4. Polymer blends

Mixing polymers of different chemical natures with a view to developing original polymeric materials is a highly attractive approach. Materials science offers many examples of – alloys, particularly of – metals, whose properties are far superior to those of the starting compounds. What's more, developing an original material from a mixture of polymers seems, at first sight, less costly and less random than synthesizing an unknown polymer from a new monomer.

Unfortunately, experimental evidence belies this simplistic view, because in most cases, the prevailing rule in the field of polymers is that of the immiscibility of macromolecular entities of different chemical natures. The incompatibility of polymers with one another leads to their demixing, and is the main cause of the mediocre properties that characterize most polymer blends. At best, incompatible blends...