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 prese nce of ferric chloride, in hexane. It was demonstrated that initiation was due to cocatalysis by water. From the bimodality of the polymer, it was con cluded that initiation was mixed, i.e. mainly homogeneous at high PD concen tration and heterogeneous at low PD concentration. Polymerization produced a fraction of crosslinked polymer which results from gellification of the h ighest molecular weight macromolecules. The E monomer did not produce cross linked material and appeared to be more reactive than the Z one. Cyclizatio n was found to be mainly due to an intramolecular process. The monomer conv ersion remained incomplete, except for the highest ferric chloride concentr ations. A study of the polymerization yield in various conditions showed th at the termination reactions are of two types: bimolecular due to the react ion of active centers with macromolecules unsaturations, and a unimolecular reaction of the active site with the counteranion, both reactions producin g a chlorinated polymer. A chemical analysis of the chlorinated functions b orne by the PPD showed that there are of two types in agreement with the pr eceding conclusion, (C) 2000 Elsevier Science Ltd. All rights reserved.