| abstract |
This dialkylmagnesium is represented by the formula: R- (CH 2 -CH 2 ) n -Mg- (CH 2 -CH 2 ) n , -R ', (EO-E') x ' where R and R' each independently represent a C 1 -C 20 hydrocarbon residue, branched or not, substituted or unsubstituted, of the alkyl, cycloalkyl or aralkyl type; n and n ′, identical or substantially identical, represent an average number of sequences -CH 2 -CH 2 - such that the average number of carbon atoms in each of the two chains carried by Mg is greater than 20; E and E ', identical or different, each represent an alkyl radical, linear or cyclic, branched or not; and 0 ≤ x ≤ 2, x being the mean value of the number of moles of EOE ether complexed with dialkylmagnesium. To prepare a dialkylmagnesium of this type, in an anhydrous and deoxygenated hydrocarbon solvent, ethylene is polymerized using a catalyst Cp * 2 MCl 2 Li (OEt 2 ) 2 (Cp * = pentamethylcyclopentadienyl ligand; M = scandium, yttrium or metal of the lanthanide series; Et = ethyl), in the presence of a dialkylmagnesium, soluble in said solvent, of formula R - Mg - R ', (EO-E') x ' where R, R ', E, E' and x are as defined above, as chain transfer agent, and the reaction is stopped before the polydispersity of the obtained polymer product exceeds 2, preferably 1.5. |