Methods are described for the preparation of fiber-like nanomaterials that mimic the multilayer structure of organic electronic devices on individual polymer chains. By combining Cu(0) reversible-deactivation radical polymerization (RDRP) and ring-opening metathesis polymerization (ROMP), multiblock bottle-brush copolymers are synthesized from ordered sequences of organic semiconductors. Narrowly dispersed fibers are prepared from materials commonly used as the hole transport, electron transport, and host materials in organic electronics, with molecular weights exceeding 2 x 10(6) Da and dispersities as low as 1.12. Diblock nanofibers are then synthesized from pairs of semiconducting building blocks, giving nanostructures analogous to p-n junctions that exhibit the reversible electrochemistry of their individual parts. Finally, this strategy is used to construct nanofibers with the structure of phosphorescent organic light-emitting diodes (OLEDs) on single macromolecules, such that the photophysical properties of each component of an OLED can be independently observed. These multiblock nanofibers can be formed from arbitrary organic semiconductors without the need for crystallinity, selective solvation, or supramolecular interactions, providing powerful methods for the miniaturization of materials for organic devices.