Block Copolymers

Definition

A block copolymer is a linear arrangement of blocks of varying monomer composition. The nomenclature for a diblock is poly-A-block-poly-B, and for a triblock is poly-A-block-poly-B-block-poly-A. It is generally described as amphiphilic (“having love for both”) or amphipathic (“having feeling for both”). A block copolymer which has hydrophobic and hydrophilic components in the same molecule cannot be amphiphilic. Block copolymers usually exhibit phase separation, which gives rise to a dispersed phase consisting of one block type in a continuous matrix of the second block type. Block copolymers show surface activity, elasticity, and impact modification. Dilute solutions of block copolymers can be investigated in solvents common to both blocks to determine their conformational behavior. More interesting is their behavior in a solvent which is a nonsolvent for one block and a good solvent for the other. Because of their unusual physical properties, several classes of block...