Effect of polymer polarity on the positronium formation

✍ Scribed by Chenze Qi; Wang Wei; Yanjie Wu; Shuihe Zhang; Wang Haijun; Hamai Li; Tianmin Wang; Fengyuan Yan

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 161 KB
• Volume: 38
• Category: Article
• ISSN: 0887-6266
• DOI: 10.1002/(sici)1099-0488(20000201)38:3<435::aid-polb9>3.0.co;2-q

✦ Synopsis

Positron annihilation lifetime spectra have been measured on styrenemethyl methacrylate, styrene-acrylonitrile, and styrene-butyl methacrylate copolymers. The results show that the longest lifetime 3 remains constant during extended PALS measurement in all experiment copolymers, and relative intensity I 3 decreases to a certain extent with measured time in weak polar copolymers and remain almost unchanged in strong polar copolymers as well as ST-BMA copolymers. The observed decrease in I 3 have been found to be unrelated to the microstructural change of copolymers, and, instead, to be more likely a result of the buildup of an electric field inside the copolymers during the prolonged PALS measurement. The field effect can result in the decrease of I 3 due to the increase in the positrons and electrons diffusing out of the spur, but the influence of the electric field on I 3 decrease with increasing the polarity of the copolymers and the softness of side groups of macromolecular chains in the copolymers.