The origin of the Poisson ratio of amorphous organic polymers and inorganic glasses.

Studies concerning the relationship between the value of μ and a number of mechanical and thermal properties of amorphous polymers and glasses are analyzed with the aim to gain information about the origin of Poisson ratio μ in these systems. It is shown that the Poisson ratio features a more pronounced structure-sensitive behavior than the elastic modulus, although the Poisson ratio varies in a narrow range. The relationship between the Poisson ratio and the Grüneisen parameter is substantiated. In this context, the issue of the correlation between harmonic and anharmonic quantities is highlighted. The Poisson ratio is sensitive to lattice dynamics and atomic-molecular structures of polymers and glasses. When light atoms, for example, hydrogen atoms in polyethylene, are replaced with larger and heavier atoms on pendant chains of the macromolecular backbone, anharmonicity increases; that is, lattice Grüneisen parameter γ increases. As a result, the Poisson ratio increases because these quantities are related unambiguously. Conditions of preparing an isotropic material with a negative Poisson ratio (μ < 0) are discussed. The relative ultimate strain of the interatomic bond in glassy systems is a function of the Poisson ratio solely. The frozen elastic strain of amorphous polymers and glasses is likewise a single-valued function of the Poisson ratio. The discussed phenomena are interpreted in terms of the Kuz'menko and Pineda theories and the Berlin-Rothenburg-Bathurst model. [ABSTRACT FROM AUTHOR]