Architecture of multi-component copolymer brushes: Synthesis, solution properties and application for nanodevices

In this review article, we describe the architecture of multi-component copolymer brushes. These copolymer brushes can be classified into tree types, i.e., double-cylinder-type, prototype, and block-type. Double-cylinder-type copolymer brushes were prepared by free-radical polymerization of corresponding diblock macromonomer or by the grafting from approach using atom transfer radical polymerization (ATRP). Alternating free-radical copolymerization of the mixture of two macromonomers provided prototype copolymer brushes. ATRP was applied to the synthesis of AB-type brush-block-brush (block-type) copolymers. All copolymer brushes were molecularly dissolved in a dilute solution due to densely branched side chains and took geometrically anisotropic conformation such as cylinder with increasing aspect ratio. In self-assembly process of amphiphilic prototype copolymer brushes in water, hierarchical generations from small rods to large rods were observed, because copolymer brushes exhibited phase-separated hydrophobic/hydrophilic domains. Moreover, binding of anionic/nonionic polyeletrolyte prototype brushes with cationic linear polyelectrolyte formed an interesting complex of a high order by electrostatic interaction. On the other hand, the molecular wires in electronic nanodevices were prepared by forming conducting polypyrroles with an internal core of double-cylider-type copolymer brushes as templates, where as the outer cylinder parts play the role of an insulator.