solubility, while lengths that are too low or too high seem to diminish the ability of the polymer-SWNT conjugates to remain in solution.
. -The one-pot three-component reaction between carbonyl double-allylation reagent (I) and aldehydes (II) affords the cis-trisubstituted tetrahydrofurans (IV) in high enantio-and diastereoselectivity. A similar procedure applied to dicarbonyl substrate (V) under dilute conditions yields an oxabicyclic compound (VI) embedding an eight-membered medium ring. -(SIVASUBRAMANIAM, U.; HALL*, D. G.;
The one‐pot three‐component reaction between carbonyl double‐allylation reagent (I) and aldehydes (II) affords the cis‐trisubstituted tetrahydrofurans (IV) in high enantio‐ and diastereoselectivity.
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