The synthesis of functional star copolymers as an illustration of the importance of controlling polymer structures in the design of new materials

Several different methods for the synthesis of star copolymers employing atom transfer radical polymerization are presented. They include core-first and arm-first methods, and a combination of both to prepare mikto-arm stars. Stars with a well-defined number of arms were prepared by using a core with a precise number of functional groups, and ill-defined stars were prepared from hyperbranched cores. In addition, end-functional stars were prepared by either displacing end-functional halogens or through radical addition with unreactive functional alkenes. Another approach to end-functional stars employs functional initiators and the subsequent coupling of the end-functional arms with difunctional vinyl monomers. Star-like backbones were also used to grow star-like macromolecular brushes that were visualized by AFM. The polydispersities of individual arms and entire stars followed Schulz-Flory statistics.