Polymer production at supercritical conditions

A process to polymerize hydrocarbon olefins comprising contacting, under supercritical conditions, hydrocarbon olefin monomers with a Group 3-10 transition metal catalyst compound, an activator, optional comonomer, and optional hydrocarbon diluent or hydrocarbon solvent, in the presence of a fluorinated hydrocarbon absent fluoromonomers to provide a polymer comprising at least 75 mole % of hydrocarbon monomers, where the hydrocarbon olefin monomers are present in the polymerization system at 40 wt % or more, where the polymerization system is defined to be monomer(s) plus comonomer(s) plus fluorinated hydrocarbon(s), plus hydrocarbon solvent(s)/diluent(s) plus polymer product present.