Patent ID: 8193393

Claim:
A compound having the formula, Rf 1 -C(O)CF(Rf 2 )(O) a Rf 3 (O) b CF(Rf 4 )C(O)Rf 1 , wherein Rf 1 =a perfluoroalkyl group that is branched, cyclic, or a combination thereof, that, optionally, contains at least one in-chain oxygen or nitrogen heteroatom, Rf 2 and Rf 4 =—F or —CF 3 , Rf 3 =a perfluoroalkylene moiety which may be linear, branched or cyclic having from 4 to 9 carbon atoms which may be interrupted by at most one in-chain divalent ether oxygen atom at least one of Rf 2 or Rf 4 is CF 3 —, a and b are independently 0 or 1 and a+b≧1, with the proviso that Rf 3 does not contain —OCF 2 CF 2 O—.