Observation of the orientational loss above the glass transition temperature in oriented polyethylene-terephthalate films using brillouin light scattering

1981 ◽  
Vol 19 (8) ◽  
pp. 1273-1275 ◽  
Author(s):  
D. B. Cavanaugh ◽  
C. H. Wang
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Light Scattering ◽  
Polyethylene Terephthalate ◽  
Brillouin Light Scattering ◽  
Oriented Polyethylene

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).

Time and Ensemble Averaged Dynamic Light Scattering in Orthoterphenyl Above and Below the Glass Transition

1996 ◽  
Vol 455 ◽  
Author(s):  
D. L. Sidebottom ◽  
C. M. Sorensen
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Light Scattering ◽  
Dynamic Light Scattering ◽  
Structural Relaxation ◽  
Mode Coupling ◽  
Average Correlation ◽  
Glass Forming ◽  
Ergodicity Breaking

ABSTRACTWhile traditional dynamic light scattering is useful for following structural relaxation in the liquid, in the glassy domain the technique is limited by the ultimate patience of the experimentalist; i.e., the structural relaxation can not be measured when the experimental time scale is less than the structural relaxation time. Nevertheless, we show how useful information regarding structural relaxation can be accessed from light scattering in the glass using a novel ensemble-averaged technique. Dynamic light scattering (DLS) measurements performed on glass forming orthoterphenyl show an inequality between time and ensemble average correlation functions near and below the calorimetrie glass transition temperature, Tg, and hence demonstrate ergodicity breaking. Our ensemble averaged measurements provide a measure of the so-called non-ergodicity parameter, fq, below Tg. Our DLS results for orthoterphenyl indicate that the functional form for fq is consistent with Mode Coupling theory predictions, but occurs at the glass transition temperature, Tg≈243K, rather than at TC≈290K as observed in neutron scattering studies.

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