Living polymerization of MMA

The well-defined single-site magnesium enolate initiator (187) initiates the living polymerization of MMA at -30 °C.452 Mw/Mn values are typically 1.07-1.11, and Mn increases linearly both with... 

For Lewis acid promoted living polymerization of MMA with (TPP)AlMe (1,X= Me) as initiator, a photoinitiation prior to the addition of the Lewis acid is required. This is because (1) 1 (X=Me) without irradiation does not have the ability to initiate the polymerization even in the presence of Lewis acid, and (2) all-at-once polymerization by direct irradiation of a mixture of MMA, 1 (X=Me), and the Lewis acid results in the formation of a relatively broad MWD PMMA with Mn much higher than expected. In this sense, the procedure using 1 (X= Me) as initiator is not convenient for practical application. In this section, we report on aluminum porphyrins with various axial ligands which were tested as initiators in order to realize a more convenient, one-shot high-speed living polymerization of methyl methacrylate with no need for irradiation with visible light. 

Prepared by the living polymerization of MMA initiated with (TPP)AlMe (1) inCH2Cl2at 35 °Cunder irradiation with xenon arc light (X>420 nm) in the presence of methylaluminum bis(2,6-di-rert-butyl-4-methylphenolate) (3e), 100% conversion. 

The homopolymerization of MMA with the soluble catalyst was found to exhibit the characteristic of living polymerization at the initial stage of polymerization ( 5 h) giving poly(MMA) with a narrow molecular weight distribution (Mw/IVln = 1.2, Mn = 2400), at 25 °C. To elucidate the mechanism of the MMA polymerization, the copolymerization of MMA with styrene was carried out. The observed reactivity ratios (rs = 0.5, rMMA = 0.4) indicated that the living polymerization of MMA occurred via a radical intermediate. 

Yasuda [59, 60] has found that (Cp )2SmH (Cp =C5Me5) will initiate living polymerization of MMA. Very high molecular weight polymer with low MWDs is produced (Scheme 25a). A block polymer with ethylene has been made. Novak [61] claims that a dimer intermediate first forms (Scheme 25b). 

Another real active species was isolated form the reaction of [Cp 2SmH]2 with two equivalents of MMA monomer (methyl methacrylate) [289]. Or-ganolanthanide complexes of type Cp2LnR (R = H, alkyl) are not only effective precatalysts in the polymerization of nonpolar monomers such as ethylene, but also initiate the ideal living polymerization of MMA [289-291]. 

In addition, Sawamoto et al. [137, 140] detail the radical living polymerization of MMA with an initiating system that consists of CC14, RuCl2(PPh3)3 and methyl aluminium bis (2,6-ditertbutyl phenoxide) (MAO-type) with a constant polydispersity index vs conversion rate (Mw/Mn = 1.3). According to the authors, the polymerization is considered to proceed via repeating radical... 

Despite this slow initiation, MeOPEG-I is efficient enough to result in living polymerization of MMA, with good kinetics and excellent final product properties. 

Some of the most defining work carried out on the coordinative polymerization of MMA was reported in the early 1990s by Yasuda," -" who described the living polymerization of MMA by lanthanocene catalysts. The complex [Cp2Sm((r-H)]2 (Cp = CsMes) (1, Scheme 23.4) was shown to afford high molecular weight PMMA with very low polydispersities (Mw/Mn < 1.05). At —95 the polymer... 

Table 3 Isotactic living polymerization of MMA with t-butyl-MgBr in toluene at —78 °C [169]. 

Living polymerization in water also led to polymers with a relatively narrow molecular mass distribution (1.1-1.3) and molecular masses, which showed linear increase with conversion, indicating the living character of this polymerization [320]. Recently, Matyjaszewski et al. reported both reverse and direct ATRP of n-butyl methacrylate in an aqueous dispersed system via the miniemulsion approach, characterized by a linear increase of the molecular mass with conversion and a narrow distribution of molecular masses [321]. The suspension-type process of living polymerization of MMA in water not only led to well controlled and high molecular masses and low PDIs, but also the polymerization proceeded without the addition of Al(0-i-Pr)3 and clearly faster than ATRP in organic solvents [322]. 

RAFT agent, like dithionaphthalate, as the initiator, a simple ferrocene (Fe-32) induced a faster living polymerization of MMA than that by thermal initiation at 115 °C, though the contribution of the iron complex for the propagation was unclear. ... 

A further improvement was obtained by Hamada et al. at Kuraray company by adding multidentate o-ligands, like DME, to these systems, allowing for the living polymerization of MMA and even nBA at 0 At present this system... 

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