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

✍ Scribed by A. Uedono; W. Aiko; T. Yamamoto; T. Nakamichi; S. Tanigawa

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 145 KB
• Volume: 37
• Category: Article
• ISSN: 0887-6266
• DOI: 10.1002/(sici)1099-0488(19991015)37:20<2875::aid-polb7>3.0.co;2-e

✦ Synopsis

Lifetime spectra of positrons have been measured for acrylic epoxy-based network polymers. For the specimens with the different permeability coefficients to water vapor C p , the lifetime of ortho-positronium (o-Ps) 3 increased with increasing C p . This fact suggests that the permeability increases with an increase in the size of open spaces. From measurements of temperature dependencies of 3 and the intensity of o-Ps, three onset temperatures for the change in the temperature gradient of these parameters were determined. The highest onset temperature (T ␣ ϭ 300 -325 K) was identified to be the glass transition temperature, and others (T ␥ ϭ 90 -180 K and T ␤ ϭ 160 -205 K) were associated with the onset temperatures for limited local motions of molecules; those molecular motions were found to be affected by both the number of crosslinks and the presence of free side chains.