This volume contains ten contributions which together provide an account of the various approaches used to improve the toughness of polymer matrices. The correlations among the molecular structure of the components, the morphology, and the mechanical properties of blend systems are emphasized, as are the methods used to control the structure of these materials during processing. Some topics, which are indispensable in the design and formulation of tough polymer blends, include the role of the interface in multicomponent systems, the chemical reactivity of the blend components, the mode and state of dispersion of the second phase, the crystallinity and crystallization conditions, and the glass transition temperature. Also covered is the work which began in the early 1970s with the chemical modification of ethylene-propylene copolymers to be used as tougheners of Polyamide-6. Double-spaced. B&w illustrations.