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

Abstract

Herein, a new reaction of an alkyl iodide (R-I) with an azide anion (N) to reversibly generate the corresponding alkyl radical (R) is reported. Via this new reaction, N 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 N generated R in nonpolar solvents, while the substitution product R-N was generated in polar solvents. Exploiting this unique solvent selectivity, a one-pot synthesis of polymer-N was attained. N 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-N in one pot. This one-pot synthesis was further applied to obtain N-chain-end-functionalized polymer brushes on the surface, uniquely controlling the N coverage (number density). Using the chain-end N, 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 NaN. In addition to N, thiocyanate (SCN) and cyanate (OCN) anions were also studied.

Polymer Dispersity Control by Organocatalyzed Living Radical Polymerization

“…Several approaches have been developed to manipulate values.Blending polymers with different molecular weights is often applied. [25][26][27][28] In RCMP,i odide anion (I À ; catalyst) coordinates R À I( dormant species) to form an R À I···I À complex through halogen bonding,a nd is followed by the R À Ibond cleavage to generate apropagating radical, RC. By optimizing the polymerization conditions such as catalyst loadings, initiators,temperatures,and additional chain-transfer agents, the was modulated at 1.1-2.0 in LRP.…”

“…[25][26][27][28] In RCMP,i odide anion (I À ; catalyst) coordinates R À I( dormant species) to form an R À I···I À complex through halogen bonding,a nd is followed by the R À Ibond cleavage to generate apropagating radical, RC. [25][26][27][28] In RCMP,i odide anion (I À ; catalyst) coordinates R À I( dormant species) to form an R À I···I À complex through halogen bonding,a nd is followed by the R À Ibond cleavage to generate apropagating radical, RC.…”

Metal‐Free Fast Azidation by Using Tetrabutylammonium Azide: Effective Synthesis of Alkyl Azides and Well‐Defined Azido‐End Polymethacrylates

“…In a second Schlenk flask, a solution of PMDETA (30.1 mg, 173 mmol) and PEG‐alkyne (90.0 mg, 0.087 mmol) in THF (1.0 mL) was purged with argon for 2 min. (The syntheses of PEG‐alkyne are described in a previous publication …”

Chain End‐Functionalized Polymer Brushes with Switchable Fluorescence Response

“…These include converting alkyl bromide end groups into amines before reacting with isothiocyanate‐functionalized dye as well as nitroxide radical exchange during polymerization . A straightforward alternative to these synthetic routes could be “click chemistry,” which was previously used to modify chain‐ends of polymer brushes with, for example, recognition elements, DNA, and polyethylene glycol (PEG) …”