Solvent-Selective Reactions of Alkyl Iodide with Sodium Azide for Radical Generation and Azide Substitution and Their Application to One-Pot Synthesis of Chain-End-Functionalized Polymers

Herein, a new reaction of an alkyl iodide (R–I) with an azide anion (N₃^–) to reversibly generate the corresponding alkyl radical (R^•) is reported. Via this new reaction, N₃^– was used as an efficient catalyst in living radical polymerization, yielding a well-defined polymer–iodide. A particularly interesting finding was the solvent selectivity of this reaction; namely, R–I and N₃^– generated R^• in nonpolar solvents, while the substitution product R–N₃ was generated in polar solvents. Exploiting this unique solvent selectivity, a one-pot synthesis of polymer–N₃ was attained. N₃^– was first used as a catalyst for living radical polymerization in a nonpolar solvent to produce a polymer–iodide and was subsequently used as a substitution agent in a polar solvent by simply adding the polar solvent, thereby transforming the polymer–iodide to polymer–N₃ in one pot. This one-pot synthesis was further applied to obtain N₃-chain-end-functionalized polymer brushes on the surface, uniquely controlling the N₃ coverage (number density). Using the chain-end N₃, the obtained linear and brush polymers were connected to functional molecules via an azide–alkyne click reaction. The attractive features of this system include facile operation, access to unique polymer designs, and no requirement for using excess NaN₃. In addition to N₃^–, thiocyanate (⁻SCN) and cyanate (⁻OCN) anions were also studied

Biocompatible Choline Iodide Catalysts for Green Living Radical Polymerization of Functional Polymers

Herein, nontoxic and metabolizable choline iodide analogues, including choline iodide, acetylcholine iodide, and butyrylcholine iodide, were successfully utilized as novel catalysts for “green” living radical polymerization (LRP). Through the combination of several green solvents (ethyl lactate, ethanol, and water), this green LRP process yielded low-polydispersity hydrophobic, hydrophilic, zwitterionic, and water-soluble biocompatible polymethacrylates and polyacrylates with high monomer conversions. Well-defined hydrophobic–hydrophilic and hydrophilic–hydrophilic block copolymers were also synthesized. The accessibility to a range of polymer designs is an attractive feature of this polymerization. The use of nontoxic choline iodide catalysts as well as green polymerization conditions can contribute to sustainable polymer chemistry

Synthesis of Highly Reactive Polymer Nitrile <i>N</i>‑Oxides for Effective Solvent-Free Grafting

A one-pot synthesis of polymer nitrile <i>N</i>-oxides was achieved via the Michael addition of living polymer anions derived from vinyl monomers to commercially available <i>trans</i>-β-nitrostyrene and subsequent dehydration with concd H₂SO₄. The polymer nitrile <i>N</i>-oxides are effective as grafting agents in catalyst- and solvent-free 1,3-dipolar cycloadditions to unsaturated-bond-containing polymers with high conversion and exhibit higher reactivity compared to that of nitrile <i>N</i>-oxides prepared from 1,1-diphenylnitroethene. Application to the preparation of a functional glass surface was demonstrated using P<i>t</i>BMA nitrile <i>N</i>-oxide as a grafting agent