Liquid theory applied to quantum liquid helium-3 and molten high polymers

Abstract

The significant structure theory of liquids is successfully applied to the quantum liquid $He^3$ and molten high polymers. In applying the theory to the liquid $He^3$, the partition function uses the Debye partition function for the solid-like molecules and the Fermi-Dirac partition function for the gas-like degrees of freedom. To evaluate the gas-like partition function, numerical calculations are performed and some integral functions appearing in the equation of state of the ideal Fermi-Dirac gas are tabulated. In the solid-like molecules, the molar volume Vs depends on the temperature, and a linear dependence is used. The thermodynamic properties, such as molar volume, vapor pressure, entropy, heat capacity, boiling point properties, and the critical constants as well as the surface tension of liquid $He^3$ are calculated. The agreement between theory and experiment is satisfactory. In applying the theory to the molten high polymers, the repeating constituent groups are regarded as point interaction centers. The configurational energy of a chain constituent group is evaluated assuming a short-range parallel alignment of chain constituent groups and using Lennard-Jones (6-12) potential. The theory provides a semi quantitative method for predicting the surface and interfacial tensions of molten high polymers. The additional inclusion of polar force interaction besides the dispersion force interaction gives a better agreement between the calculated and observed interfacial tensions for the polymers whose constituent groups have permanent dipole moments. But the surface tension is nearly unaffected by the polar force interaction.