Carbon-13 nuclear magnetic relaxation study of solvent effects on chain local dynamics of poly(N-vinylcarbazole) in dilute solution

Carbon-13 longitudinal relaxation times and NOE values were measured as a function of temperature at three magnetic fields for poly(N-vinylcarbazole) (PNVC) in five solvents, covering viscosities differing by a factor of 5. The relaxation data of the backbone carbons were interpreted in terms of chain local motions by using the bimodal time-correlation function of the Dejean-Laupretre-Monnerie (DLM) model. The molecular correlation times obtained from the DLM. model follow a linear relationship with solvent viscosity with unit slope, indicating that the hydrodynamic behavior of PNVC can be described by Kramers' theory. Several time-correlation functions describing internal motion failed to reproduce the experimental relaxation data of the protonated aromatic carbons of the carbazole side-group. It was concluded that the internal motion of the carbazole group is highly restricted due to strong steric effects from neighboring rings and the backbone chain. Finally, on the basis of our data some general conclusions were drawn regarding the influence of the backbone rearrangement of PNVC on its photophysical behavior.