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. 

Cyclohexene oxide Vandenberg Catalyst Crystalline fraction 76... 

Trans-monomer Vandenberg Catalyst 65 Small yield Crystalline, mp = 100°C, meso-diiso-tactic... 

With propylene oxide and aluminum-based initiators, such as the Vandenberg Catalyst, the mechanism proposed can be rep-... 

A bimetal initiator system was explored by Kuntz (104) involving an aluminum complex similar to the Vandenberg Catalyst and diethylzinc. The bimetal complex could be envisaged as... 

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. 

Vogl and coworkers (4) copolymerized omega-epoxyalkanoates with a range of alkylene oxides using the Vandenberg Catalyst and obtained comparable results. With a range of alkylene oxides and one coordination initiator, relative copolymerization rates indicated that random copolymers were formed (Table 12). The copolymerization of ethylene oxide and cyclohexene oxide with the Vandenberg Catalyst also proceeds with a relative copolymerization rate of about 1.0 (88). 

TABLE 12 Copolymerization of Alkylene Oxides with Omega-Epoxyalkanoates with AlEt3/H20/AcAc Initiator (Vandenberg Catalyst) (From Ref. 4.)... 

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