Cationic isomerization polymerization of 3,3‐dimethyl‐1‐butene

Abstract

The cationic polymerization of 3,3-dimethyl-l-butene (t-butyl ethylene) has been investigated. Polymerizations were carried out with AlCl, catalyst in ethyl chloride solvent in the temperature range -31 to -130°C. Trimers (viscous oils or soft gels) were obtained between -31 and -100 "C. The composition and strwture of these materials is complicated and remains obscure. Solid polymer was obtained only a t -130°C. This material, whose degree of polymerization is -68, is a white amorphous powder and it melts between 55 and 66 "C. It is soluble in most common solvents.Careful NMR and I R spectroscopic studies indicate that the repeat structure of this polymer is :

The Most Well-Known Rearrangements in Organic Chemistry at Hand

“…For example, the polymerization of 3-methyl-1-butene with coordination catalysts (Ziegler-Natta) yields the conventional 1,2-polymer. However, with Lewis acids as initiators at -130°C, the polymerization of this monomer gives a high molecular weight and crystalline 1,3-polymer which results from a hydride shift, a structure actually suggested by 1 H NMR spectrum revealing two singlet peaks [22]. Interesting is the fact that, at relatively high temperature (-100°C), a copolymer of 1,2 and 1,3 units is obtained as an amorphous material.…”

“…In the latter case, an allylic carbonium ion rearrangement is involved. (22) Not only in low molecular weight substances has the allylic rearrangement been observed, but also in high molecular weight analogues, the polymeric systems. The halogenation of butyl rubber (polyisoprene) comes up with exo-and endo-allylic structure halobutyl rubber as traced in equation (23).…”

Carbocationic Polymerization

“…Intermolecular reactions involving two or more polymer chains lead to branching-see Figure 9b. Isomerization by hydride or alkyl transfer (157,158) leading to more stable carbenium ions can also be considered as a form of chain transfer. The protons or new active sites forming in chain-transfer reactions can initiate new chains.…”

Developments in the Field of Isomerization Polymerizations*

“…The only well documented case of a group migration polymerization is that of the cationic polymerization of 3,3-dimethylbutene-l. 44 The polymerization of this monomer has been investigated at moderately low temperature (-30 to -100°C) by several workers,36,45 but only oligomers, mostly trimers, have been obtained. However, in our laboratories we found that high molecular weight polymers can be synthesized readily provided the temperature is lowered to about -13OOC.…”

“…However, in our laboratories we found that high molecular weight polymers can be synthesized readily provided the temperature is lowered to about -13OOC. 44 Failure to obtain high molecular weight product at higher temperatures can be attributed to slow propagation and t o severe steric hindrance around the growing site. Molecular models indicate that the unrearranged carbonium ion B ;H3 -*rc1:…”