Effect of substrate interactions on the glass transition and length-scale of correlated dynamics in ultra-thin molecular glass films

2018 ◽  
Vol 149 (18) ◽  
pp. 184902 ◽  
Author(s):  
Yue Zhang ◽  
Connor N. Woods ◽  
Mauricio Alvarez ◽  
Yi Jin ◽  
Robert A. Riggleman ◽  
...  
Keyword(s):  
Glass Transition ◽  
Length Scale ◽  
Substrate Interactions ◽  
Molecular Glass ◽  
Glass Films

scholarly journals Inter-enantiomer conversion dynamics and Johari–Goldstein relaxation of benzophenones

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Michela Romanini ◽  
Roberto Macovez ◽  
Maria Barrio ◽  
Josep Lluís Tamarit
Keyword(s):  
Glass Transition ◽  
Dielectric Loss ◽  
Dielectric Spectroscopy ◽  
Parent Compound ◽  
Scanning Calorimetry ◽  
Molecular Conformations ◽  
Molecular Glass ◽  
Phenyl Ketone ◽  
Temperature And Pressure ◽  
Opposite Chirality

AbstractWe employ temperature- and pressure-dependent dielectric spectroscopy, as well as differential scanning calorimetry, to characterize benzophenone and the singly-substituted ortho-bromobenzophenone derivative in the liquid and glass states, and analyze the results in terms of the molecular conformations reported for these molecules. Despite the significantly higher mass of the brominated derivative, its dynamic and calorimetric glass transition temperatures are only ten degrees higher than those of benzophenone. The kinetic fragility index of the halogenated molecule is lower than that of the parent compound, and is found to decrease with increasing pressure. By a detailed analysis of the dielectric loss spectra, we provide evidence for the existence of a Johari–Goldstein (JG) relaxation in both compounds, thus settling the controversy concerning the possible lack of a JG process in benzophenone and confirming the universality of this dielectric loss feature in molecular glass-formers. Both compounds also display an intramolecular relaxation, whose characteristic timescale appears to be correlated with that of the cooperative structural relaxation associated with the glass transition. The limited molecular flexibility of ortho-bromobenzophenone allows identifying the intramolecular relaxation as the inter-enantiomeric conversion between two isoenergetic conformers of opposite chirality, which only differ in the sign of the angle between the brominated aryl ring and the coplanar phenyl-ketone subunit. The observation by dielectric spectroscopy of a similar relaxation also in liquid benzophenone indicates that the inter-enantiomer conversion between the two isoenergetic helicoidal ground-state conformers of opposite chirality occurs via a transition state characterized by a coplanar phenyl-ketone moiety.

scholarly journals Can the glass transition be explained without a growing static length scale?

2019 ◽  
Vol 150 (9) ◽  
pp. 094501 ◽  
Author(s):  
Ludovic Berthier ◽  
Giulio Biroli ◽  
Jean-Philippe Bouchaud ◽  
Gilles Tarjus
Keyword(s):  
Glass Transition ◽  
Length Scale

Length Scale of Cooperativity in the Dynamic Glass Transition

1997 ◽  
Vol 79 (11) ◽  
pp. 2077-2080 ◽  
Author(s):  
M. Arndt ◽  
R. Stannarius ◽  
H. Groothues ◽  
E. Hempel ◽  
F. Kremer
Keyword(s):  
Glass Transition ◽  
Length Scale

scholarly journals Long-range correlated dynamics in ultra-thin molecular glass films

2016 ◽  
Vol 145 (11) ◽  
pp. 114502 ◽  
Author(s):  
Yue Zhang ◽  
Ethan C. Glor ◽  
Mu Li ◽  
Tianyi Liu ◽  
Kareem Wahid ◽  
...  
Keyword(s):  
Long Range ◽  
Molecular Glass ◽  
Glass Films

Dynamic Heterogeneity and Cooperative Length Scale at Dynamic Glass Transition in Glass Forming Liquids

2015 ◽  
Vol 48 (22) ◽  
pp. 8219-8231 ◽  
Author(s):  
Bidur Rijal ◽  
Laurent Delbreilh ◽  
Allisson Saiter
Keyword(s):  
Glass Transition ◽  
Length Scale ◽  
Dynamic Heterogeneity ◽  
Glass Forming
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