Quinaldine: Accessing two crystalline polymorphs via the supercooled liquid

Robert Kahlau, Tanja Gnutzmann, Franziska Emmerling, Klaus Rademann, Ernst A. Rössler
2012 Journal of Chemical Physics  
Quinaldine (2-methyl quinoline) is a liquid at room temperature, which can be supercooled to reach finally the glassy state. By heating the glass above the glass transition temperature T g = 180 K the sample performs two subsequent transitions into, likewise, dielectrically active phases. Thus, the reorientational relaxations of these phases as well as the kinetics of the phase transitions can be tracked in a highly resolved way by dielectric spectroscopy. X-ray diffraction analysis clearly
more » ... s two structurally different crystalline phases in addition to the supercooled liquid. Calorimetric measurements support the notion of first order phase transitions, occurring irreversibly in the supercooled regime, and suggest that the intermediate crystalline phase is metastable, too. Analyzing the quite distinct dielectric relaxation strengths, we discuss the possible nature of the two crystalline phases. Additionally, a very similar behavior to quinaldine is observed for 3-methyl quinoline, indicating a broad field of polymorphism among the quinoline derivatives.
doi:10.1063/1.4738583 pmid:22894362 fatcat:re5k2w3lardndhwlwzydnf32lu