h is an acyclic olefin monomer of the formula VIII ##STR21## in which R9, R10, R11 and R12 are identical or different and are a hydrogen atom or a C1 -C6 -alkyl radical,said polymerizing being carried out at a temperature of from -78??? to 150??? C., at a pressure of 0.01 to 64 bar, in a substantially constant first monomer:second monomer incorporation ratio which provides substantial chemical hom