sents the unit derived from the opening of the double bond of a molecule of hexafluoropropylene, the diiferent perfiuoroalkylene units having a random distribution along the polymer chain, and R is selected from the group consisting of OH, OR CN, and --NR R wherein R is a radical containing from 1 to 12 carbon atoms, and is alkyl, alkylaryl, aryl, cycloalkyl or is the corresponding halogen-substit