Broadband Dielectric Measurement Techniques For Relaxation Dynamics Of Glass-forming Monohydroxy Alcohols

The relaxation behavior of the supercooled liquid have been studied extensively togain insight into the nature of glass transition. The exponential process of monohydroxyalcohols is only seen by dielectric spectroscopy, which could not be detected by othermethods,such as mechanical and light scattering measurements. In this work, weexperimentally study the Debye relaxation of monohydroxy alcohols by dielectricrelaxation technique and the physical origin of Debye relaxation.Glass-forming monohydroxy alcohols exhibit not only a non-Debye relaxation butalso a slower, single-exponential Debye-type relaxation process which already freezes inthe liquid phase. It is found that the Debye process don’t have the character of structurerelaxation, we experimentally analyze the true structure relaxation though comparing withcalorimetric characteristic parameter-glass transition temperatures Tg. The study focuseson two binary systems of primary alcohols2-ethyl-1-hexanol and2-ethyl-1-butanol, wefind that the logarithmic relaxation time logτ of the Debye peak follows an ideal mixinglaw (linear change with mole fraction), even in the case of mixing structurally dissimilarcomponents.However, the mixtures of2-ethyl-1-butanol and4-methyl-2-pentanol, binaryisomeric mixtures of primary and secondary alcohols, we find the logarithmic relaxationtime logτ of the Debye peak don’t follow the ideal mixing law and two mixed Debyeliquids is capable of giving rise to an enhancement in dielectric strength associated withthe Debye relaxation. Molecular structure could have a significant influence on the Debyerelaxation strength, including-OH position, chain length, and branched groups positionand space volume, leading to the disappearance of the Debye feature. Compared to theprimary alcohols, secondary alcohols and tertiary alcohols could make the Debye peakweaker even disappeared, and so could longer chain and larger branched groups.Long-chain monohydroxy alchols have low dieletric strength and are sensitive totemperature change. As the number of carbon atoms increases, the behavior of thedominating process transforms from exponential to non-exponential and activation plothas non-Arrehenius characteristic. The application of pressure to2-ethyl-1-hexanol hassimilar experimental phenomenon. We have studied two binary system of 1,2-propanediamine and2-ethyl-1-hexanol. When the mole fraction of2-ethyl-1-hexanoldecreases to70%, the Debye relaxation disappears completely. We have discussed thereason why amine materials have strong destruction on Debye relaxation. We haveanalysed the changes of the strength of Debye peaks of various binary glass-forming alongwith-OH concentration. According to experimental phenomenons, we discuss the newfeatures and the physical origin of the Debye relaxation.