Polymerization Living polymerizations Methyl

Group-Transfer Polymerization. Living polymerization of acrylic monomers has been carried out using ketene silyl acetals as initiators. This chemistry can be used to make random, block, or graft copolymers of polar monomers. The following scheme demonstrates the synthesis of a methyl methacrylate—lauryl methacrylate (MMA—LMA) AB block copolymer (38). LMA is CH2=C(CH2)COO(CH2) CH2. 

Otsu indeed observed some features of living/controlled radical polymerization when polymerizing methyl methacrylate (MMA) with the special azo-initiator 5 (Scheme 4.4). Thus, number average degree of polymerization DPji increased linearly with monomer conversion, and the molecular weight of the polymer increased when it was heated at 80 °C in the presence of fresh monomer. 

The diimine palladium compounds are less active than their nickel analogs, producing highly branched (e.g., 100 branches per 1,000 carbons) PE. However, they may be used for the copolymerization of Q-olefins with polar co-monomers such as methyl acrylate.318,319 Cationic derivatives, such as (121), have been reported to initiate the living polymerization of ethylene at 5°C and 100-400 psi.320 The catalyst is long-lived under these conditions and monodisperse PE (Mw/Mn= 1.05-1.08) may be prepared with a linear increase in Mn vs. time. 

The highly syndiospecific-living polymerization of methyl methacrylate has been initiated by the neutral bis(pentamethylcyclopentadienyl)lanthanide-alkyl or -hydride complexes [215,216]. The plausible reaction mechanism is shown in Scheme XI. 

Various block copolymers have been synthesized by cationic living polymerization [Kennedy and Ivan, 1992 Kennedy, 1999 Kennedy and Marechal, 1982 Puskas et al., 2001 Sawamoto, 1991, 1996]. AB and ABA block copolymers, where A and B are different vinyl ethers, have been synthesized using HI with either I2 or Znl2. Sequencing is not a problem unless one of the vinyl ethers has a substituent that makes its reactivity quite different. Styrene-methyl vinyl ether block copolymer synthesis requires a specific sequencing and manipulation of the reaction conditions because styrene is less reactive than methyl vinyl ether (MVE) [Ohmura et al., 1994]. Both monomers are polymerized by HCl/SnCLj in the presence of (n-CrikjtiNCI in methylene chloride, but different temperatures are needed. The... 

Scheme 7 A proposed mechanism for a living polymerization involving rapid methyl group transfer.

One-Shot" Lewis Acid Promoted Living Polymerization of Methyl Methacrylate [31]... 

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. 

Fig. 19. The polymerization flask designed for the synthesis of high-molecular-weighi (Mn>500,000) poly(methyl methacrylates) by the high-speed living polymerization with the (porphyrinato)aluminium enolate (2)-Lewis acid (3e) systems...

Amorphous isotactic TPX was synthesized from 4-methyl-l-pentene in the presence of the zirconium complex as the catalyst of living polymerization. The catalyst is shown in Figure 4.4. 

D. Kisun ko, D. Lemenovskii, and A. Aladyshev, Synthesis of isotactic copolymers of 4-methyl-l-penteneby living polymerization catalyzed by zirconium non-metallocene complexes, Polym. Sci. Ser. A, 48(12) 1227-1231, 2006. 

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