Abstract
Dielectric behavior and glass formation in supercooled liquid guaifenesin (GFN) and its binary liquids with acetaminophen (ACT), and of ACT with mephenesin (MP), are reported using dielectric spectroscopy (10−3 Hz–2 MHz) and differential scanning calorimetry down to liquid nitrogen temperature. Solid–liquid phase equilibria of ACT + GFN and ACT + MP exhibit a simple eutectic of complete miscibility in the liquid state with eutectic points at 344.6 (±1) K and 337.5 (±1.4) K, respectively, and separate into two crystalline components in the solid state. The glass transition temperature (Tg) measured for quenched binary liquids obeys a mixture rule. The primary relaxation process (α-process), can be well described by the Havriliak–Negami equation. A secondary relaxation process (β-process), found below Tg, is Arrhenius in its temperature dependence, but may not be of inter-molecular or Johari–Goldstein (JG) type in nature. The “fragility” of the samples is discussed in the context of a coupling model. The supercooled liquid samples and binary liquids studied here are found to be “very fragile” in nature.
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