AUTHOR=Drozd-Rzoska Aleksandra 

TITLE=Pressure-Related Universal Previtreous Behavior of the Structural Relaxation Time and Apparent Fragility

JOURNAL=Frontiers in Materials

VOLUME=6

YEAR=2019

URL=https://www.frontiersin.org/journals/materials/articles/10.3389/fmats.2019.00103

DOI=10.3389/fmats.2019.00103

ISSN=2296-8016

ABSTRACT=<p>The report presents the evidence for the hypothetically “universal” previtreous behavior of the pressure related apparent fragility: <inline-formula><mml:math id="M1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow><mml:mi>m</mml:mi></mml:mrow><mml:mrow><mml:mi>T</mml:mi></mml:mrow></mml:msub><mml:mrow><mml:mo stretchy="false">(</mml:mo><mml:mrow><mml:mi>P</mml:mi></mml:mrow><mml:mo stretchy="false">)</mml:mo></mml:mrow><mml:mi>∞</mml:mi><mml:mn>1</mml:mn><mml:mo>/</mml:mo><mml:mrow><mml:mo stretchy="false">(</mml:mo><mml:mrow><mml:msup><mml:mrow><mml:mi>P</mml:mi></mml:mrow><mml:mrow><mml:mo>*</mml:mo></mml:mrow></mml:msup><mml:mo>-</mml:mo><mml:mi>P</mml:mi></mml:mrow><mml:mo stretchy="false">)</mml:mo></mml:mrow></mml:math></inline-formula>, where <italic>P</italic><sup>*</sup> is the extrapolated singular pressure. This finding was the basis for deriving the “model-free” dependence for the pressure evolution of the structural relaxation time: <inline-formula><mml:math id="M2" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>τ</mml:mi><mml:mrow><mml:mo stretchy="false">(</mml:mo><mml:mrow><mml:mi>P</mml:mi></mml:mrow><mml:mo stretchy="false">)</mml:mo></mml:mrow><mml:mo>=</mml:mo><mml:msubsup><mml:mrow><mml:mi>τ</mml:mi></mml:mrow><mml:mrow><mml:mi>o</mml:mi></mml:mrow><mml:mrow><mml:mi>P</mml:mi></mml:mrow></mml:msubsup><mml:msup><mml:mrow><mml:mrow><mml:mo stretchy="false">(</mml:mo><mml:mrow><mml:msup><mml:mrow><mml:mi>P</mml:mi></mml:mrow><mml:mrow><mml:mo>*</mml:mo></mml:mrow></mml:msup><mml:mo>-</mml:mo><mml:mi>P</mml:mi></mml:mrow><mml:mo stretchy="false">)</mml:mo></mml:mrow></mml:mrow><mml:mrow><mml:mo>-</mml:mo><mml:mtext>Ψ</mml:mtext></mml:mrow></mml:msup></mml:math></inline-formula>. All these led to the new way of testing the dynamic crossover phenomenon via 1/<italic>m</italic><sub><italic>T</italic></sub> (<italic>P</italic>) vs. <italic>P</italic> plot. Finally, the behavior of electric conductivity in the previtreous domain is discussed. The experimental evidence covers 8<sup>*</sup>OCB (liquid crystal), EPON 828 (resin), diisobutyl phthalate, and propylene carbonate (low molecular weight liquids). Experiments were carried up to extreme <italic>P</italic>~ 2.2 GPa, in the “bulk” measurement capacitor. This report also contains a summary of existing descriptions of the pressure evolution of structural relaxation time or viscosity on approaching the glass transition.</p>