Reversible Generation of a Carbon-Centered Radical from Alkyl Iodide Using Organic Salts and Their Application as Organic Catalysts in Living Radical Polymerization

Abstract

A new method of producing carbon-centered radicals was discovered through the reaction of an alkyl iodide (R-I) with organic salts to reversibly generate the corresponding alkyl radical (R(•)). Via this new reaction, the organic salts were used as new and highly efficient organic catalysts in living radical polymerization. The catalysts included common and inexpensive compounds such as tetrabutylammonium iodide and methyltributylphosphonium iodide. Notably, the catalysts were highly reactive. They enabled the synthesis of high-molecular-weight polymers (up to Mn = 140,000) and the control of acrylate polymerization, which had been difficult with other organic catalysts. The organic salt catalysts were highly versatile, reacting with methacrylate, acrylate, styrene, acrylonitrile, and functional methacrylate monomers. Well-defined block copolymers were also prepared by using this method. A kinetic study quantitatively confirmed the high reactivity of these catalysts. Attractive features of this system include its low cost, its ease of operation, and its ability to access a wide range of polymer designs.

Macromolecular Architectures Designed by Living Radical Polymerization with Organic Catalysts

“…RTCP and RCMP can be facile and pervasive methodologies for various applications. We previously reported the use of RTCP and RCMP in preparing well-defined linear polymers including homopolymers, random copolymers, and diblock copolymers [16][17][18][19][20][21][22][23][24][25][26][27]. In this paper, we report new examples of diblock copolymers and summarize the diblock copolymers prepared in previous and current works.…”

“…Woolam, Lincoln, NE, USA) equipped with D 2 and QTH lamps with a polarizer angle of 45 degrees and an incident angle of 70 degrees. Table 1 summarizes examples of diblock copolymerization, including previously reported [18,27] and new results as indicated. Table 1 (entries 1-3) shows the block copolymerizations of MMA and GMA.…”

“…This I 2 /azo method was originally invented by Lacroix-Desmazes et al for iodide-mediated LRP [29,30]. This method was also effective for RTCP [17,18] and RCMP [25,27]. A low-polydispersity diblock copolymer (PDI = 1.39) was obtained (entry 3).…”

“…We developed two mechanistically different systems referred to as reversible chain transfer catalyzed polymerization (RTCP) [16][17][18][19][20][21][22][23] and reversible coordination mediated polymerization (RCMP) [24][25][26][27].…”

“…RCMP consists of a dormant species and a catalyst (activator). The catalysts include amines and organic salts such as tetrabutylammonium iodide (BNI) (Figure 1) [27] and methyltributylphosphonium iodide (BMPI) (Figure 1) [27] used in the present work.…”