INVESTIGATION OF H2SO4-DOPED, RING-DEUTERATED POLY(PARA-PHENYLENE VINYLENE) USING SOLID-STATE H-2 QUADRUPOLE ECHO NMR-SPECTROSCOPY

Ring-deuterated poly(p-phenylene vinylene) has been doped with concentrated sulphuric acid and examined with H-2 quadrupole echo nuclear magnetic resonance spectroscopy. Doping is observed to change the relative population of fast versus slow flipping p-phenylene rings. This relationship has been investigated over a range of temperatures. Modelling this system as a two-site chemical exchange shows that the change in the relative populations of fast versus slow 'flippers' corresponds to an increase in the activation energy for the 180-degrees ring flip. The width of the distribution of flip rates is also observed to increase upon doping. At elevated temperatures the samples studied undergo a significant loss of mass which corresponds to a loss of dopant. The chemistry of this process is examined.