Lithium diethylamide, styrene

The need for solvation in anionic polymerization manifests itself in some instances by other deviations from the normal reaction rate expressions. Thus the butyllithium polymerization of methyl methacrylate in toluene at — 60°C shows a second-order dependence of Rp on monomer concentration [L Abbe and Smets, 1967]. In the nonpolar toulene, monomer is involved in solvating the propagating species [Busson and Van Beylen, 1978]. When polymerization is carried out in the mixed solvent dioxane-toluene (a more polar solvent than toluene), the normal first-order dependence of Rp on [M] is observed. The lithium diethylamide, LiN(C2H5)2, polymerization of styrene at 25°C in THF-benzene similarly shows an increased order of dependence of Rp on [M] as the amount of tetrahydrofuran is decreased [Hurley and Tait, 1976]. 

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. 

The copolymerizations of butadiene and styrene with these four amides were carried out in hexane with the insoluble initiators at several different temperatures. In general, the styrene content in the lithium diethylamide or lithium di-n-butylamide initiated butadiene-styrene polymerizations is higher than in the lithium dimethylamide or lithium di-i-propylamide system (Table VII). A high styrene content (23.4% to 25.3%) in the lithium diethylamide and the lithium di-n-butylamide systems was obtained at 50°C polymerization temperature. From this result, it appears that the best copolymerization temperature for these systems is 50 C. 

In 1973, Tsuruta and his coworkers79) established that diethylamine adds stoichio-metrically to styrene in the presence of some lithium diethylamide. The reaction mechanism involves two steps namely a kind of anionic initiation and subsequent proton transfer, due to the difference in the acidity between the benzylic and amine substrate ... 

As the writer reported previously, lithium diethylamide, in the presence of diethylamine, underwent the one to one addition reaction with styrene (5) or divinylbenzene (DVB) (6). No reaction, however, took place between lithium diisopropylamide and styrene. A surprising result, in contrast, was obtained in... 

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