Alfin polymerization

Alfin polymerization of butadiene is unique in being a surface phenomenon. It is dependent upon specific components which must be present in proper proportions for the best reactions. Polymerization appears to be limited strictly to particular areas on the aggregate. These areas can be dispersed or poisoned by the presence of some compounds. Polymerization takes place by a radical mechanism, confined, however, to the surface where the monomer is adsorbed in a position ideal for polymerization. 

This paper will put together facts and ideas in Alfin polymerization which are related to the surface effects. The specific components of the reagent, their proportions, and their probable arrangement will be described. Polymerization will be interpreted as a phenomenon which occurs only on the surface and actually only on certain areas of that surface. Once started, chain growth does not spread to other areas or into solution, but remains on that particular area. In line with other catalysts, the Alfin reagent can be spread upon certain noncatalytic surfaces and can be poisoned by various salts or ions. The special features are further exemplified by the fact that the action is specific for extremely few monomers. Finally, a manner by which polymerization actually occurs on such a surface will be suggested. 

The alkoxide is equally specific in structure. According to the most recent data shown in Table II, the isopropoxide permitted the most effective use of allylsodium in polymerization of butadiene. The 3-pentoxide and cy-clohexoxide gave the highest ratio of trans 1,4- to 1,2-polymer. The f-bu-toxide also was effective to some degree, whereas in the first measurements, made under conditions less suitable for detecting Alfin activity, this salt caused no Alfin polymerization. Tests with -pentoxide had no effect and this fact also will be used in the discussion under Section III. 

Effect of Different Metalated Hydrocarbons on Alfin Polymerization of Butadine... 

This proposition can be differentiated from the previous one by stating that Alfin polymerization, once started, does not spread to other areas or into the solution. The facts confirming this view have already been published 6) but deserve special mention for their great importance to this paper on surface effects. 

Naphthylmethylsodium does not itself induce Alfin polymerization but can act as a support or extender for an Alfin reagent. When mixed in equal quantities (1 mole of allylsodium to 1 mole of naphthylmethylso-dium), the capacity of the reagent is doubled or tripled (9). Polymerization does not spread to the naphthylmethylsodium but remains the same as for the Alfin catalyst alone. That is to say, the viscosity and the ratio of trans-... 

Any proposal for the manner of Alfin polymerization of butadiene must conform to the requirements of a special surface, as just described. Initiation can be assumed to take place by coordination of the diene about a sodium cation followed by dissociation of the salt to two radicals. A dissociation of... 

Eventually the growing point makes contact with the other radical produced from the original dissociation of the salt. Alfin polymerization therefore appears to involve long-chain growth between the reactivity of two radicals derived from dissociation of an organosodium salt. Radioactive measurements IS) are in accord with the view that both components of a salt are present in each chain. 

In fact, we believe that alfin polymerizations are anionic rather than free... 

The long-known alfin polymerization of butadiene recently has also become important industrially. The alfin catalyst is so called because it originally resulted from the transformation of an alcohol and an olefin (e.g., sodium isopropylate and alkyl sodium). Commercially, the best means of producing the catalysts is to proceed from isopropanol, sodium, and w-butyl chloride ... 

The alfin polymerization yields extremely high-molar mass poly (butadienes) with 65%-75% transAA structures. 1,4-Dihydro benzene or 1,4-dihydro-naphthalene serve as regulators to control the molecular weights. Industrially produced butadiene copolymers contain 5%-15% styrene or 3%-10% isoprene. 

Alfin polymerization n. The Alfin catalyst (Hans-Georg Elias (1977) Macromolecules, Plenum Press, New York), consists of a suspension in an inert solvent like pentane of a mixture of an alklenylsodium compound (such as allyl sodium), an alkoxide of a secondary alcohol (such as isoproxide), and an alkali halide (such as sodium chloride) the catalyst is highly specific for the polymerization of dienes into the 1,4 forms. 

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