A method of coating a polymer comprising the step of treating the polymer with an activating agent to produce a reactive polymer, for example treating a polymer bearing at least one X (halogen) group and at least one H with base to eliminate HX. The reactive polymer is then reacted with a reactive coating, for example PVP, preferably in the presence of an initiator like persulfate anions, to produce a coated polymer, which may be hydrophilic in nature.