Living Radical Polymerization of Methyl Methacrylate with a Rhodium(III) Complex–Organic Halide System in Dimethyl Sulfoxide

Abstract

ABSTRACT:The polymerization of methyl methacrylate (MMA) with the rhodium(III) complex dihydrido(1,3-diphenyltriazenido)bis(triphenylphosphine)rhodium(III) [RhH 2 (Ph 2 N 3 )(PPh 3 ) 2 ] as a catalyst and an organic halide (CCl 4 , BrCCl 3 , or CBr 4 ) as an initiator in dimethyl sulfoxide (DMSO) was studied. For the CCl 4 initiator system, a kinetic study of MMA polymerization indicated that polymerization follows first-order kinetics with respect to the monomer and that the number-average molecular weight (M n ) of the polymers produced increases in direct proportion to the monomer conversion. Monomer-addition experiments showed that after addition of further MMA, the M n of the polymers continues to increase in direct proportion to the monomer conversion. These results confirmed that the polymerization of MMA in the CCl 4 -initiated system proceeds in a living radical manner. In contrast, the systems involving the bromo compounds BrCCl 3 or CBr 4 did not show such a living radical nature. For all these initiator systems, the polymers produced had broad molecular-weight distributions. The catalytic activities are discussed in relation to the reaction product between RhH 2 (Ph 2 N 3 )(PPh 3 ) 2 and DMSO. Free-radical polymerization is one of the most widely used techniques for producing polymers. However, in conventional radical-polymerization processes, it is rarely possible to control the molecular weight or the molecular-weight distribution of the product. Recently, the chemistry of such less-easily controlled reactions has been changed by progress in transition metal-mediated living or controlled radical polymerization systems that permit the control of molecular weights and their distribution. Such catalyst systems were first reported independently by Sawamoto and his co-workers 1 and Wang and Matyjaszewsky 2 in 1995. Sawamoto and his co-workers reported that methyl methacrylate (MMA) is polymerized homogeneously in toluene in the presence of a carbon tetrachloride-ruthenium complex system, (CCl 4 )/ RuCl 2 (PPh 3 ) 3 , and a Lewis acid activator (methylaluminum bis(2,6-di-tert-butylphenoxide).1 Wang and Matyjaszewsky reported the bulk polymerization of styrene in the presence of a system consisting of 1-phenylethyl chloride/CuCl and 2,2 0 -bipyridyl. 2 Since then, systems based on other low-valent transitionmetal complexes of iron(II), [3][4][5][6][7][8][9][10][11][12][13][14][15][16] nickel(II), 17-21 rhodium(I), [22][23][24] and palladium(II) 25 have been found to be effective in similar living or controlled radical polymerizations. The transition-metal complex plays an indispensable role as a halogen carrier, through a series of consecutive reversible oxidation and reduction reactions involving single-electron transfers.In a previous paper, 26 the trivalent rhodium complex dihydrido(1,3-diphenyltriazenido)bis(triphenylphosphine)rhodium(III) [RhH 2 (Ph 2 N 3 )(PPh 3 ) 2 ] in conjunction with CCl 4 was shown to be effective as an initiator system for the polymerization of MMA. Under the conditions used p...

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

“…Some complexes with rhodium (Rh), palladium (Pd), and rhenium (Re) had been reported for living radical polymerization before the last review article, but since then, there were few reports on the evolution of these complexes. Just a rhodium complex [RhH 2 (Ph 2 N 3 )(PPh 3 ) 2 ] for styrene-polymerization was reported, with a poor performance ( M w / M n > 2) . Rh(I) and Pd(0) are well-known to catalyze organic reactions, and usually the catalytic cycle involves an oxidative addition and a reductive elimination with two electrons transfer.…”

“…Just a rhodium complex [RhH 2 (Ph 2 N 3 )(PPh 3 ) 2 ] for styrenepolymerization was reported, with a poor performance (M w / M n > 2). 164 Rh(I) and Pd(0) are well-known to catalyze organic reactions, and usually the catalytic cycle involves an oxidative addition and a reductive elimination with two electrons transfer. For this reason, these complexes might be less suitable for metal-catalyzed living radical polymerization via one electron transfer.…”

Fluoropolymer: A Review on Its Emulsion Preparation and Wettability to Solid-Liquid Interface

“…Moreover, the elimination of small molecule polycondensation is more accurate in fluoropolymer emulsion ( Figure 1 d). Unlike addition polymerization, polycondensation mainly relies on the elimination of the end groups in monomers [ 52 ]. Generally, a monomer has two or more easily eliminated functional groups, such as hydroxyl, amino, halogen atoms, etc.…”

Controlled/“Living” Radical Polymerization of Methyl Methacrylate Catalyzed by Cobalt Acetate

“…[1,[9][10][11][12] Traditionally, ATRP is based on the catalysis of transition-metal halide/ ligand complexes, which is the key point in ATRP. Up to now, various catalytic systems based on copper, [7] iron, [13] nickel, [14,15] cobalt, [16][17][18] ruthenium, [6,19,20] molybdenum, [21,22] rhenium, [23] rhodium [24] and osmium [25] have been employed in ATRP. However, it is still necessary to develop new ATRP catalytic systems, especially cheaper ones.…”