Effect of volume changes on segmental relaxation in siloxane polymers.
From dielectric relaxation and equation-of-state measurements on polymethylphenylsiloxane and polymethyltolylsiloxane, the relative contributions of volume and thermal energy to the temperature dependence of the segmental relaxation times are quantified. In both polymers, volume exerts a substantial effect, being almost as significant as thermal energy. A possible consequence of this prominent role of volume in governing the segmental dynamics is the finding that the relaxation times, measured for a series of temperature at various (fixed) pressures, can be expressed as a single function of the volume normalized by the volume at the glass transition temperature. A similar result is found for the (isothermal) relaxation times measured at various pressures.
Paluch
M
M
Institute of Physics, Silesian University, Uniwersytecka 4, 40-007 Katowice, Poland.
Casalini
R
R
Patkowski
A
A
Pakula
T
T
Roland
C M
CM