Polymerization high-speed living

Fig, 4, Schematic illustration of high-speed living polymerization of methacrylate esters accelerated by steric separation of the aluminum porphyrin nucleophile and bulky Lewis acid. ... 

Fig. 11. The basic concept of the Lewis acid assisted high-speed living anionic polymerization of methacrylic esters...

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...

The key point of the high-speed living polymerization is the steric suppression of an undesired reaction between the nucleophilic growing species and the Lewis acid, for which not only the steric bulk of the Lewis acid but also that of the porphyrin ligand is considered important. The benefit of using a Lewis acid holds even for the aluminum complexes with phthalocyanine (11), tetraazaannulene (12), and. Schiff bases (13-15). As initiators, these complexes exhibit much lower activity for the polymerization of PO than aluminum porphyrin 1 (X=C1). 

The MAD-(TPP)A1X system was extended to the polymerization of methacryloni-trile (Scheme 6.178). The high-speed living nature of this procedure was preserved to give atactic (mm mr rr=28 52 20) polymers [230]. 

An example of the Lewis acid assisted high-speed living anionic polymerization is given by the polymerization of methyl methacrylate (21, R = Me) initiated with (TPP)AlMe (la) [(MMA)o/(la)o = 217] in CH2CI2. The polymerization at 35°C under irradiation with visible light (>420nm) proceeds to attain only 6.1% monomer conversion in 2.5 hours. On the other hand, upon addition of a... 

Table 6. Lewis Acids for High-Speed Living Anionic Polymerization...

Lewis acid-assisted high-speed living anionic polymerization can be applied not only to the accelerated synthesis of naiTOw MWD poly(methacrylic esters) but also to the synthesis of polyethers from epoxides (11) and polyesters from lactones (14 and 15) with aluminum porphyrins as initiators. Furthermore, ring-opening polymerization of episulfides (18) with zinc AT-substituted porphyrins (5) can also be accelerated by Lewis acids. 

Goto A, Kwak Y, Fukuda T et al (2003) Mechanism-based invention of high-speed living radical polymerization using organotellurium compounds and azo-initiators. J Am Chem Soc 125 8720-8721... 

Adachi, T. Sugimoto, H. Aida, T. Inoue, S. Aluminum thiolate complexes of porphyrin as excellent initiators for Lewis acid-assisted high-speed living polymerization of methyl methacrylate. Macromolecules 1993, 26,1238-1243. 

Figure 11 Schematic representation of the concept of high-speed living polymerization by aluminum porphyrin as a nucleophile. Reprinted from Sugimoto, H. Kawamura, C. Kuroki, M. etal. Macromolecules 9SA, 27,2013. with permission of the American Chemical Society, USA.

The living/controlled and high-speed nature of the ring-opening polymerization of POx with aluminum por-phyrin/a bulky organoaluminum compound was further demonstrated by the successful synthesis of block copolymers from POx and BOx. " ... 

Microtubules are used to cover relatively long distances in the cell. Therefore, the short distance between the cell surface and the early endosomes does not require microtubules (94,136). They are involved in the later steps in endocytosis early endosomes accumulate endocytic material for about 10 minutes and then generate transport vesicles (0.5 pm in diameter), which will be taken to the cell center with a relatively high traveling speed of Ipm/sec (with velocities of up to 2.5pm/sec) (95,137). These transport vesicle move on microtubule-tracks to the cell center (and to the ly sosome) (94). When performing live cell imaging studies, it should be kept in mind that microtubules are extremely sensitive to ultraviolet light, which causes their polymerization. 

The period following the Second World War saw the emergenee, with an accelerated speed, of new polymerization methods in 1953-1954, polymerization catalysis by coordination was developed by K. Ziegler and G. Natta (Nobel Prize, 1963), which led to for high-density polyethylene (PEHD) and polypropylene (PP). Anionic polymerization and the concept of living polymerization proposed by M. Szwarc in 1956 led to the design of blocks copolymers and the first macromolecular architectures. We then saw the emergence of catalysis by metallocene in 1980 by W. Kaminski. Radical polymerization controlled by M. Sawamoto and K. Matyjaszewski in 1994 combined the benefits of radical and ionic polymerization without the drawbacks of the former. 

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