Designer macromolecules provide a platform by which to generate structured, multifunctional materials with tailored biochemical, redox, and optoelectronic properties. Furthermore, the solution-processable nature of functional polymers allows for device fabrication procedures that are compatible with high-throughput (e.g., roll-to-roll coating) manufacturing processes. As such, these macromolecules offer the promise of providing made-to-order, low-cost materials solutions to some of the most pressing polymer and soft materials challenges facing the world today. We will discuss two distinct classes of functional macromolecules with tuned chemistries for implementation into separation systems and organic electronic applications. In the first of these efforts, we describe the synthesis, molecular characterization, and the solid-state electronic device application of an emerging class of transparent conducting macromolecules, radical polymers. Radical polymers are macromolecular materials that have flexible polymeric backbones and pendant groups that bear stable open-shell moieties. In contrast to almost all other optoelectronically-active polymers, radical polymers lack backbone conjugation and are completely amorphous in the solid state. Despite this shift in macromolecular design archetype, we demonstrate that the solid-state electrical conductivity of a designer radical polymer exceeds 20 S m‑1, and this places this non-conjugated polymer conductor in the same regime as many grades of common commercially-available, chemically-doped conjugated conducting polymers. Thus, this work presents an alternate design paradigm for next-generation organic electronic materials, and we show their utility in myriad device archetypes with an emphasis on recent results in the realm of next-generation flexible and stretchable bioelectronics. In the second of these efforts, either A-B-C triblock polymers or A-B diblock polymers are generated using controlled radical polymerization techniques. By tuning the molecular weight, molecular weight distribution, block polymer chemical composition, and casting techniques employed, we generate mechanically-robust nanoporous thin films that are well-suited for nanofiltration and membrane adsorber applications. In fact, high-flux separations (i.e., at permeabilities equal to or greater than current commercial membranes) of particles down to ~1 nm in diameter are presented. Additionally, we demonstrate that, through the appropriate selection of the block polymer moieties, the chemistry of the nanopore walls can be tuned to any number of functional groups. In this way, we demonstrate that membranes cast from these materials separate ionic species of similar size. Moreover, these membranes remove >99% of myriad heavy metal cations from aqueous solutions in a manner that is independent of the background electrolyte. Therefore, these tailored macromolecules provide an excellent handle by which to generate size-selective and chemically-selective separations devices.