The equation of state of polymers. Part III: Relation with the compensation law
Laboratoire de Physique des Solides, CNRS, Université de Paris-Sud, 91405, Orsay, France
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Accepted: 21 August 2017
Published online: 29 September 2017
The properties of amorphous polymers and of organic compounds under pressure are interpreted in the framework of the modified Van der Walls Equation of State (mVW-EOS) the Vogel-Fulcher-Tamann (VFT) law and of the compensation law. We have shown recently that polymers and organic compounds in amorphous liquid and crystalline states verify the mVW-EOS which depends on three parameters, and . In this paper we compare the characteristic pressure of the mVW-EOS to the various pressures deduced from thermodynamic and kinetic properties of polymers in the liquid and solid states. and are: a) the enthalpy and volume change at the melting and glass transitions (the glass being isotropic or oriented and annealed below at various aging conditions); b) the activation parameters of individual and cooperative motions in crystalline liquid and amorphous polymers studied by dielectric or mechanical spectroscopy; and c) the activation parameters of amorphous (solid and liquid) polymers submitted to a deformation depending on the time frequency temperature and strain rate. For a same material, whatever its state and whatever the experimental properties analyzed (dielectric and mechanical relaxation, viscosity, auto-diffusion, yielding under hydrostatic pressure), we demonstrate that , ( Grüneisen parameter, compressibility). In all polymers and organic compounds (and water), these pressures, weakly dependent on T and P near and at low pressure are characteristic of the H-H inter-molecular interactions. It is shown that the two empirical Lawson and Keyes relations of the compensation law can be deduced from the mVW-EOS.
Key words: Soft Matter: Polymers and Polyelectrolytes
© EDP Sciences, SIF, Springer-Verlag GmbH Germany, 2017