Triethylaluminium polymerization

Fink and Babik reported that propylene polymerization was achieved by a bis (imino)pyridine iron complex with Ph3C[B(C6p5)]4] and ttialkylaluminium as additives [127]. Both 3-methyl-"butyl and "butyl endgroups were observed by NMR spectrum when ttiisobutylaluminium as an activator was used, whereas the only "propyl endgroup was formed in case of triethylaluminium activation. In addition, this polymerization proceeds two times faster with than without a hydrogen atmosphere, but the value decreases and the M IM value rises up. 

As early as 1954, Karl Ziegler [301,302] has assumed that colloidal nickel in triethylaluminium is the crucial co-catalyst which effects the controlled polymerization... 

The accelaration of styrene photopolymerization by oxygen is also explained by excitation of the DA complex of these two substances [82], A copolymer is produced which decomposes upon illumination [83]. Polymerization of methyl methacrylate is initiated by the photoexcited complex of the monomer with triethylaluminium [84]. Methyl methacrylate, acrylonitrile and acrylates in general readily produce unstable DA complexes which decompose to products quite different from the initial components. Methyl methacrylate, for example, polymerizes in the presence of quinoline and bromine. With the monomer, these pairs yield a DA complex which is unstable upon illumination [85a]... 

An interesting synthesis of block copolymers by cationic polymerization of vinyl compounds was described by Kennedy and Melby [277] who used 2-chloro-6-bromo-2,6-dimethylheptane as coinitiator. Br- is eliminated by triethylaluminium, and styrene can be polymerized, without transfer, on the generated carbocation. After all the styrene has reacted, diethylaluminium chloride is added to eliminate Cl- from the coinitiator and thus produce new carbocations on the polymer chain. In the presence of 2-methylpropene, the two-block copolymer poly(styrene)-6/ock-poly(2-methylpropene) is formed. 

The coordinate type catalysts are also effective for thiirane polymerizations. The types of systems used are also similar. Thus diethylzinc and in particular diethylzinc/water mixtures have been studied [44]. Other studies made using triethylaluminium and diethylcadmium indicated that these metal alkyls all behave similarly. The reactions seem to be rather complex, and, as also was the case with the epoxides, no well defined kinetic studies have appeared. The polymers produced are of high molecular weight and are often crystalline. Thus stereospecific polysulphides have been reported. Again the bulk of the studies involve PS. Stereoselective polymerization of racemic monomer has been accomplished [45, 46] using a catalyst prepared from diethylzinc and (+) borneol. The marked difference between PO and PS in their polymer-... 

Other Solid-add Catalysts - Chromium on an aluminophosphate support, which is supposed to be a polymerization catalyst, was used in the oligomerization of light olefins and ethylene. For ethylene oligomerization, the catalyst exhibited activity for dimerization, with around 60% conversion to C4 fractions. In another patent the support and the active phase were the same as in the previous patent, except that the support had been treated with a solution of triethylaluminium in toluene before being contacted with the chromium compound. The catalyst system showed selectivity towards trimerization. When... 

In addition Ziegler-Natta polymerization reactions have also shown some success when carried out in ionic liquids. The most common production methods for this form of polymerization involve the use of triethylaluminium catalysts at ca. 100°C and 100 atmospheres pressure. Advances have been developed through the use of organometallic transition metal catalysts, typically nickel or titanium. Given the solvent characteristics of ionic liquids it should be possible to effectively immobilize such catalysts in an ionic liquid solvent. Indeed, Carlin and Wilkes have reported the Ziegler-Natta polymerization of ethene in an ionic liquid solvent. In these reactions an acidic [Cj-mimJCl-AlClj ionic liquid solvent was used to support dichlorobis(Ti -cyclopentadienyl)titanium(IV) with an alkyl-chloroaluminium(III) co-catalyst. 

By treatment of these materials with titanium tetrachloride valuable supported catalysts for the propene Ziegler-Natta type polymerization were obtained. These catalysts were tested by slurry polymerization using triethylaluminium as cocatalyst and showed an interesting activity compared with that exhibited by a commercial catalysts. The polymer products were also characterized by measuring the molecular weight distribution by gel permeation chromatography technique. 

As mentioned earlier, polymers of formaldehyde are described in the next section. Polymers of higher aliphatic aldehydes and ketones have been extensively investigated but, in general, they do not have the stability necessary for commercial development. For example, acetaldehyde may be polymerized using organometallic initiators at low temperatures, e.g., triethylaluminium at —78 C in this case crystalline isotactic polymer is obtained. Also, the polymerization of acetaldehyde may be effected with cationic initiators at low temperatures (e.g., aluminium chloride at —65°C) or with metal oxides at low temperatures (e.g., alumina at —70°C) in these cases amorphous atactic polymer is obtained. The tacticity of polyacetaldehyde arises because the polymer comprises structural units which contain an asymmetric carbon atom ... 

The ternary catalyst system, shown in Fig. 7, consists of Ba tert-butoxide [Ba(t-BuO)2] in combination with a complex of dibutyl-magnesium (Bu2Mg) and triethylaluminium (EtsAl) Ba/Mg/Al. It was found to be useful in controlUng stereoregularity of butadiene polymerizations and in providing SBRs with high tack and green... 

Although some deviation from linearity is evident at low triethylaluminium concentrations these plots indicate that there is good agreonent with the model. It should be noted that the values of alkyl concentration required in equation (10) are the equilibrium values and these will differ substantially from the values at the beginning of the polymerization for low alkyl concentrations. 

Figure 8. Plot of 1/R versus triethylaluminium concentration at various polymerization times for Cat-E at 60°C.

This decrease in polymerization rate is consistent with a model involving competitive adsorption of triethylaluminium. 

Figure 3. Gas phase polymerization with triethylaluminium and trihexylaluminiuB...

Preparation of HDPE in heptane slurry polymerization results in differences in activity, MH and MWD when different trialkylaluminia are used. The more reactive triethylaluminium (TEA) is able to form the active centers in a rather short time but also to deactivate them. The kinetic curve is of type 3 (fig. l). 

At the same time an Italian scholar G. Natta received for the first time the isotactic polypropylene by polymerization of propylene on the catalyst complex composed of titanium trichloride and triethylaluminium. 

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