Abstract: A process for the preparation of polymers containing peroxide end-groups, in which one or more monomers, particularly alpha-olefins, are polymerized by means of a co-ordination catalyst in the presence of an adjuvant with the formula M(X)p, where M is boron or a metal in column IIb of the Periodic Table of Elements, p is the valency of M, and X is at least one monovalent organic radical, a hydrogen atom or a halogen, the polymer obtained is treated with a peroxidizing agent, without being de-activated, and the resulting polymer containing peroxide groups is collected.Polymers with peroxide end-groups obtained by this process, particularly olefins with peroxide end-groups, can be used to initiate polymerization of vinylic monomers, and are accordingly useful in the synthesis of block copolymers, in which one part is formed from the polymeric part of the macromolecular peroxide and the other part is derived from the vinylic monomer or monomers polymerized by means of this peroxide.

Abstract: This invention concerns a process for polymerizing ethylenic monomers in aqueous suspension, characterized by the use, as suspension agent, of an inorganic precipitate obtained by coprecipitating a mixture of soluble phosphate and carbonate containing at least 1 gram-ion of CO.sub. 3 .sup.-.sup.- to 3 gram-ions of PO.sub.4 .sup.-.sup.-.sup.- with a soluble salt of the metals in columns IIa and IIb of the periodic table of elements, or of aluminum or iron.Styrene is preferably polymerized in the presence of a precipitate obtained by the action of calcium caloride on a mixture of sodium phosphate and carbonate containing between 1 gram-ion of CO.sub.3 .sup.-.sup.- to 2 gram-ions of PO.sub.4 .sup.-.sup.-.sup.- and 2 gram-ions of CO.sub.3 .sup.-.sup.- to 3 gram-ions of PO.sub.4 .sup.-.sup.-.sup.- .The spherical particles of polymer obtained are particularly suitable for the manufacture of expanded polymers.