Polymerization Vandenberg catalyst

Mechanism of polymerization. The AlEt3/H20/acetylacetone catalyst called also chelate Vandenberg catalyst is a stable and soluble product having the structure presented in Fig. 17. 

Because of the aliphatic chlorine atom, base-catalyzed initiation of epichlorohydrin to relatively high polymer is not practical. Coordinate polymerization is used with the Vandenberg Catalyst, as will be discussed in Section III. Polyepichlorohydrin is used commercially as an oil-resistant rubber. 

Some of the complexities of coordination copolymerization of alkylene oxides are highlighted by the work of Vandenberg with 2,3-epoxybutanes (88). Using the Vandenberg Catalyst, it was shown that one could selectively polymerize cis-2,3-epoxybutane from an equal mixture of cis- and trans-isomers and obtain fairly pure cis-polymer. The cis-oxide enters the crystalline polymer fraction about 20 times faster than does the trans-oxide. In the amorphous fraction of the polymer produced, the enrichment of cis-oxide was about tenfold over that of the trans-isomer. 

Vandenberg (77) has found that vinylethers are polymerized by combinations of vanadium tetrachloride and triethylaluminum. Vandenberg believed that the intermediate vanadium trichloride, produced by reduction of the vanadium tetrachloride, reacted with the triisobutyl-aluminum-tetrahydrofuran complex to produce the modified Friedel-Crafts catalysts that converted the vinylether to isotactic polymer. 

From patent literature, it appears that Vandenberg (353) was the first to polymerize vinyl ethers to crystalline polymers using modified Ziegler catalyst preparations. A series of papers have been published by Vandenberg and his associates which describe the polymerization of simple alkyl vinyl ethers (29), ROCH=CHCHs (354), CH30CH=CH--CH=CH2 (355), and epoxides (356). 

Recently Vandenberg (189) published additional information on vinyl ether polymerizations with Ziegler type catalysts. Details of the catalyst preparations, polymerization conditions and polymer characterization were presented together with an excellent discussion of mechanism. 

An important step seems to be the coordination of the monomer on the metal catalyst site. Vandenberg [34] concludes that two or more aluminium atoms must be involved in the polymerization. The props a-tion step is then supposed to involve some charge separation and the development of a partial or full positive charge on the monomer while the counter anion is located on the catalyst complex. 

Kioka, M. Mizuno, A. Tsutsui, T. Kashiwa, N. 1-Butene Polymerization with Ethylenebis-(l-Indenyl)Zirconium Dichloride and Methylaluminoxane Catalyst System. In Catalysis in Polymer Synthesis, ACS Symposium Series Vandenberg, E. J., Salamone, J. C., Eds. American Chemical Society Washington, DC, 1992 Vol. 496, p 72. 

In I960 Vandenberg observed for the first time the positive influence of water on the activity of organoaluminum catalysts in the polymerization of organic monomers. As this activity achieved its maximum for A1 to H2O molar ratios of 1 1 or 2 1 he postulated aluminoxanes (RAlO)n or dialuminoxanes (R2A10AlR2)n as the active catalytic species. Since that time, many people have worked in this field trying to prepare aluminoxanes and/or dialuminoxanes, to explore their properties and most of all to determine the structures of these compounds. 

In work investigating the mechanism of this system, Vandenberg used AIR3/H2O catalysts to polymerize cis- and tra i-2,3-epoxybutane. From the properties of the resultant polymers and the examination of the diol decomposition products, mechanistic information was obtained. These results are summarized in Scheme... 

The polymerization o oxetanes with cationic catalysts has been studied by many investigators. (1.H2) RoseC. ), in particular, first reported the homopolymerization of the parent compound, tri-methylene oxide (TMO), with a Lewis acid catalyst, boron trifluoride. The use of coordination catalysts to polymerize oxetanes has been reported in the patent literature by Vandenberg.W In this work, Vandenberg polymerized oxetanes with the aluminum trialkyl -water-acetylacetone coordination catalyst (referred to as chelate catalyst) that he discovered for epoxide polymerization . This paper describes the homo- and co-polymerization of TMO with these coordination catalysts. Specific TMO copolymers, particularly with unsaturated epoxides such as allyl glycidyl ether (AGE), are shown to provide the basis for a new family o polyether elastomers. These new elastomers are compared with the related propylene oxide-allyl glycidyl ether (PO-AGE) copolymer elastomers. The historical development and general characteristics of polyether elastomers and, in particular, the propylene oxide elastomers, are reviewed below. 

This TOO polymerization with the chelate catalyst no doubt involves coordinate propagation and is the first such case of coordinate propagation of an oxetane. Heretofore, oxetanes have been cationically polymerized. There are several reasons for concluding that this chelate catalyst system is a coordination polymerization. First, the very high molecular weight obtained at elevated temperature with a low rate is characteristic of coordination polymerization rather than of cationic polymerization. Also, Vandenberg s work on the cis- and trans-2,3-epoxy-... 

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