Dynamics of glass-forming liquids. XIII. Microwave heating in slow motion

Wei Huang, Ranko Richert

Research output: Contribution to journalArticle

68 Scopus citations

Abstract

Using time-resolved nonlinear dielectric relaxation measurements at fields as high as 450 kV/cm, the nonthermal effects of energy absorption are studied for simple and associating polar liquids in their supercooled state. The experiment is a low frequency analog of microwave heating and facilitates tracking the flow of energy in time, as it accumulates in slow degrees of freedom and transfers eventually to the vibrational heat bath of the liquid. Most findings agree with a phenomenological model of heterogeneous relaxation regarding structure and configurational temperature. The relevant thermal behavior of monohydroxy alcohols differs considerably from the cases of simple nonassociating liquids due to their distinct origins of the prominent dielectric absorption mode for the two classes of liquids. Nonthermal effects are observed as dynamics that are accelerated without increasing sample temperature, but for the present low frequencies the changes remain too small to explain the high efficiencies reported for microwave chemistry. Limitations as to how rapidly the faster relaxation time constants are able to adjust to temperature separate the modes of the dispersive α -relaxation into a "relaxation" and an "aging" regime, thereby explaining the incompatibility of heterogeneous dynamics with common physical aging observations.

Original languageEnglish (US)
Article number194509
JournalJournal of Chemical Physics
Volume130
Issue number19
DOIs
StatePublished - Jun 1 2009

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

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