Butadiene-propylene

This technique has been applied to a study of sequencing in butadiene-propylene copolymer [80-82]. Samples of highly alternating copolymers of butadiene and propylene yielded large amounts of 3-methyl 1,6 hexane dial when submitted to ozonolysis. The ozonolysis product from 4-methyl cyclohexane-1 was used as a model compound for this structure. Ozonolysis of these polymers occurs as shown next  

The amount of alternation in these polymers can be determined if the amounts of 1,4- and 1,2-polybutadiene structure and total propylene have been determined by IR or NMR spectroscopy. Table 7.6 shows results obtained for several butadiene-propylene copolymers having more or less alternating structure. Similar polymers have been analysed by Kawasaki [67] by use of conventional ozonolysis methods with esters as the final products. 

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Very active catalysts for the preparation of strictly alternating butadiene-propylene copolymers (BPR) consist of V0(0R)2C1/i-Bu Al (R = neopentyl). The CH3 side groups in BPR stiffen the polymer chain and were expected to promote the formation of strain-induced structures. The fact that we could not detect strain-induced crystallization is probably due to an atactic configuration of the propylene units. 

The molecular weight of copolymers is controlled by means of the polymerization temperature. As Table VIII shows, butadiene-propylene copolymers with low Mooney viscosity are obtained at temperatures above -40 °C. A decrease of the reaction temperature increases the molecular weight. 

Table VI. Effect of R m VO(OR)2Cl on catalyst activity. Polymerization conditions moiar ratio butadiene, propylene is 1.1, monomer concentration, 31 wt. % in -hexane reaction, — 50°C catalyst, 0.8 mmol VO(OR)2Cl phm, 6.0 mmol i-Bu3Al phm reaction time, 3 h. Data from Ref. 19.

Table VIII. Effect of reaction temperature on molecular weight of butadiene-propylene rubber (BPR). Polymerization conditions as in Table VII, with i-Bu3Al as alkylaluminum compound. Data from Ref. 19.

Butadiene, propylene, and methane are major products as well as initial products in the decomposition of both 1- and 2-butene. Ethylene is not an initial product for 2-butene but does become a major product at high conversion levels. For 1-butene, ethylene becomes the most prominent product at high conversions. Hydrogen yield behavior is also different for the butene isomers. It is an initial product only in decomposition of 2-butene and its yield is largely independent of conversion level. For 1-butene decomposition, the hydrogen yield becomes significant only at high conversions. 

The addition of free radical initiators can produce different effects in the polymerization of CT complexes. Dibenzoyl peroxide increases the molar mass of the alternating copolymer from butadiene/propylene/VCL/EtsAl since hydrogen transfer is reduced. But addition of dibenzoyl peroxide to... 

T-2-Butene 1-Butene 1-Butene Propylene Propylene Ethylene Butadiene Propylene... 

The predominance of alternating structures was established by ozonolysis and by NMR techniques. In the case of the butadiene-propylene copolymers the butadiene units appear to be predominantly of the trorts-1,4 type. 

In view of the low cost of the monomers employed, the alternating butadiene-propylene rubbers may have more than academic interest. 

Table 5.14 shows results obtained for several butadiene-propylene copolymers having more or less alternating structure. 

Rank item p-Xylene Ethylene oxide Ethylene glycol Ammonium sulfate Cumene Acetic acid Phenol Butadiene Propylene oxide Carbon black Acrylonitrile Vinyl acetate Aluminum sulfate Cyclohexane Titanium dioxide Acetone... 

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