Experimental study of the high frequency relaxation process in monohydroxy alcohols

Murthy, S. S. N.; Tyagi, Madhusudan
August 2002
Journal of Chemical Physics;8/22/2002, Vol. 117 Issue 8, p3837
Academic Journal
We have critically examined the possibility of the existence of yet another process (often referred to as process II in the literature) of much smaller magnitude on the high frequency side in the case of 2-ethyl-1-hexanol and 4-methyl-3-heptanol using the dielectric relaxation technique. We have also studied the mixtures of 2-ethyl-1-hexanol with nonpolar methylcyclohexane and a mixture of 1-bromobutane in 4-methyl-3-heptanol for this purpose. In addition, the differential scanning calorimetry (DSC) has been used to study the structural relaxation in the vicinity of the glass transition temperature using the Tool-Narayanaswami-Moynihan procedure as discussed by Sartor et al. [J. Phys. Chem. 100, 6801 (1996)]. Our results show the presence of a clear process II on the higher frequency side whose freezing-out corresponds to the glass transition event at T[sub g] in the DSC studies. It is suggested that process II is associated with free alcohol molecules and is connected to the structural relaxation in alcohols. The dielectric data have been analyzed to understand the thermodynamics of hydrogen bonding using the model of Dannhauser [J. Chem. Phys. 48, 1911 (1968)]. An attempt has been made to correlate the ratio of relaxation rates of processes I and II and the observed deviation from Debye behavior in the case of alcohols.


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