Order Parameter of the Liquid-Liquid Transition in a Molecular Liquid.
Liquid-liquid transitions (LLTs) between amorphous phases of a single (chemically unchanged) liquid were predicted to occur in most molecular liquids but have only been observed in triphenyl phosphite (TPP) and n-butanol, and even these examples have been dismissed as "aborted crystallization". One of the foremost reasons that LLTs remain so controversial is the lack of an obvious order parameter, that is, a physical parameter characterizing the phase transition. Here, using the technique of fluorescence lifetime imaging, we show for the first time that the LLT in TPP is characterized by a change in polarity linked to changes in molecular ordering associated with crystal polymorphs. We conclude that the LLT in TPP is a phase transition associated with frustrated molecular clusters, explaining the paucity of examples of LLTs seen in nature.
School of Chemistry, WestCHEM, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
Joanna
J
Mosses
School of Chemistry, WestCHEM, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
Christopher D
CD
Syme
School of Chemistry, WestCHEM, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
Klaas
K
Wynne
coumarin 153; fluorescence lifetime imaging; liquid−liquid transition; polymorphs; triphenyl phosphite