Polymer-Melt Viscosity and the Glass Transition: An Evaluation of the Adam–Gibbs and the Free-Volume Models
1968; American Institute of Physics; Volume: 49; Issue: 3 Linguagem: Inglês
10.1063/1.1670237
ISSN1520-9032
Autores Tópico(s)Polymer crystallization and properties
ResumoThe Adam–Gibbs and the free-volume theories of polymer-melt viscosity and the glass transition are applied to the infinite polymethylene chain by comparing the exponential terms in the respective viscosity equations: 2.3B / (T − T0) = C / TSc = b / φ. It is shown that the configurational entropy Sc and the free volume φ, which apply in these equations, constitute only a portion of the thermodynamic “excess” liquid entropy and volume. In an alternate form of the A–G equation: C / TSc = Δμz* / RT, if Δμ is identified as 2.3BR, zg* turns out to be equal to the “activation volume” expressed as monomer segments at Tg. In the Adam–Gibbs context, the glass transition is assumed to be characterized by the constant: zg*Scg = 5.5 e.u. On this basis, a value of Sc is derived for polystyrene at Tm which agrees with independent estimates. Values of the A–G and the free-volume parameters are reported for (CH2)∞, polystyrene, and polyisobutylene, and relationships between Sc and φ are presented.
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