Determination of the dependence of the chain transfer constant on the degree of polymerization by analysis of molecular weight distributions

The 25th anniversary of catalytic chain transfer

“…For instance, polydispersity narrows when the length of the propagating radical decrease to 10 monomer units or less. Smirnov 14 first noticed that the PDI tends to decrease below the expected 2 for degrees of polymerization less than 20. At the same time, the efficiency of the catalysis decreases.…”

The Effects of Ester Chain Length and Temperature on the Catalytic Chain Transfer Polymerization of Methacrylates

“…[1][2][3][4][5] This technique is based upon the property of certain low-spin Co(II) complexes to catalyze the chain transfer to monomer reaction (shown in Scheme 1 for the polymerization of methyl methacrylate). [1][2][3][6][7][8][9][10] It has been well-established that virtually all chains are initiated by a hydrogen atom and terminated by a vinyl end group, [6][7][8] but despite many efforts, [6][7][8][9][10][11][12][13][14][15][16][17][18][19] most notably those by Gridnev and coworkers [20][21][22][23][24][25][26][27] a fully consistent and unambiguous mechanism has not yet appeared.…”

“…Catalytic chain transfer polymerization is a relatively recent technique for the production of vinyl end-functionalized low-molecular weight polymers via free-radical polymerization. − This technique is based upon the property of certain low-spin Co(II) complexes to catalyze the chain transfer to monomer reaction (shown in Scheme for the polymerization of methyl methacrylate). − ,− It has been well-established that virtually all chains are initiated by a hydrogen atom and terminated by a vinyl end group, − but despite many efforts, − most notably those by Gridnev and co-workers 20-27 a fully consistent and unambiguous mechanism has not yet appeared.

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Catalytic chain transfer and its derived macromonomers

“…The Co III H complex then reacts with a monomer molecule yielding back the original Co II catalyst and a monomeric radical, which can start growing. This mechanism has been studied in detail [1][2][3][4][5][6][7][8][9][10][11][12]20,21,[23][24][25][26][27][28]57,60,65,67,82 and can be summarized in the catalytic cycle of Scheme 3. 1,27 In polymerization kinetic terms, the CCT process is just a chain transfer process with fast re-initiation and to a first approximation does not affect the rate of polymerization in any other way than do ordinary chain transfer agents (with the obvious exception of catalytic inhibition).…”

“…1 Smirnov and Marchenko discovered that certain low-spin Co II complexes, in particular Co II porphyrins (1), efficiently catalyze the chain transfer reaction to monomer reaction. [2][3][4][5][6][7][8] Further studies and developments by the Russian group (most notably by Gridnev), [9][10][11][12] the Glidden Paint company, [13][14][15] DuPont, 16,17 ICI/ Zeneca 18,19 and Ken O'Driscoll 20,21 have led to considerable insight into the catalytic process and to the very active cobaloxime catalysts (2, 3) (Scheme 1).…”