8 - Gradients in Homopolymers, Blends, and Copolymers

Abstract

In homopolymers with additives, blends, and copolymers, synergism can be accomplished in the structure/property/cost relationships if a proper gradient in components compositions is reached. Here, a description of gradients that can be formed in those materials is shown, briefly describing the methods used to obtain gradients in homopolymers. The core of this chapter is devoted to the formation of gradients in multicomponent polymer systems (MPSs) (polymer blends and copolymers), presenting the methods of preparation, the properties that can be obtained, and the advantages of such types of polymeric materials with respect to those containing uniform composition in the polymer bulk. The evolution of blends to make gradient interpenetrating polymer networks, and the synthesis of gradient copolymers represent nowadays the way to prepare tailormade MPSs when searching for specific properties. To design the properties of gradient copolymers, the change in chains composition as the conversion proceeds can be used in the controlled radical polymerization reaction scheme. Alternatively, the weight distribution of copolymer chains composition of the polymer bulk can be used (presented here for gradient copolymers formed by traditional radical polymerization) to design and interpret the mechanical and thermal behavior of the gradient copolymers.