Light-Scattering Study of the Glass Transition in Lubricants

1978 ◽  
Vol 100 (3) ◽  
pp. 418-422 ◽  
Author(s):  
M. A. Alsaad ◽  
W. O. Winer ◽  
F. D. Medina ◽  
D. C. O’Shea
Keyword(s):  
Phase Diagram ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Light Scattering ◽  
Brillouin Scattering ◽  
Maximum Pressure ◽  
Scattering Study ◽  
Temperature And Pressure

The sound velocity of four lubricants has been measured as a function of temperature and pressure using Brillouin scattering. A change in slope of the velocity as a function of temperature or pressure allowed the determination of the glass transition temperature and pressure. The glass transition data were used to construct a phase diagram for each lubricant. The data indicate that Tg increased with pressure at a rate which ranged from 120 to 200 C/GPa. The maximum pressure attained was 0.69 GPa and the temperature range was from 25 to 100 C.

Brillouin Light Scattering Determination of the Glass Transition in Thin, Freely-Standing Poly(styrene) Films

1995 ◽  
Vol 407 ◽  
Author(s):  
J. A. Forrest ◽  
K. Dalnoki-Veress ◽  
J. R. Dutcher ◽  
A. C. Rowat ◽  
J. R. Stevens
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Light Scattering ◽  
Guided Waves ◽  
Brillouin Light Scattering ◽  
Scanning Calorimetry ◽  
Force Microscopy ◽  
Glass Substrates

ABSTRACTWe have used Brillouin light scattering (BLS) to measure the glass transition temperature of thin, freely-standing poly(styrene) (PS) films. The freely-standing films were prepared by spincoating solutions of PS in toluene onto glass substrates, annealing the supported films in vacuum, and then using a water surface transfer technique to place the films across a 3 mm diameter orifice. Ellipsometry measurements of similar floated films transferred to Si(001) wafers allow the determination of the film thicknesses. Atomic force microscopy measurements revealed that the films have an rms roughness of less than 10 A˚. With the freely-standing films placed in an optical furnace, we performed BLS measurements of the films using a high-contrast, multipassed, tandem Fabry-Perot interferometer. We obtained a reliable, reproducible measure of the glass transition temperature, Tg, from the large changes in the frequencies of the thermally-excited, viscoelastic, film-guided waves within the PS films as the films were heated above Tg. BLS results for bulk PS and a 1800 A˚ thick, freely-standing PS film are presented. We find the same glass transition temperature for the 1800 A˚ thick film as the bulk PS sample. This Tg value is the same as that obtained using differential scanning calorimetry (DSC).

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