The Components of Activation Entropy of -Relaxation
in Linear Polymers

G. M. Bartenev

Institute of Physical Chemistry, Russian Academy of Sciences, Leninskii pr. 31, Moscow, 117915 Russia

Received April 2, 1998;
Revised Manuscript Received July 27, 1998

Abstract—Molecular and thermodynamic analysis of the -relaxation process in linear flexible-chain poly-
mers was carried out. This analysis is based on the dual molecular mechanism of segmental mobility and allows
one to obtain quantitative estimates of the two components of activation entropy S* = S₁ + S₂. The roles of
both components in the glass transition process are discussed. It was found that the first component S₁ is nega-
tive, and this component is associated with the transition of a segment from a basic to oriented state (the con-
formational mechanism of segmental mobility). On the contrary, the second component S₂ is positive, and this
component is related to the development of the fluctuation free volume in the correlation volume, into which a
segment is moved (the translational mechanism of segmental mobility). The value of S₁ [~ 10 J/(mol K)] is
independent of temperature and provides the contribution to the pre-exponential coefficient B of the charac-
teristic relaxation time of -relaxation. As compared with the corresponding coefficient B of -relaxation,
B increases by about 40 times. Component S₂ depends on temperature and contributes to the effective activa-
tion energy of -relaxation, which equals 5–10% of the activation energy U. Hence, the activation entropy
slightly affects the kinetics of the -relaxation of linear polymers.

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