The substrate of claim 25 wherein said fluorochemical compound which contains a single functional group is represented by the formula: Rf???Rk???R2???X??????H wherein Rf is a monovalent aliphatic group containing at least two carbon atoms each of which is attached to at least two fluorine atoms; R is the divalent radical: ???CmH2mSO???, ???CmH2mSO2???, ???SO2N(R3)???, or ???CON(R3)??? in which m i