Primary and secondary relaxations in aliphatic alcohols: Complex dielectric permittivity spectra of 5-methyl 2-hexanol

Abstract

The real and imaginary parts of the complex dielectric permittivity of 5-methyl 2-hexanol have been measured in the frequency range 10 Hz to 100 kHz and temperature range 77 K to 200 K. The results show the existence of two Arrhenius relaxation processes, assigned as α and β. It is found that these processes co-exist above the glass transition temperature, T g. However the β process persists in the glass structure with continually reduced dielectric relaxation strength and broader distribution of dielectric relaxation times with a reduction in temperature. This continues on until some 60 K below T g. Our investigation of these processes in this material and other materials already published support the glass transition theory of Johari and Goldstein that β process is generic to the glass phase of supercooled liquids. A plausible explanation of the Arrhenius nature of the α relaxation process for alcohols is also given.