From the general definition, the radius of gyration can be calculated as the root mean square distance of the objects' parts from either a given axis or its centre of gravity. In particular, it can be referred to as the radial... [ view full abstract ]

From the general definition, the radius of gyration can be calculated as the root mean square distance of the objects' parts from either a given axis or its centre of gravity. In particular, it can be referred to as the radial distance from a given axis at which the mass of a body could be concentrated without altering the rotational inertia of the body about that axis. For a planar distribution of mass rotating about some axis in the plane of the mass, the radius of gyration can be considered as the equivalent distance of the mass from the axis of rotation. Radius of gyration plays an important role in the polymers chemistry: it is well known that for a polymer in a poor solvent, the radius of gyration is smaller than in a good solvent. In a fact, the radius of gyration is usually a better estimate of the chain dimensions than the root-mean-squared end-to-end distance, as it accounts for the hydrodynamic interactions between the polymer chains and the solvent. The end-to-end distance is difficult to measure, while the radius of gyration can be measured by a light scattering technique.

It is worthwhile to investigate this matter, in order to provide a more thorough explanation as to how the thermophysical properties, i.e. surface tension, thermal conductivity and dynamic viscosity, are related to the radius of gyration.

During the thermophysical properties prediction/correlation, the critical parameters are adopted when the corresponding states principle is applied. The starting point is that the parameters at the critical point, namely critical temperature, critical pressure and critical density, show to be well related to radius of gyration for almost all the organic and inorganic fluids. These relationships were explored as a starting point.

As a second step, new equations for the surface tension, the dynamic viscosity and the thermal conductivity description adopting the radius of gyration as a main parameter are presented.