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Positron Annihilation in Norbornene‐Ethylene Copolymers
Author(s) -
Djourelov Nikolaj,
Misheva Marijka,
Zamfirova Galina,
Benavente Rosario,
Pérez Ernesto,
Pereña José M.
Publication year - 2003
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.200350014
Subject(s) - norbornene , copolymer , glass transition , amorphous solid , materials science , polymer chemistry , ethylene , positron , positron annihilation spectroscopy , metallocene , methylaluminoxane , relaxation (psychology) , positron annihilation , chemistry , polymerization , crystallography , catalysis , polymer , composite material , organic chemistry , physics , nuclear physics , psychology , social psychology , electron
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.