A fluorine-containing ??,??-bifunctional compound having the formula: ##STR1## wherein each of R1 and R2 independently is a hydrogen atom, an alkyl group or an aralkyl group; X is --COOH, --COOR3, --COY or --NCO, wherein R3 is an alkyl group or an aralkyl group and Y is a halogen atom or N3 ; and n is an integer of at least 1 provided that when X is --COOH, n is an integer of at least 4.