NMR and Raman spectroscopic characterization of single walled carbon nanotube composites of polybutadiene.

Significant shifts of the frequency of the Raman spectra of the tangential mode of single walled carbon nanotubes (SWNTs) and fluorinated tubes (FSWNTs) in composites of polybutadiene (PB) were observed relative to the pristine SWNTs indicative of the interaction between the polymer and the SWNTs. Proton NMR line width measurements demonstrate partial suppression of polymer segmental motion for both types of nanotube composites and spin-lattice relaxation results indicate that short time-scale localized motions are also affected by SWNT inclusion, more so for FSWNTs. Hardness measurements as a function of wt% SWNTs and FSWNTs in the polymer show larger enhancements of hardness in the composite with the fluorinated tubes.

Factors Influencing 1,4-Asymmetric Induction during Indium-Promoted Coupling of Oxygen-Substituted Allylic Bromides to Aldehydes in Aqueous Solution.

The preparation and indium-promoted aldehyde addition reactions of a series of 3-substituted 3-oxy-1-bromo-2-methylidenepropanes under aqueous conditions are described. The (tert-butyldimethylsilyl)oxy derivatives 4a-d are the most diastereoselective of this group of reagents, giving rise to levels of syn-1,4-asymmetric induction in the range of 87-99%. Interestingly, syn stereoselectivity is eroded and reactions proceed more rapidly when the steric bulk of the oxygen substituent is reduced as in the hydroxy and methoxy derivatives.