Butadiene with lithium morpholinide

Polymerization of butadiene with lithium morpholinide, an initiator with a built-in microstructure modifier, has been carried out in hexane. In general, the vinyl content of the polymers prepared with this initiator is dependent on the initiator concentrations and on the polymerization temperatures. This dependence is identical to that observed in a THF-modified lithium diethylamide polymerization initiator system. A comparison of these initiator systems for polymerization of butadiene is presented. In addition, a study of the effect of metal alkoxides on the vinyl content of lithium morpholinide initiated butadiene polymerization is included. 

The polymerization of butadiene with lithium morpholinide was carried out in hexane at several different temperatures. 

Lithium Diethylamide. This compound has been used as an initiator for the polymerization of diene by Vinogrador and Basayeva (1). In order to compare this initiator with lithium morpholinide (a lithium-nitrogen initiator with a built-in polar modifier), we have prepared lithium diethylamide according to the procedure described by vinogrador and Basayeva (1) and utilized it as an initiator for THF-modified butadiene polymerizations. 

The temperature dependency of 1,2 content shown in Table II is also consistent with complex formation between polybutadienyl-lithium and the oxygen atom in the lithium morpholinide moleculre. One can visualize an equilibrium between noncom-plexed and complexed molecules which would be influenced by temperature. Higher temperatures would favor dissociation of the complex and, therefore, the 1,2 content of the polymer would be lower than that from the low temperature polymerization. This explanation is supported by the polymerization of butadiene with lithium diethylamide, in which the microstructure of the polybutadiene remains constant regardless of the polymerization temperature (Table IV). This is presumably due to the fact that trialkylamines are known to be poor... 

COPOLYMERIZATION OF BUTADIENE/STYRENE WITH LITHIUM MORPHOLINIDE IN HEXANE(a ... 

Copolymerization of butadiene and styrene in hexane with a number of initiators, such as lithium morpholinide, lithium dialkylamide, lithium piperidinide, etc., has also been examined. In general, the microstructure and styrene content of the polymers are dependent on the type of initiator and the polymerization conditions. Detailed results including a postulated mechanism for these polymerizations are discussed. 

Lithium diethylamide has been shown to be an effective initiator for the homopolymerization of dienes and styrene llr2). It is also known that such a polymerization process is markedly affected by the presence of polar compounds, such as ethers and amines (2,3). However, there has been no report of the use of a lithium amide containing a built-in polar modifier as a diene polymerization initiator. This paper describes the preparation and use of such an initiator, lithium morpholinide. A comparison between polymerization with this initiator and lithium diethyl amide, with and without polar modifiers, is included. Furthermore, we have examined the effects of lithium-nitrogen initiators on the copolymerization of butadiene and styrene. 

Lithium Morpholinide. Lithium morpholinide was the first one chosen as an initiator for butadiene-styrene copolymerization because of the built-in oxygen. It was felt that the presence of oxygen in the initiator may lead to a copolymer with unusual properties. 

From the Table IV, it also shows that the low styrene content in the copolymer may relate to the polymerization temperature. As the polymerization temperature was increased from 5° to 70°C, the styrene content of the butadiene-styrene copolymer decreased from 21.7% to 9.1%, respectively. The decreasing in styrene content at higher temperature is consistent with the paper reported by Adams and his associates (16) for thermal stability of "living" polymer-lithium system. In Adams paper, it was concluded that the formation of lithium hydride from polystyryllithium and polybutadienyllithium did occur at high temperature in hydrocarbon solvent. The thermal stability of polystyryllithium in cyclohexane is poorer than polybutadienyllithium. From these results, it appears that the decreasing in styrene content in lithium morpholinide initiated copolymerization at higher temperature is believed to be associated with the formation of lithium hydride. 

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