Disclosed are copolymers which are useful in hydrophilically modifying porous fluoropolymer supports. An example of the copolymers is: Also disclosed are a method of preparing such copolymers, a method of modifying porous fluoropolymer surfaces, and hydrophilic fluoropolymer porous membranes prepared therefrom. Also disclosed is a method of filtering fluids by the use of the hydrophilic fluoropolymer porous membranes.