Zero valent metal initiated gas-phase deposition polymerization

A process for polymerizing a radically polymerizable monomer or a mixture of two or more radically polymerizable monomers in a reactor to form a polymer, said process comprising contacting at least one zero valent transition metal selected from groups 3 to 12 of the periodic system of elements with an initiator having one or more radically transferable atoms or groups, wherein the radically polymerizable monomer or monomers are introduced into the reactor in the gas-phase and the reactor is at a temperature where the radically polymerizable monomer or monomers are present in the gas-phase during polymerization, wherein the molar ratio of zero valent metal to N—, O—, P— or S-containing ligands which coordinate in a σ-bond or a π-bond to the zero valent transition metal and are not built into the polymer or the amount of C-containing compounds which can coordinate in a π-bond to the zero valent transition metal and are not built into the polymer is more than 1:1, and wherein said zero valent transition metal is present on a substrate having an at least partially metallic surface.