SELF-DIFFUSION IN COMPRESSED DIMETHYLETHER - THE INFLUENCE OF DIPOLE-DIPOLE INTERACTION AND HYDROGEN-BONDING UPON TRANSLATIONAL DIFFUSIVITYIN SIMPLE FLUIDS

Self-diffusion coefficients of dimethylether have been measured as a f unction of temperature (185-458 k) and pressure (up to 200 MPa) by pul se-gradient field spin-echo NMR. Calculated activation volumes (Delta V-not equal ) fall from 15 (10(-6) m(3)/mole) at the highest temperatu re to 7 (10(-6) m(3)/mole) at the lowest. This trend is in keeping wit h values for other non-associating liquids. Comparision with self diff usion data for propane and ethanol reveals that the translational diff usivity in dimethylether is influenced by the substance's modest dipol e moment (1.3 Debye). The effect is small but measurable and becomes m ore pronounced at lower temperatures.