Here m is the molecular mass, is the mass density, and the omegas are functions of , and and are parameters in the inter-molecular force expression. If the omegas are set equal to 1, then the results above are those for a gas of rigid spheres of diameter .
2. POLYMER MIXTURES
This discussion is a summary of a series of publications by Curtiss and Bird during the period 1996 to 1999, in which we tried, as much as possible, to parallel the above discussion for dilute gas mixtures . We visualize a polymer molecule as a collection of mass-points ("beads") connected by some kind of interbead forces ("springs"). The springs may be chosen in several different ways:
This is a simple linear spring, which can be stretched
indefinitely. It is easy to handle analytically, but gives
generally poor results for describing rheological behavior.
H is a spring constant.