An obvious trend in the Center’s activities the past year has been experimental measurements and analyses related to multi-component systems. This common theme has arisen from the diverse needs of our Partners. The work has ranged from experimental diffusivity and solubility measurements to the correlation and theoretical predictions of the multi-component interactions of two or more solvents in a polymer. The theoretical developments related to the thermodynamics of multi-component systems are presents in Chapters IV, V, XIII, and XIV. Related experimental work concerned with multi-component diffusion and thermodynamics are presented in Chapters IX, X, XIII, and XIV.