Influence of Differences in Molecular structure on Behavior of and β Relaxation Processes in Diisooctyl Maleate.

Dielectric relaxation measurements have been performed to study effect of the molecular structure on the primary and secondary relaxations in two materials with very similar structure: diisooctyl phthalate (DIOP) and diisooctyl maleate (DIOM). The dielectric spectra were measured over ten decades of frequency and a broad range of temperature. The results show that the temperature dependence of the α-relaxation times cannot be described by a single Vogel-Fulcher-Tammann equation and the temperature dependence of the β-relaxation times in the glassy state obey the Arrhenius law with different activation energies, i.e., EA/k = 4231 K and EA/k = 2917 K for DIOP and DIOM, respectively. Moreover, third relaxation process visible as an excess wing of the high frequency part of the α loss peak was identified in dielectric spectra of DIOM. [ABSTRACT FROM AUTHOR]