Olefins catalyzed polymerization

Figure 35 A noncoordinating carbosilane dendrimeric polyanion terminated with BR3 groups (52) used as a cocatalyst in the metallocene-catalyzed olefin polymerization. (Adapted from ref. 80.)...

Figure 36 Organoboron polymers of PS with well-defined boron-containing Lewis acids for use as a cocatalyst in metallocene-catalyzed olefin polymerizations. (Adapted from ref. 81.)... 

In the early stages of the metallocene-catalyzed olefin polymerizations the focus of research lay on C2- and CY-symmetric complexes [3, 12, 13], Since the beginning of the 1990s C,-symmetric catalysts have had more and more impact. The reason is... 

Chen EY, Marks TJ (2000) Cocatalysts for metal-catalyzed olefin polymerization activators, activation process, and structure-activity relationships. Chem Rev 100 1391-1434... 

Keywords Catalyzed olefin polymerization, Chain shuttling catalysis, Chain transfer, Olefin block copolymers, Thermoplastic elastomers... 

We note that there are NMR-based kinetic studies on zirconocene-catalyzed pro-pene polymerization [32], Rh-catalyzed asymmetric hydrogenation of olefins [33], titanocene-catalyzed hydroboration of alkenes and alkynes [34], Pd-catalyzed olefin polymerizations [35], ethylene and CO copolymerization [36] and phosphine dissociation from a Ru-carbene metathesis catalyst [37], just to mention a few. 

Under the reaction conditions employed, the oligomerization is living the aluminium is removed from the chain in a separate process step [2]. Further research on the Aufbau reaction led to the discovery of transition metal catalyzed olefin polymerization (Ziegler-Natta catalysis) [3]. 

The reaction mechanism of catalyzed olefin polymerization looks deceptively simple [31], and is shown in Fig. 1. The catalyst originally has an alkyl ligand and a vacant site. The olefin first coordinates by rj2 to the vacant site,... 

Early mechanistic studies concerning organolanthanide-catalyzed olefin polymerization reactions showed that insertion of the unsaturated hydrocarbon into the lanthanide-carbon cr-bond is a key step. It was first demonstrated for the... 

Solid-Catalyzed Olefin Polymerization. A third area where extremely challenging polymerization reaction engineering problems arise is in transition-metal catalyzed polymerization of olefins such as ethylene, propylene and their copolymers. 

However, much remains to be done, both experimentally and theoretically, before there will be a comprehensive understanding of transition-metal catalyzed olefin polymerization. 

Tempel DJ, Johnson LK, Huff RL, White PS, Brookhart M, Mechanistic Studies of Pd(II)-Diimine-Catalyzed Olefin Polymerizations, J Am Chem Soc, 122, 6686-6700 (2000)... 

Deng L, Woo TK, Cavallo L, Margl PM, Ziegler T, The Role of Bulky Substituents in Brookhart-Type Ni(II) Diimine Catalyzed Olefin Polymerization A Combined Density Functional Theory and Molecular Mechanics Study, J Am Chem Soc, 119, 6177-6186 (1997)... 

Michalak A, Ziegler T, DFT studies on substituent effects in Pd-catalyzed olefin polymerization, Organometallics, 19, 1850-1858 (2000)... 

Since mixing and good heat transfer are of vital importance in viscous polymerization reactions, a mechanically agitated continuous stirred-tank reactor is widely used in polymerization processes. Solution polymerization, emulsion polymerization, and solid-catalyzed olefin polymerization are all carried out in a mechanically agitated slurry reactor. 

Emulsion polymerization is usually carried out isothermally in batch or continuous stirred-tank reactors. Temperature control is much easier than for bulk or solution polymerization because the small ( 0.5 fim) polymer particles, which are the locus of the reaction, are suspended in a continuous aqueous medium. This complex, multiphase reactor also shows multiple steady states under isothermal conditions. In industrial practice, such a reactor often shows sustained oscillations. Solid-catalyzed olefin polymerization in a slurry batch reactor is a classic example of a slurry reactor where the solid particles change size and characteristics with time during the reaction process. 

Discussion Point DP3 Organic derivatives of the group 13 elements aluminium and boron are needed as essential components for almost all of the insertion-catalyzed olefin polymerizations. List four such compounds of interest and describe for each of them the structural and reactivity properties relevant to its action as activator jcocatalyst. Outline some of the features of polymerization catalysts that do not require any Al- or B-containing cocatalysts. 

In zirconocene-catalyzed olefin polymerizations similar processes are involved. Here polymerization rates depend at least linearly on olefin concentrations an... 

Figure 5.19. Proposed mechanisms for transition metal-catalyzed olefin polymerization.

For studies on palladium-catalyzed olefin polymerization, see (a) D. G. Musaev,... 

Gladysz, J. A., Ed. Chem. Rev. 2000, 100, (Themathic issue on metal-catalyzed olefin polymerization). 

The modeling of heterogeneous polymerization systems is generally more complicated than that of the homogenous systems because mass and heat transfer effects between two or more immiscible phases must be considered. Industrially important heterogeneous polymerization reactions include emulsion polymerization, suspension polymerization, precipitation polymerization, and solid-catalyzed olefin polymerization. The general polymerization rate equation is represented simply as... 

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