DIRECT ELECTRON-TO-CARBON POLARIZATION TRANSFER IN HOMOGENEOUSLY DOPED POLYCARBONATES

A direct electron-to-carbon DNP solid-effect polarization transfer is observed for the aromatic and carbonyl carbons of polycarbonate homogeneously doped with BDPA (see previous papers for notation). The direct electron-to-carbon polarization transfer operates over a range of 30-60 angstrom. Carbons that are closest to the free radicals are polarized first and have the longest spin-lattice relaxation times. Fourier transforms of time-domain magnetization, synchronously detected under combined chemical-shift and C-H dipolar interactions, show an asymmetrical sideband pattern in the dipolar frequency dimension. Simulations that qualitatively agree with the observed asymmetrical sideband patterns are obtained by assuming that molecular motion in the vicinity of the bulky free radical is reduced.