Open spaces and molecular motions of polyether-based network polymers probed by positron annihilation

✍ Scribed by A. Uedono; S. Tanigawa; M. Watanabe; A. Nishimoto

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 156 KB
• Volume: 36
• Category: Article
• ISSN: 0887-6266
• DOI: 10.1002/(sici)1099-0488(199808)36:11<1919::aid-polb13>3.0.co;2-a

✦ Synopsis

The lifetimes of positrons have been measured for network polymers based on polyethers. From the temperature dependence of the lifetime of ortho-positronium (o-Ps), t 3 , for the network polymer of poly(ethylene oxide-co-propylene oxide) [P(EO/ PO)], an onset temperature for limited local motions of molecules, T g , and the glass transition temperature, T g , were determined to be 57 and 201 K, respectively. For the network polymer of poly[EO-co-2-(2-methoxyethoxy)ethyl glycidyl ether] [P(EO/ MEEGE)], T g and T g were determined to be 57 and 185 K, respectively. For both specimens, above 270 K, the observed linear temperature dependence of t 3 was attributed to the thermal expansion of open spaces in a liquid state. In the temperature range between T g and 270 K, for the P(EO/MEEGE) network, t 3 was longer and its intensity was smaller than those for the P(EO/PO) network. These results were attributed to the increase in the size of open spaces for the P(EO/MEEGE) network polymer and the blocking of these regions by motions of side chains and chain ends.