Compounds of formula I: wherein X are independently —(CH2)b—, wherein b is 0 or an integer from 1 to 6; Rf are independently —CF2O(CF2CF2O)p(CF2)qCF2—, —CF2CF2O(CF2CF2CF2O)rCF2CF2—, or —CF2CF2CF2O(CF2CF2CF2CF2O)sCF2CF2CF2—, or derivatives thereof, wherein p, q, r and s are independently integers so that Mn of Rf is about 150 to 4500; and Z are independently chosen from groups that comprise —OH, —(OH)2, —COOCH3, —F, —CF3, or —CF2CF3, with the caveat that not all Z are the same.