Ultrasonic shear relaxation data are reported for the associated liquid pentanediolminus;1,5 at frequencies between 13 and 470 Mc/sec. Reduction of the data indicates a relatively narrow distribution of relaxation times. Viscosity data are also reported on this liquid which show a slight but definite deviation from Arrhenius behavior (lneegr;sprop;1/T). The shear data are compared to that for two other diols: 2hyphen;methyl pentanediolminus;2,4 and butanediolminus;1,3. In this comparison it is shown qualitatively that the width of the distribution of shear relaxation times increases as the temperature dependence of the average relaxation time deviates from the Arrhenius form. It is argued that the origin of both the nonhyphen;Arrhenius character of the average shear relaxation time and the distribution of these times lie in cooperative molecular motion.
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