The dielectric permittivity and the dielectric loss factor of 5‐methyl‐3, 4‐methyl‐3 and 3‐methyl‐3‐heptanol, n‐ and iso‐butanol, 1,2‐propanediol, dimethyl and diethyl phthallate, and 3‐methylpentane have been measured from 50 to 105 Hz and from −196 to about 20°C above their respective glass transition temperatures. The glass transition temperature Tg of these substances, several more isomeric octanols, and 1‐phenyl‐1‐propanol have been measured by differential thermal analysis. All substances except for 3‐methylpentane and iso‐butanol show either a well‐defined secondary relaxation peak in tanδ, or a clear indication of the presence of a secondary relaxation below their . Arrhenius plots for the α‐relaxation process of the isomeric octanols are linear with an activation energy of 16–18 kcal/mole, while for other substances they are nonlinear with the activation energy changing from 30 to 70 kcal/mole. The Arrhenius plots for the secondary relaxations are linear and have an activation energy of 4–8 kcal/mole. It is pointed out that the presence of a spectrum of relaxation times in liquids near Tg is not necessarily concomitant with non‐Arrhenius behavior. It is concluded that the presence of secondary relaxations should be considered as a characteristic property of the liquid in or near the glassy state, and do not require specific intramolecular mechanisms for their existance.
Viscous Liquids and the Glass Transition. III. Secondary Relaxations in Aliphatic Alcohols and Other Nonrigid Molecules
Gyan P. Johari, Martin Goldstein; Viscous Liquids and the Glass Transition. III. Secondary Relaxations in Aliphatic Alcohols and Other Nonrigid Molecules. J. Chem. Phys. 1 November 1971; 55 (9): 4245–4252. https://doi.org/10.1063/1.1676742
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