Free volumes in polystyrene probed by positron annihilation

✍ Scribed by Megumi Ban; Michihisa Kyoto; Akira Uedono; Takao Kawano; Shoichiro Tanigawa

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 525 KB
• Volume: 34
• Category: Article
• ISSN: 0887-6266
• DOI: 10.1002/(sici)1099-0488(199605)34:7<1189::aid-polb2>3.0.co;2-r

✦ Synopsis

Free volume characteristics in three samples of monodisperse polystyrene were investigated by positron annihilation technique over a temperature range from 300 to 380 K. The numberaverage 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, r3, was associated with the pick-off annihilation of ortho-positronium (0-Ps) trapped by free volumes. The change of the temperature coefficient of 73 was observed at around 350 K, at which the value of r3 was a constant value of 2.3 ns for all specimens with different molecular weights. There was no discrete change of r3 in intensity, which is corresponding to the number of free volumes. The size of free volume a t glass transition was evaluated to be 0.1 nm3.