Anne Macedo

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.

Cationic polymerization of 1,3-pentadiene initiated with aluminium chloride in non-polar solvent : study of the initiation mechanism

SUMMARY The cationic polymerization of 1,3-pentadiene initiated with aluminium chloride was studied in a non-polar solvent. Experiments carried out in the presence of 2,6-di-tert-butylpyridine (DtBP) clearly demonstrated that the major initiation process is the direct initiation mechanism, even though the existence of a cocatalytic mechanism to small extent cannot be rejected. This result is also evidenced by the linear dependence of the conversion on A1C13 concentration, and by experiments carried out in the presence of hydrogen chloride showing the independence of the polymerization yield on the hydrogen chloride concentration.

Cationic polymerization of 1,3-pentadiene: IV. Initiation by aluminum chloride in an apolar solvent: effect of various electron donors

Abstract The polymerization of 1,3-pentadiene (PD) initiated by aluminum trichloride in nonpolar solvent was carried out in the presence of various electron donors (EDs) such as ethyl acetate, (EtOAc) tert -butyl acetate, dimethyl phthalate (DMP), N , N -dimethyl formamide, N , N -dimethyl acetamide and dimethyl sulfoxide. Addition of an ED whatever its nature to the polymerization medium, in a one-to-one molar ratio relatively to the Lewis acid, resulted in a decrease of the overall yield and an increased proportion of crosslinked polymer. The molecular weight distribution of the soluble fraction was narrower than that of polymerizations carried out without ED. The microstructure of the soluble polymers can be tuned using different EDs, showing that they are interacting with the active species. For instance EtOAc increased polymer isomerization while DMP increased polymer cyclization. Thus, the nature of the chemical functions borne by the ED does not seem to be the only parameter explaining its influence on the polyPD microstructure. If crosslinking efficiency seems to be roughly correlated to the donicity scale of the EDs, termination reaction is not. It was shown that the complexation between the Lewis acid and the EDs containing a carbonyl group involved the carbonyl oxygen atom. The decrease of polymerization yield when using the EDs was assigned to this complexation between the ED and AlCl 3 .