Abstract: The present invention provides to a catalytic system, its method for preparation, and a method for preparation of a copolymer of ethylene and a conjugated diene, which uses this catalytic system. A catalytic system according to the invention comprises: an organometallic complex compound, which is represented by one formula A or B: in which Ln represents a metal of a lanthanide, the atomic number of which is between 57 and 71; X represents a halogen, which can be chlorine, fluorine, bromine or iodine; and Cp1 and Cp2 each comprise a cyclopentadienyl or fluorenyl group, which is or is not substituted, and P is a bridge corresponding to the formula MR2, in which M is an element of column IVA of Mendeleev's periodic classification, and R is an alkyl group comprising from 1 to 20 atoms of carbon; and a co-catalyst selected from among a magnesium alkyl, a lithium alkyl, an aluminium alkyl, or a Grignard's reagent, and mixtures thereof.

Abstract: The present invention relates to a cross-linkable or cross-linked rubber composition having improved hysteresis properties in the cross-linked state which is useful for the manufacture of treads for tires. The rubber composition of the present invention comprises at least one diene elastomer having a molar ratio of units originating from conjugated dienes which is greater than 30% and comprising carboxylic acid functions along its chain, and a reinforcing inorganic filler. The present invention further relates to a process for preparing such a cross-linkable or cross-linked rubber composition as well as to a tire having reduced rolling resistance and a tread for a tire where the tread comprises the rubber composition of the present invention.

Abstract: The present invention provides to a catalytic system, its method for preparation, and a method for preparation of a copolymer of ethylene and a conjugated diene, which uses this catalytic system. A catalytic system according to the invention comprises: an organometallic complex compound, which is represented by one formula A or B:  in which Ln represents a metal of a lanthanide, the atomic number of which is between 57 and 71; X represents a halogen, which can be chlorine, fluorine, bromine or iodine; and Cp1 and Cp2 each comprise a cyclopentadienyl or fluorenyl group, which is or is not substituted, and P is a bridge corresponding to the formula MR2, in which M is an element of column IVA of Mendeleev's periodic classification, and R is an alkyl group comprising from 1 to 20 atoms of carbon; and a co-catalyst selected from among a magnesium alkyl, a lithium alkyl, an aluminium alkyl, or a Grignard's reagent, and mixtures thereof.

Abstract: The present invention provides to a catalytic system, its method for preparation, and a method for preparation of a copolymer of ethylene and a conjugated diene, which uses this catalytic system.