A study of the infinite frequency longitudinal modulusMinfin;of 5P4E lsqb;mhyphen;bis(mhyphen;phenoxyphenoxy) benzenersqb; as a function of pressure, by means of the Brillouin light scattering technique, through the glass transition, is presented. To make measurements in different compression kinetics, the analysis system has been modified to reduce significantly the measuring time without lowering the signalhyphen;tohyphen;noise ratio. It is observed that theMinfin;value depends on the pressure histories and consequently contains information on the nonequilibrium structural state of the fluid. For example, when the compression rate for a step pressure from 0.17 to 0.245 GPa is divided by 30, the Brillouin shift decreases by 200 MHz, which is much larger than the experimental errors. The experimental results, obtained in various dynamic conditions similar to those encountered in an elastohydrodynamic (EHD) contact, are in relatively good agreement with computed values using a fictive pressure model. The computed structural relaxation time of the fluid is found to be strongly dependent on the compression rate. This behavior is in agreement with the large viscosity variation as a function of the transit time in an EHD contact.
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