Abstract: Isoprene polymers and copolymers are prepared by a polymerization process carried out in the absence of solvents and in the presence of a catalytic system comprising (a) at least one element or compound of an element pertaining to Group IIIB of the Periodic Table, (b) at least one aluminium alkyl derivative, (c) at least one organic halogen derivative or at least one halide of an element able to exist in at least two valency states with the halide corresponding to a higher state than the minimum, or at least one halogen or at least one hydrogen halide acid, (d) at least one compound containing one or more hydroxyl groups of which the hydrogen can be substituted, the ratio of component (b) to component (a) being equal to or less than 20.

Abstract: A new process is described for polymerizing and copolymerizing conjugate diolefins characterized by the use of a catalytic system comprising at least one compound of Group III B of the periodic system, at least one non-halogenated aluminium alkyl, at least one compound containing one or more hydroxyls of acid or neutral type, and possibly an inorganic compound containing Cl or Br in ionizable form or an organic halogen derivative.The new process allows the preparation, both in the absence and in the presence of an inert diluent, of polydiolefins of essentially entirely 1,4-cis structure which even in the absence of a purification stage contain a very small quantity of catalytic residues.

Abstract: An improved process is described for preparing conjugate diolefin polymers or copolymers having a high content of 1,4-cis units and high chain linearity, the process using a particular catalytic system prepared from a compound of a metal chosen from those of Group III B of the Periodic System which have an atomic number of between 21 and 103, preferably neodymium, an organic halogen derivative, and an aluminium alkylhydride or trialkyl.