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Experimental free volume aspects of the polymer rheology as obtained by positron annihilation lifetime spectroscopy
Author(s) -
Bartoš Josef,
Krištiak Jozef,
Šauša O.,
Bandžuch P.,
Zrubcová J.
Publication year - 2000
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/1521-3900(200008)158:1<111::aid-masy111>3.0.co;2-n
Subject(s) - materials science , glass transition , volume (thermodynamics) , polybutadiene , volume fraction , polymer , positron annihilation , rheology , atmospheric temperature range , positron , spectroscopy , thermodynamics , positron annihilation spectroscopy , annihilation , composite material , copolymer , physics , nuclear physics , quantum mechanics , electron
The ortho‐positronium (o‐Ps) annihilation parameters, i.e. the mean o‐Ps lifetime, τ 3 , and the o‐Ps relative intensity, I 3 , in cis‐1,4‐polybutadiene (cis‐1,4‐PBD) and polyisobutylene (PIB) over a wide temperature range including the glass‐liquid transition have been measured by means of positron annihilation lifetime Spectroscopy (PALS). From them the free volume microstructural characteristics, i.e. the mean free volume hole size, V h , and the free volume hole fraction, f h , have been determined via a semiempirical quantum‐mechanical model of o‐Ps in a spherical hole or a phenomenological model of volumetric and free volume hole properties, respectively. Consequently, the literature rheological data for both the above‐mentioned polymers have been related to the free volume hole fractions via the WLF‐Doolittle type equation. It has been found that i) in the case of PIB this equation holds over 130K above the glass transition temperature T g and ii) in the case of cis‐PBD the WLF‐Doolitle equation is valid in the temperature range over 60K above 1.3T g , but below 1.3T g down to T g the modified WLF‐Doolittle‐Macedo‐Litovitz equation with the additional activation‐energy term describes the shift factor data better.