Fluorinated phenolic polymer, process for its preparation, and use thereof, particularly in the form of a film as a membrane in an electrolytic cell, said polymer consisting essentially of recurring units of(1) --CF.sub.2 CFX--wherein X in each of the recurring units is independently selected from F, Cl, R and OR wherein R is perfluoroalkyl of 1 to 4 carbon atoms and ##STR1## wherein Y is Cl, R or OR wherein R is perfluoroalkyl of 1 to 4 carbon atoms; M is H, alkali metal or NR'.sub.4 wherein R' in each of the recurring units is independently selected from H and alkyl of 1 to 6 carbon atoms; x is an average value within the range about 0.2 to about 1.0; n is 1, 2 or 3; and p is 0 or 1,said polymer having 0 to about 21 units of (1) per unit of (2).