Abstract: The invention concerns a novel catalytic combination for polymerizing alpha-olefins based on a titanium diamidide complex. The invention also concerns a method for polymerizing alpha-olefins using said catalytic combination, in the absence of any aluminum-containing compound. The inventive catalytic combination comprises: component A which is a dichlorinated titanium diamidide complex of general formula (I) wherein R represents a methyl group (component A2) or an isopropyl group (component A1); component B which is a dialkylmagnesium whereof the reaction with component A enables an alkylated component AA to be obtained: and as activator of said component AA, component C which is trispentafluorophenylboran (B(C6F5)3).

Abstract: The invention relates to unsymmetrical nanoscale or mesoscopic particles, and to a method for preparing the same. Said particles are characterized by a surface F1 and the zone Z2 carries groups F2 different from the groups F1, the zone Z1 being free of groups F2 and the zone Z2 being free of groups F1. The method of preparation comprises the following steps: 1) the zone Z2 of the surface of the initial particles is masked by fixing a polymer nodule thereto; 2) the masked particles obtained at the end of step 1) are treated in order to modify the nonmasked surface zone Z1 thereof; 3) the polymer nodule is removed after modifying the zone Z1; 4) optionally, the surface of the zone Z2 of the particles is modified following the demasking process.