Free volumes in polystyrene probed by positron annihilation
1996; Wiley; Volume: 34; Issue: 7 Linguagem: Inglês
10.1002/(sici)1099-0488(199605)34
ISSN1099-0488
AutoresM. Ban, Michihisa Kyoto, Akira Uedono, Takao Kawano, Shoichiro Tanigawa,
Tópico(s)Polymer crystallization and properties
ResumoFree volume characteristics in three samples of monodisperse polystyrene were investigated by positron annihilation technique over a temperature range from 300 to 380 K. The number-average molecular weight of the samples ranged from 5730 to 1,524,000. The observed lifetime spectra were resolved into three components, where the longest lifetime, τ3 was associated with the pick-off annihilation of ortho-positronium (o-Ps) trapped by free volumes. The change of the temperature coefficient of τ3 was observed at around 350 K, at which the value of τ3 was a constant value of 2,3 ns for all specimens with different molecular weights. There was no discrete change of τ3 in intensity, which is corresponding to the number of free volumes. The size of free volume at glass transition was evaluated to be 0.l nm3. © 1996 John Wiley & Sons, Inc.
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