Electron spin resonance study of rotational and translational diffusion in Polystyrene solutions

Includes bibliographical references (page 47)The hydrodynamic properties of solutions of polystyrene\ud in toluene were studied with the spin probe Di-tert-butylnitroxide: DTBN The effect on the translational diffusion\ud of DTBN due to the presence of macromolecules was studied\ud using spin exchange. The rotation of the spin probe was\ud investigated from the linewidth variation of the EPR spectrum\ud at low spin probe concentration. Increasing concentrations\ud of the polymer were used leading to a nearly\ud twenty-five fold increase in the viscosity. Three different\ud molecular weights of polystyrene were used : 2000, 300,000\ud and 1,800,000 . Rotational correlation times, translational\ud diffusion coefficients, and hyperfine coupling constants\ud derived from the data show that the hydrodynamic environment\ud is remarkably unaffected by the presence of the polymer and\ud the increased viscosity. A simple model that envisions very\ud little interaction between the DTBN and polystyrene molecules\ud explains the results well