Relaxation processes of hydrogen bonded species in a polystyrene matrix

1978 ◽  
Vol 74 (0) ◽  
pp. 2045 ◽  
Author(s):  
Jagdish P. Shukla ◽  
Stanley Walker ◽  
John Warren
Keyword(s):  
Relaxation Processes ◽  
Polystyrene Matrix ◽  
Hydrogen Bonded

scholarly journals A microscopic look at the Johari-Goldstein relaxation in a hydrogen-bonded glass-former

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
F. Caporaletti ◽  
S. Capaccioli ◽  
S. Valenti ◽  
M. Mikolasek ◽  
A. I. Chumakov ◽  
...  
Keyword(s):  
Time Domain ◽  
Glassy State ◽  
Center Of Mass ◽  
Relaxation Processes ◽  
Undercooled Liquid ◽  
Microscopic Scale ◽  
Glass Forming ◽  
Full Explanation ◽  
Molecular Scale ◽  
Hydrogen Bonded

Abstract Understanding the glass transition requires getting the picture of the dynamical processes that intervene in it. Glass-forming liquids show a characteristic decoupling of relaxation processes when they are cooled down towards the glassy state. The faster (βJG) process is still under scrutiny, and its full explanation necessitates information at the microscopic scale. To this aim, nuclear γ-resonance time-domain interferometry (TDI) has been utilized to investigate 5-methyl-2-hexanol, a hydrogen-bonded liquid with a pronounced βJG process as measured by dielectric spectroscopy. TDI probes in fact the center-of-mass, molecular dynamics at scattering-vectors corresponding to both inter- and intra-molecular distances. Our measurements demonstrate that, in the undercooled liquid phase, the βJG relaxation can be visualized as a spatially-restricted rearrangement of molecules within the cage of their closest neighbours accompanied by larger excursions which reach out at least the inter-molecular scale and are related to cage-breaking events. In-cage rattling and cage-breaking processes therefore coexist in the βJG relaxation.

Dielectric relaxation processes of some dialkyl disulfides

1983 ◽  
Vol 61 (9) ◽  
pp. 2107-2111 ◽  
Author(s):  
H. A. Khwaja ◽  
S. Walker
Keyword(s):  
Dielectric Relaxation ◽  
Relaxation Processes ◽  
Alkyl Chains ◽  
Polystyrene Matrix ◽  
Segmental Relaxation ◽  
Higher Temperature ◽  
Dialkyl Disulfides ◽  
Intramolecular Rotation ◽  
Two Temperature ◽  
Low Temperature Process

Dielectric relaxation studies have been performed for dimethyl, diethyl, di-isopropyl, di-n-butyl, di-tert-butyl, and di-n-octyl disulfides in a polystyrene matrix. For the last five compounds the absorption appears in two temperature regions. The relaxation data for the higher temperature regions are consistent with intramolecular rotation around the S—S bond with accompanying flexibility in the alkyl chains. The enthalpy barrier to this relaxation process is ~29 kJ mol−1 and is the trans (lower) barrier. This value is typical for all six dialkyl disulfides. The most likely interpretation of the low temperature process is that there is segmental relaxation of the alkyl chains which also involves movement of the main dipoles (S—S and S—C).

Relaxation processes of some aromatic sulfides, sulfoxides, and sulfones in a polystyrene matrix

1980 ◽  
Vol 73 (7) ◽  
pp. 3460-3466 ◽  
Author(s):  
M. A. Desando ◽  
S. Walker ◽  
W. H. Baarschers
Keyword(s):  
Relaxation Processes ◽  
Polystyrene Matrix
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