Synthesis and Wide-Line NMR Studies of Alpha-Deuterated Polyacrylates and Polyacrylonitrile
Polymers and High Performance Materials
By use of a simple, direct hydrogen-exchange reaction, deuterated vinyl compounds have been synthesized. Acrylate esters, acrylonitrile, and methyl vinyl ketone were found to undergo rapid exchange at room temperature to give easily isolated, pure, and readily polymerizable alpha-deuterated derivatives. Selected monomers were polymerized and the obtained polymers examined by solid-state deuterium nuclear magnetic resonance spectroscopy. The NMR data show that the acrylate polymers are rigid below T(g) and move quickly and randomly at temperatures ca. 20-40-degrees-C above T(g). The same type of motion is seen for cross-linked acrylates labeled either on the main chain or at the cross-link, but a different temperatures. That is, H-2-labeled cross-link sites become mobile at ca. 10-degrees-C lower than H-2-labeled segments between cross-links. In contrast, polyacrylonitrile displays unusual deuterium line shapes due to a well-defined motion above its glass transition. T2 values determined at various temperatures show a minimum at ca. 30-degrees-C above the T(g) for all polyacrylates while their T1 minima were at approximately the same values as the DSC T(g)'s. For polyacrylonitrile, the wide-line spectra did not show large-scale motional averaging even up to 435 K, 60-65-degrees-C above the DSC T(g) value, and T2 and T1 plots did not show behavior similar to the acrylates.
Mathias, L. J.,
Colletti, R. F.
(1991). Synthesis and Wide-Line NMR Studies of Alpha-Deuterated Polyacrylates and Polyacrylonitrile. Macromolecules, 24(20), 5515-5521.
Available at: http://aquila.usm.edu/fac_pubs/7088