Transition Metal-Catalyzed Living Radical Polymerization: Toward Perfection in Catalysis and Precision Polymer Synthesis

Abstract

Introduction 4964 2. Design of the Initiating Systems 4965 2.1. Required Initiating Systems 4965 2.1.1. Synthesis of Controlled Polymers Free from Catalyst Residues 4966 2.1.2. Environmentally Friendly and Inexpensive Catalysts 4966 2.1.3. Suppression of Side Reactions for High Molecular Weight Polymers and Perfect Block Copolymerization 4966

Metal-Free Atom Transfer Radical Polymerization

“…Analysis by ESI-MS again showed the expected oligomer distribution and chain ends with a very similar peak distribution and profile (Figure 3b). 1 H NMR was used to further confirm the level of incorporation and fidelity of the chain ends with resonances for the initiating ethyl 2-phenylacetate group being observed at ∼4.0 and 7.2 ppm. Integration of these resonances and comparison with resonances for the backbone allowed molecular weights to be calculated that were in full agreement with values obtained by both MS and GPC analysis (Figure 3c).…”

Recent developments in metal-catalyzed living radical polymerization

“…[83][84][85][86] PRECISION SYNTHESIS OF WELL-DEFINED POLYMERS Such significant developments in various living radical polymerizations have dramatically widened the scope of the accessible well-defined polymers with various architectures in comparison to living ionic and coordination polymerizations due to the robustness of the growing radical species to polar functional groups and the applicability for a wide variety of vinyl monomers. [6][7][8][9][10][11][12][13][14][15][16][17] Among the various metal catalysts for living radical polymerizations, ruthenium complexes show a relatively high tolerance to polar functional groups due to the lower oxophilicity of the ruthenium center and their non-ionic character.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] Besides these metal catalytic systems, there have also been substantial developments in various living radical polymerizations, such as nitroxide-mediated polymerizations, reversible addition fragmentation chain-transfer polymerizations and others, and in all of these, there are characteristic features of the mechanisms and components. [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] The metal-catalyzed living radical polymerization was originally discovered via evolution of the metal-catalyzed Kharasch or atom transfer radical addition reaction 35 to the chain-growth polymerization of vinyl monomers ( Figure 1).…”

“…Thus, a wide variety of conjugated monomers, such as methacrylates, acrylates, styrenes (Sts), acrylamides and acrylonitrile, can now be polymerized in a controlled fashion, although a truly well-controlled radical polymerization of unconjugated monomers such as vinyl acetate (VAc) is still one of the most challenging topics in metal-catalyzed living radical polymerizations. [6][7][8][9][10][11][12][13][14][15][16][17] In addition, the amounts of the metal catalyst used in the polymerizations have decreased owing to the evolution of the active catalysts or the addition of reducing agents for the oxidized metal catalysts. However, these are still challenges for industrial applications.…”

“…[6][7][8][9][10][11][12][13][14][15][16][17] They include not only well-known controlled polymer structures such as end-functionalized, block, graft and star polymers, but also other more complicated or unique structures, which have been extremely difficult to synthesize, such as gradient polymers, ring polymers and multiple controlled structures. In particular, for the precision synthesis of these highly ordered structures, metal-catalyzed systems are the most preferable methods in comparison to other living radical polymerization systems for the following reasons.…”