Abstract: The present invention provides a process for making fluorinated polymers and copolymers having stable end groups. The process includes (1) contacting a fluoromonomer, an initiator capable of producing stable end groups on the polymer chain, and a polymerization medium comprising carbon dioxide, and (2) polymerizing the fluoromonomer. The polymerization medium preferably comprises liquid or supercritical carbon dioxide. Advantageously, the process may also include the step of separating the fluoropolymer from the polymerization medium. The present invention also provides polymerization reaction mixtures useful in the processes of the present invention.