Cationic polymerization of dienes III. Polymerization of 1,3-pentadiene initiated by ferric chloride in hexane

The cationic polymerization of 1,3-pentadiene (PD) was studied in the presence of ferric chloride, in hexane. It was demonstrated that initiation was due to cocatalysis by water. From the bimodality of the polymer, it was concluded that initiation was mixed, i.e. mainly homogeneous at high PD concentration and heterogeneous at low PD concentration. Polymerization produced a fraction of crosslinked polymer which results from gellification of the highest molecular weight macromolecules. The E monomer did not produce crosslinked material and appeared to be more reactive than the Z one. Cyclization was found to be mainly due to an intramolecular process. The monomer conversion remained incomplete, except for the highest ferric chloride concentrations. A study of the polymerization yield in various conditions showed that the termination reactions are of two types: bimolecular due to the reaction of active centers with macromolecules unsaturations, and a unimolecular reaction of the active site with the counteranion, both reactions producing a chlorinated polymer. A chemical analysis of the chlorinated functions borne by the PPD showed that there are of two types in agreement with the preceding conclusion.