Polymerisation of Aliphatic Monomers

Olefins and dienes are not polymerised by these acids. The addition products such as mr-butyl halides, are formed at different rates depending on the acid used and the reaction conditions (see Sect. III-B). However, propylene gives a certain amount of hexyl halides with HBr and HC1  

This behaviour can be rationalised in terms of a very fast collapse of the activated species formed in the attack of the acid molecule(s) onto the double bond, and/or by considering that the transition state is itself inactive towards propagation (tij t ion pair or polarised Ad S intermediate). The dimerisation of prc ylene could arise from some specific interaction, and is not to be considered as the first step in a cationic polyaddition because other oligomers have never been detected and the ceiling temperature of propylene is quite high. 

Recently, Sangalov et al. have reported that complexes of HCl with copper sulphate are effective heterogeneous catalysts for the oligomerisation of isobutene at room temperature. These authors claimed that the strength of the acid in considerably increased in the complex due to the loosening of the H—Cl bond. It seems to us that the heterogeneous nature of the catalyst must play an important role in fa- 

Vinyl ethers readily polymerise under the influence of dry hydrogen halides. This is understandable, given the high nucleophilicity of these monomers. It is regrettable that no kinetic or mechanistic study has ever been carried out on these potentially interesting systems. 

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