Progress in control of microdomain orientation in block copolymers - Efficiencies of various external fields

Recent progresses in control of orientation for block copolymer microdomains using external fields, such as force fields, electric fields, and magnetic fields will be reviewed. Since it has been more recognized that such explicit external fields are not necessarily required, implicit (unconscious) external fields, which mean those imposed automatically onto block copolymers, irrespective of intention, will also be covered under categories of “surface fields” and “directional fields”, where self-organizing abilities of block copolymers are utilized for performance of spontaneous orientation (or in other words self-orientation). Although some of these phenomena of the self-orientation have been already used in application-oriented researches towards nanotechnology, the mechanisms of self-orientation still remain ambiguous. Moreover, although there have been reported interesting and significant findings on the self-orientation in the recent decades, it cannot be stated that the individual findings are well correlated with each other to draw formulated cognition. Therefore, in this feature article, we systematically discuss them under the new categories of the implicit external fields for a better understanding of phenomena and hopefully mechanisms of microdomain orientation.