Our Approaches to Block Copolymer Architectures

After a targeted polymer is synthesized, it is then used for assembly. The assembly process can include self-assembly, either in a block-selective solvent or in the solid state. In a block-selective solvent, the self-assembled structures may form micelles or singlechain micelles. In the solid state, the self-assembled structures will normally be the periodically spaced and regularly shaped domain structures that have been mentioned earlier in Section 24.2. 

Permanent and permanent sculpted nanostructures are stable architectures. They can therefore be further chemically processed to yield more complex structures. For example, we have covalently linked different stable block copolymer nanostructures to yield coupled nanostructures. The end coupling of a hydrophobic nanotube with a hydrophilic nanotube yielded an amphiphilic nanotube diblock structure (Yan et al., 2004). The attachment of hydrophobic block copolymer nanotubes by their ends to the surfaces of hydrophilic nanospheres bearing carboxyl groups yielded a supersurfactant (Liu et al., 2003). 

A nanombe diblock structure can be viewed as a macroscopic counterpart of a diblock copolymer. In block-selective solvents, a multiblock nanotube sample was shown to undergo hierarchical assembly to form supermiceUes (Yan et ai, 2004). Aside from coupled nanostructures, ordinary micelles have also been used to perform double , or hierarchical, assembly in order to yield hierarchical structures (Hu et al., 2008a). In these cases. Tier I assembly is performed using block copolymers to form micelles. At the Tier II level, the micelles are further assembled into hierarchical structures. 

Since our work on the preparation of nanostructures and hierarchical structures has been reviewed previously (Lazzari et ai, 2006 Liu, 2008), it will not be described in this chapter. Rather, we will discuss in some length, our more recent work involving the preparation of molecular architectures from block copolymer precursors. 

---