Ethylene/styrene copolymerization using

While most conventional catalysts failed to copolymerize st)n ene, halfsandwich-metallocene catalysts proved very effective in styrene copolymerization. In addition to random copolymers, specific catalysts were found to produce alternating copolymers. Semetz et al. [15] determined copolymerization parameters of random ethylene/styrene copolymerization using single site (CpMe4)SiMe2N(tert.Bu)TiCl2/MAO to be... 

ETHYLENE/STYRENE COPOLYMERIZATION USING TRANSITION METAL COMPLEX-COCATALYST SYSTEMS... 

TABLE 5.2 Ethylene/Styrene Copolymerization Using Ifae Cp Ti(Cll2Pli)3-B(C F5)r-ArBn3 Catalyst Sy tem[12b] ... 

TABLE 5.10 Ethylene/Styrene Copolymerization Using Dichloro l,4-dithiabntanediyl-2,2 -bis(4,6-di-tert-bntylphenoxy) Titaninm Complex (20)-MAO Catalyst System[46] ... 

Although ordinary metallocenes are inactive for styrene polymerization, certain metallocenes can be effective for ethylene/styrene copolymerization [20-23]. Oliva et al. reported that the regiospecificity of styrene insertion into the Zr- CHs bonds is predominantly secondary in ethylene/styrene copolymerization using the [Me(Ph)C(fluorenyl)(Cp)]ZrCl2-MAO catalyst system [20]. Oliva later presented that some styrene units can be introduced in an isotactic polypropylene sequence (1,2-insertion) by using a small amount of ethylene to reactivate the catalyst after the styrene insertion (2,1-insertion) in propylene/styrene copolymerization using a r c-[Et(indenyl)2]ZrCl2-MAO catalyst system [21]. 

TABLE 5.11 Ethylene/Styrene Copolymerization Using a Series of Metallocenes[22a] ... 

FIGURE 14.24 Structures of group 4 metal complexes used for ethylene-styrene copolymerizations. 

Uses. There are about forty to fifty organic peroxides commercially available in more than seventy formulations designed for specific applications which include (1) initiators for vinyl monomer polymerizations, and copolymerizations of monomers such as vinyl chloride, ethylene, styrene, vinyl acetate, acrylics, fluoroolefms and buta-dienestyrene (2) curing agents for thermoset polyesters, styrenated alkyds and oils, silicone rubbers and poly allyl diglycol carbonates ... 

Uses. The azobisnitriles have been used for bulk, solution, emulsion, and suspension polymerization of all of the common vinyl monomers, including ethylene, styrene vinyl chloride, vinyl acetate, acylonitrile, and methyl methacrylate. The polymerizations of unsaturated polyesters and copolymerizations of vinyl compounds also have been initiated by these compounds. 

More industrial polyethylene copolymers were modeled using the same method of ADMET polymerization followed by hydrogenation using catalyst residue. Copolymers of ethylene-styrene, ethylene-vinyl chloride, and ethylene-acrylate were prepared to examine the effect of incorporation of available vinyl monomer feed stocks into polyethylene [81]. Previously prepared ADMET model copolymers include ethylene-co-carbon monoxide, ethylene-co-carbon dioxide, and ethylene-co-vinyl alcohol [82,83]. In most cases,these copolymers are unattainable by traditional chain polymerization chemistry, but a recent report has revealed a highly active Ni catalyst that can successfully copolymerize ethylene with some functionalized monomers [84]. Although catalyst advances are proving more and more useful in novel polymer synthesis, poor structure control and reactivity ratio considerations are still problematic in chain polymerization chemistry. 

The fact that ethylene will copolymerize at high pressures is rather fortunate from not only a commercial but also a theoretical view, since it has long been believed that monomer reactivity ratios might be better correlated according to a scheme based on ethylene rather than the currently used Q-e correlation in which styrene is taken as the reference standard. However, until recently no quantitative data on ethylene copolymerizations have been available upon which to base such a scheme. 

The less nucleophilic acetals copolymerize with vinyl compounds more readily. Perhaps, in these systems the alkoxycarbenium ions (... —OCH ) that coexist in equilibrium with oxonium ions facilitate copolymerization with vinyl compounds. Styrene copolymerizes with trioxane 51,52) and tetraoxane53). The latter system yields polytrioxane and trioxane-styrene copolymer together with 1,4-phenyl-1,3-dioxane. It was formed in 25% yield in ethylene dichloride at 30 °C after 1 hr using [BF3 OEtj] = 10-2 mol l-1, [styrene], = [tetraoxane = 0.5 mol l-1. The proposed mechanism of 4-phenyl- 1,3-dioxane formation is shown below (cf. also Chap. 7) ... 

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