A Versatile and Efficient Strategy to Discrete Conjugated Oligomers

An efficient and scalable strategy to prepare libraries of discrete conjugated oligomers (<i><i>Đ</i></i> = 1.0) using the combination of controlled polymerization and automated flash chromatography is reported. From this two-step process, a series of discrete conjugated materials from dimers to tetradecamers could be isolated in high yield with excellent structural control. Facile and scalable access to monodisperse libraries of different conjugated oligomers opens pathways to designer mixtures with precise composition and monomer sequence, allowing exquisite control over their physical, optical, and electronic properties

Metal-Free Removal of Polymer Chain Ends Using Light

A light-mediated method for the facile removal of polymer end groups that are common to controlled radical polymerization techniques is presented. This metal-free strategy is general, being effective for chlorine, bromine, and thiocarbonylthio moieties as well as a number of different polymer families (styrenic, acrylic, and methacrylic). In addition to solution reactions, this process is readily translated to thin films, where light mediation allows the straightforward fabrication of hierarchically patterned polymer brushes

Chemoselective Radical Dehalogenation and C–C Bond Formation on Aryl Halide Substrates Using Organic Photoredox Catalysts

Despite the number of methods available for dehalogenation and carbon–carbon bond formation using aryl halides, strategies that provide chemoselectivity for systems bearing multiple carbon–halogen bonds are still needed. Herein, we report the ability to tune the reduction potential of metal-free phenothiazine-based photoredox catalysts and demonstrate the application of these catalysts for chemoselective carbon–halogen bond activation to achieve C–C cross-coupling reactions as well as reductive dehalogenations. This procedure works both for conjugated polyhalides as well as unconjugated substrates. We further illustrate the usefulness of this protocol by intramolecular cyclization of a pyrrole substrate, an advanced building block for a family of natural products known to exhibit biological activity

Simple Benchtop Approach to Polymer Brush Nanostructures Using Visible-Light-Mediated Metal-Free Atom Transfer Radical Polymerization

The development of an operationally simple, metal-free surface-initiated atom transfer radical polymerization (SI-ATRP) based on visible-light mediation is reported. The facile nature of this process enables the fabrication of well-defined polymer brushes from flat and curved surfaces using a “benchtop” setup that can be easily scaled to four-inch wafers. This circumvents the requirement of stringent air-free environments (i.e., glovebox), and mediation by visible light allows for spatial control on the micron scale, with complex three-dimensional patterns achieved in a single step. This robust approach leads to unprecedented access to brush architectures for nonexperts

A Versatile and Scalable Strategy to Discrete Oligomers

A versatile strategy is reported for the multigram synthesis of discrete oligomers from commercially available monomer families, e.g., acrylates, styrenics, and siloxanes. Central to this strategy is the identification of reproducible procedures for the separation of oligomer mixtures using automated flash chromatography systems with the effectiveness of this approach demonstrated through the multigram preparation of discrete oligomer libraries (<i><i>Đ</i></i> = 1.0). Synthetic availability, coupled with accurate structural control, allows these functional building blocks to be harnessed for both fundamental studies as well as targeted technological applications