Positron Annihilation in Norbornene-Ethylene Copolymers

✍ Scribed by Nikolaj Djourelov; Marijka Misheva; Galina Zamfirova; Rosario Benavente; Ernesto Pérez; José M. Pereña

• Publisher: John Wiley and Sons
• Year: 2003
• Tongue: English
• Weight: 125 KB
• Volume: 204
• Category: Article
• ISSN: 1022-1352
• DOI: 10.1002/macp.200350014

✦ Synopsis

Abstract

Norbornene‐ethylene amorphous copolymers with high content in norbornene are obtained with metallocene catalysts and present a high glass transition temperature. The size and concentration of the free‐volume holes of these copolymers, which affect to their gas barrier properties, has been studied by positron annihilation lifetime spectroscopy. The results of positron annihilation studies have shown that the microstructure of all samples is similar and they can be related to the dynamic mechanical parameters (temperatures and activation energies of the relaxations) as well as to the stress‐strain characteristics and microhardness of the copolymers. Moreover, it has been shown that in the case of the norbornene‐ethylene copolymers investigated the influence of the molecular rigidity on the glass transition temperature prevails over that of the pore dimensions.

Apparent activation energies and reciprocal values of tan δ for the γ relaxation as functions of volumes of the holes determined at T~g~ −50 °C.

magnified imageApparent activation energies and reciprocal values of tan δ for the γ relaxation as functions of volumes of the holes determined at T~g~ −50 °C.