Abstract
This theory determines the dependence of the Huggins coefficient kH on the interaction potential between rigid spheres. Hard-sphere interactions represent a minimum, with kH increasing for either attractive or longer-range repulsive potentials. Although derived for model potentials, the sticky sphere for short-range attractions and the excluded shell for repulsions, the results for kH, when plotted against A2NA/Mw[η], should characterize other potentials as well. Furthermore, this interpretation should distinguish the effects of interaction potentials from those of anisotropy or permeability of the individual particles.